##### Class 10^{th} Science Gujarat Board Solution

**Exercise**- The SI unit of electric charge is......A. ampere B. volt C. watt D. coulomb…
- What number of electrons will be there in 1.6 C charge?A. 10^17 B. 10^18 C. 10^19 D. 10^20…
- 1μA = --------- mA.A. 10-16 B. 10-3 C. 10^3 D. 10^6
- Which of the following materials has more number of free electrons?A. Copper B. Glass C.…
- According to Ohm’s law,A. The resistance increases with the increase in current. B. The…
- The formula for an electric current is -----.A. I = Qt B. I = C. I = D. I = Wt…
- The amount of 2 A electric current is passed for 1 minute through one conducting wire. How…
- In an electrical appliance, the electric current of 4.8 A is passed, then the number of…
- Which of the following formula represents the voltage?A. B. C. Work X electric charge D.…
- The unit of electric potential difference is ---------A. J B. J/C C. 5 V D. 45 V…
- If the work is to be done to take 3C electric charge from one point to another is 15 J,…
- The resistance of one conducting wire is 10 Ω. How much electric current will flow by…
- On which factors does the resistivity of conducting wire depend?A. Length of wire B. Area…
- If the five equal pieces of a resistance wire having 5 resistance each is connected in…
- The unit of resistivity of the material is -A. B. m C. /m D. m/
- What will be the resistance between points A and B of the following electric circuit? A. 1…
- What will be the equivalent resistance between points A and B of the following electric…
- The equivalent resistance between points A and B in the following electric circuit is.…
- Which physical quantity has a unit of kWh?A. Work B. Electric power C. Electric current D.…
- 1kWh = --------jouleA. 3.6 x 10^6 B. 3.6 x 10^3 C. 3.6 x 10-6 D. 3.6 x 10-3…
- An electric heater consumes 1.1 kW power when 220 V voltage applied to it. How much…
- What makes the electric current flow through electric solution?A. Only free electrons B.…
- The distilled water acts as ----- for the electricity.A. Conductor B. Insulator C.…
- What is an electric charge? Give its types and write is unit.
- What is a free electron? Explain conducting and non-conducting materials in terms of it.…
- Give the definition of an electric current and define its unit.
- Give advantages of series and parallel connection of resistors.
- Write Faraday’s laws of electrolysis.
- What is an electric potential? Give the definition and unit of electric potential.…
- Explain the series connections of resistors and derive the formula of equivalent…
- Explain the parallel connection of resistance and drive the formula of equivalent…
- Explain electrical energy and drive its formula.
- Draw the figure of voltaic cell and explain its construction. Explain flow of current in…
- What is electrolyte? Describe the experiment showing flow of current in electrolyte.…
- Write Ohm’s law. Describe the experiment showing Ohm’s law and write its conclusions.…
- What is electroplating? Explain it with example.
- If 400 mA current flows through the bulb for 1 minute, how many electrons will pass…
- The 1800 C electric charge is passing through an electric bulb in one hour. How much…
- The three resistance of resistance 5 Ω, 10 Ω and 30 Ω are connected with a 12 V battery in…
- As shown in the figure the resistance are connected with a 12 V battery. Determine (a)…
- Find the electric current in the following circuit:
- Determine the equivalent resistance between points X and Y in the following circuit.…
- Two lamps of 100 W and 60 W are joined in parallel with 220 V lines. How much current will…
- An electric heater consumes 4.4 kW power when connected with a 220 V lines voltage then,…

**Exercise**

- The SI unit of electric charge is......A. ampere B. volt C. watt D. coulomb…
- What number of electrons will be there in 1.6 C charge?A. 10^17 B. 10^18 C. 10^19 D. 10^20…
- 1μA = --------- mA.A. 10-16 B. 10-3 C. 10^3 D. 10^6
- Which of the following materials has more number of free electrons?A. Copper B. Glass C.…
- According to Ohm’s law,A. The resistance increases with the increase in current. B. The…
- The formula for an electric current is -----.A. I = Qt B. I = C. I = D. I = Wt…
- The amount of 2 A electric current is passed for 1 minute through one conducting wire. How…
- In an electrical appliance, the electric current of 4.8 A is passed, then the number of…
- Which of the following formula represents the voltage?A. B. C. Work X electric charge D.…
- The unit of electric potential difference is ---------A. J B. J/C C. 5 V D. 45 V…
- If the work is to be done to take 3C electric charge from one point to another is 15 J,…
- The resistance of one conducting wire is 10 Ω. How much electric current will flow by…
- On which factors does the resistivity of conducting wire depend?A. Length of wire B. Area…
- If the five equal pieces of a resistance wire having 5 resistance each is connected in…
- The unit of resistivity of the material is -A. B. m C. /m D. m/
- What will be the resistance between points A and B of the following electric circuit? A. 1…
- What will be the equivalent resistance between points A and B of the following electric…
- The equivalent resistance between points A and B in the following electric circuit is.…
- Which physical quantity has a unit of kWh?A. Work B. Electric power C. Electric current D.…
- 1kWh = --------jouleA. 3.6 x 10^6 B. 3.6 x 10^3 C. 3.6 x 10-6 D. 3.6 x 10-3…
- An electric heater consumes 1.1 kW power when 220 V voltage applied to it. How much…
- What makes the electric current flow through electric solution?A. Only free electrons B.…
- The distilled water acts as ----- for the electricity.A. Conductor B. Insulator C.…
- What is an electric charge? Give its types and write is unit.
- What is a free electron? Explain conducting and non-conducting materials in terms of it.…
- Give the definition of an electric current and define its unit.
- Give advantages of series and parallel connection of resistors.
- Write Faraday’s laws of electrolysis.
- What is an electric potential? Give the definition and unit of electric potential.…
- Explain the series connections of resistors and derive the formula of equivalent…
- Explain the parallel connection of resistance and drive the formula of equivalent…
- Explain electrical energy and drive its formula.
- Draw the figure of voltaic cell and explain its construction. Explain flow of current in…
- What is electrolyte? Describe the experiment showing flow of current in electrolyte.…
- Write Ohm’s law. Describe the experiment showing Ohm’s law and write its conclusions.…
- What is electroplating? Explain it with example.
- If 400 mA current flows through the bulb for 1 minute, how many electrons will pass…
- The 1800 C electric charge is passing through an electric bulb in one hour. How much…
- The three resistance of resistance 5 Ω, 10 Ω and 30 Ω are connected with a 12 V battery in…
- As shown in the figure the resistance are connected with a 12 V battery. Determine (a)…
- Find the electric current in the following circuit:
- Determine the equivalent resistance between points X and Y in the following circuit.…
- Two lamps of 100 W and 60 W are joined in parallel with 220 V lines. How much current will…
- An electric heater consumes 4.4 kW power when connected with a 220 V lines voltage then,…

###### Exercise

**Question 1.**The SI unit of electric charge is......

A. ampere

B. volt

C. watt

D. coulomb

**Answer:**In SI unit system, charge is measured in Coulomb(C)

Charge on electron = -1.6 × 10^{-19}C

**Question 2.**What number of electrons will be there in 1.6 C charge?

A. 10^{17}

B. 10^{18}

C. 10^{19}

D. 10^{20}

**Answer:**As 1C = Electrons

**Question 3.**1μA = --------- mA.

A. 10^{-16}

B. 10^{-3}

C. 10^{3}

D. 10^{6}

**Answer:**μA = 10^{-6}A

mA = 10^{-3}A

**Question 4.**Which of the following materials has more number of free electrons?

A. Copper

B. Glass

C. Rubber

D. Iron

**Answer:**As metals has most number of free electrons and from the choice above copper and iron are metals.

But when we know that more the current flowing in a conductor more are the free electrons. So, copper being a very good conductor has more number of free electrons.

**Question 5.**According to Ohm’s law,

A. The resistance increases with the increase in current.

B. The resistance increases with the increase in voltage.

C. The current increases with the increases in voltage.

D. The resistance and current both increase with the increase in voltage.

**Answer:**The Ohm’s Law state that, the potential difference (voltage) across an ideal conductor is proportional to the current through it. The constant of proportionality is called the "resistance", R. Ohm's Law is given by: V = I R where V is the potential difference between two points which include a resistance R.

**Question 6.**The formula for an electric current is -----.

A. I = Qt

B. I =

C. I =

D. I = Wt

**Answer:**Electric current means rate of flow of an electric charge.

**Question 7.**The amount of 2 A electric current is passed for 1 minute through one conducting wire. How much total electric charge will pass through this wire?

A. 2 C

B. 30 C

C. 60 C

D. 120 C

**Answer:**1 minute = 60 sec.

I = & I = 2A.

2 = . So, Q = 120C

**Question 8.**In an electrical appliance, the electric current of 4.8 A is passed, then the number of electrons passing through it in one second will be ------------

A. 0.33 x 10^{19}

B. 3.3 x 10^{19}

C. 3 x 10^{19}

D. 4.8 x 10^{19}

**Answer:**Given I = 4.8 T = 1sec

Using I = we get Q = 4.8C

Since 1C = electrons

So, 4.8C = = 3 x 10^{19} electrons

**Question 9.**Which of the following formula represents the voltage?

A.

B.

C. Work X electric charge

D. Work x electric charge x time

**Answer:**Voltage is defined as Work done per unit charge.

V =

Charge = I x T

**Question 10.**The unit of electric potential difference is ---------

A. J

B. J/C

C. 5 V

D. 45 V

**Answer:**Voltage is defined as Work Done per unit charge.

V =

**Question 11.**If the work is to be done to take 3C electric charge from one point to another is 15 J, what will be the potential difference between these two points?

(A) 3 V

(B) 15 V

(C) 5 V

(D) 45 V

**Answer:**We know that potential difference b/w any two points is work done to carry charge from one point to another. So,

**Question 12.**The resistance of one conducting wire is 10 Ω. How much electric current will flow by connecting it with a batter of 1.5 V?

A. 0.15 mA

B. 1.5 mA

C. 15 mA

D. 150 mA

**Answer:**V = I x R

V = 1.5V & R = 10 Ω

Hence 1.5V = 10 Ω x I

I = 150 mA

**Question 13.**On which factors does the resistivity of conducting wire depend?

A. Length of wire

B. Area of cross-section of wire

C. Volume of wire

D. Material of wire

**Answer:**Resistivity depends only on material of wire.

**Question 14.**If the five equal pieces of a resistance wire having 5 resistance each is connected in parallel, then their equivalent resistance will be -----

A. 1/5

B. 1

C. 5

D. 25

**Answer:**When resistance is connected in parallel we use the following formula

**Question 15.**The unit of resistivity of the material is –

A.

B. m

C. /m

D. m/

**Answer:**R(Ω) = ρ x

**Question 16.**What will be the resistance between points A and B of the following electric circuit?

A. 1

B.2

C. 5

D. 10

**Answer:**Since all the resistance are in series, so total resistance will be sum of all the resistance.

**Question 17.**What will be the equivalent resistance between points A and B of the following electric circuit?

A. 4

B. 8

C.2

D 16

**Answer:**The two 4Ω resistance are in series & are in parallel to 8Ω resistance.

R1 = 8Ω & R2 = 8Ω

**Question 18.**The equivalent resistance between points A and B in the following electric circuit is. ---.

A.2.5

B.5

C. 12.5

D. 20

**Answer:**The two 5Ω resistors are in parallel which is results in 2.5Ω in series with the other two 5Ω resistors.

Parallel

**Question 19.**Which physical quantity has a unit of kWh?

A. Work

B. Electric power

C. Electric current

D. Electric potential.

**Answer:**It is called kilowatt hour and is a unit for energy and is especially used in electricity bills.

**Question 20.**1kWh = --------joule

A. 3.6 x 10^{6}

B. 3.6 x 10^{3}

C. 3.6 x 10^{-6}

D. 3.6 x 10^{-3}

**Answer:**1 kilowatt hour

1 hour = 3600 seconds

1killo = 1000

1 kilowatt hour = 3600000 = A. 3.6 x 10^{6}

**Question 21.**An electric heater consumes 1.1 kW power when 220 V voltage applied to it. How much current will be flowing through it?

A. 1.1 A

B. 2.2 A

C. 4 A

D. 5 A

**Answer:**Power = Voltage x Current; Power = 1.1kW = 1100W

Voltage = 220 V

Hence, Current

**Question 22.**What makes the electric current flow through electric solution?

A. Only free electrons

B. Only positive ions.

C. Only negative ions

D. Positive and negative ions.

**Answer:**The solution that conducts electricity are called “electrolytes”. In electrolytes, the electric current flows due to both positive and negative ions.

**Question 23.**The distilled water acts as ----- for the electricity.

A. Conductor

B. Insulator

C. Semiconductor

D. None.

**Answer:**In distilled water there is no free positive or negative ions hence it acts as an insulator.

**Question 24.**What is an electric charge? Give its types and write is unit.

**Answer:**Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charges are of two types: Positive electric charge (proton) & negative electric charge (electron). Electric charge is an intrinsic (independent) property of electron and proton like mass.

The SI unit of electric charge is Coulomb.

**Question 25.**What is a free electron? Explain conducting and non-conducting materials in terms of it.

**Answer:**In atoms, electrons move around the nucleus where protons remain bound. In some material like metals, under normal circumstances, the attractive force between the valence electrons (outermost ones) and nucleus is comparatively very small.

During the formation of metallic materials, these electrons get separated from their parent atom and move in a random manner. Such electrons are known as Free electrons.

These free electrons are responsible for their electricity conducting property.

**Question 26.**Give the definition of an electric current and define its unit.

**Answer:**The net quantity of an electric charge flowing through any cross-section of conductor is defined as electric current.

Thus,

The SI unit of current is Ampere (A).

**Question 27.**Give advantages of series and parallel connection of resistors.

**Answer:**The total resistance of the circuit increases by connecting the resistors in series hence, the current decreases. Thus, to control the current in the circuit, series connection of resistors is useful. Moreover, the fuse is always connected in series with the mains. Therefore, whenever there is short circuit in any electrical appliance, the fuse wire melts and stops electric current. As a result, damage to electrical appliance can be prevented.

Whereas, the advantage of parallel connection is that when we connect three bulbs in parallel all will get equal voltage and therefore will give equal amount of light irrespective of each other. Secondly, if any appliance is affected/fused, it will not affect the other appliance. When we need more current we use parallel connection as resistance gets decreased resulting in more amount of current.

**Question 28.**Write Faraday’s laws of electrolysis.

**Answer:**On passing the electric current through electrolytic solution, negative charge moves towards positive terminal and positive ions towards negative terminal. This process of separating the ions is called __electrolysis__.

__Faraday’s First Law__ – The mass of substance (metal) deposited at cathode on passing electric current through electrolytic solution is proportional to charge passing through it, M ∝ Q

__Faraday’s Second Law__ – For a given amount of current passed, the masses of different elements deposited on cathode is proportional to their chemical equivalent (e).

**Question 29.**What is an electric potential? Give the definition and unit of electric potential.

**Answer:**On bringing some electric charge near any other charge, an attractive or repulsive force exerts on it. Thus, the work is to be done against this force keeping a charge in equilibrium and to move another near or far from it. This work is stored in the form of potential energy. This work done on the charge is called as an __electric potential__.

The Work required to bring the unit positive charge from infinity to any point against electric force is known as electrical potential at that point.

The SI unit is joule/coulomb or volt (V).

**Question 30.**Explain the series connections of resistors and derive the formula of equivalent resistance.

**Answer:**The resistors are connected across two points in the circuit in such a way that the current flowing through each resistor is the same and only one path is available for it to flow, then the resistors are said to be connected in series.

From the figure, if voltage drops across R_{1}, R_{2} & R_{3} are V_{1}, V_{2} & V_{3} respectively.

Moreover, same current I is flowing to all the three resistors.

Using Ohm’s Law

R_{1} voltage drops across V_{1} = IR_{1}

R_{2} voltage drops across V_{2} = IR_{2}

R_{3} voltage drops across V_{3} = IR_{3}

From above three equations

IR = IR_{1} + IR_{2} + IR_{3}

R = R_{1} + R_{2} + R_{3}

**Question 31.**Explain the parallel connection of resistance and drive the formula of equivalent resistance.

**Answer:**When more than one resistances are connected across two points in the circuit such that more than one paths are available for the current to flow and voltage drops across two ends of each resistor are same, then the resistors are said to be connected in parallel between these two points.

From the figure above, suppose the current flowing through resistors R_{1}, R_{2} & R_{3} are I_{1,} I_{2} & I_{3} respectively.

Hence, I = I_{1} + I_{2} + I_{3}

Using Ohm’s Law,

And

From the equations we get,

**Question 32.**Explain electrical energy and drive its formula.

**Answer:**Electrical energy is the energy newly derived from electric potential energy or kinetic energy.

Suppose the electric current is flowing through some resistor (R). To flow this current continuously the battery has to provide energy to every electric charge. Now, the work required to keep the charge Q in motion by the battery of voltage of V is

W = VQ

From the definition of electric current,

Q = It

.: W = VIt

According to Ohm’s Law, V = IR

W = (IR)(I)(t)

The above equation is called __Joule’s Law__.

**Question 33.**Draw the figure of voltaic cell and explain its construction. Explain flow of current in conductor through this cell.

**Answer:**A voltaic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy.

As shown in figure, take solution of dilute sulphuric acid (H_{2}SO_{4}) in a beaker. Dip one copper plate and another zinc plate in the solution in such a way that they do not touch each other. These two plates get electrically charged due to the process between these two plates and the solution. The positive charge at copper plate and negative charge at zinc plate get deposited. Thus, electric potential difference is produced between two plates. Positive charge plate is called positive pole of battery or __anode__ and the negatively charged plate is called negative pole of battery or __cathode__.

Such a simple battery was invented by Italian Scientist __Alexandro Volte__ (1745-1827). Therefore, it is called __Volta’s Cell__.

The electrons flow from cathode towards anode.

**Question 34.**What is electrolyte? Describe the experiment showing flow of current in electrolyte.

**Answer:**An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons

Setting up the experiment as shown in the above figure. When we switch ON the circuit we observe that the bulb does not glow.

On adding some salt in the distilled water, we observe that the bulb has started glowing.

**Question 35.**Write Ohm’s law. Describe the experiment showing Ohm’s law and write its conclusions.

**Answer:**•In the definite physical situation, the electric current flowing through the conductor is directly proportional to the potential difference applied across it is known as __Ohm’s Law__.

•To verify Ohm’s Law experimentally we set up the following circuit

In the following circuit, we have taken 0.5 meter long nichrome wire, four to five battery of 1.5V each, Ammeter and key.

•Now, when the key is ON, the current will flow through the wire. Measure the current in ammeter and potential difference across the two ends using voltmeter and note In the following table

•After this, plot the V vs I on a graph paper, we will observe something like this

•We will observe the following points

1. The electric current in the conductor increases in same proportion with increase in voltage.

2. I-V is a straight line

3. The ratio of V and I remains constant every time.

**Question 36.**What is electroplating? Explain it with example.

**Answer:**Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.

To understand experimentally, let’s take a solution of copper sulphate in a beaker. In this solution, the iron spoon which is to be electroplated and a copper plate are taken as electrodes and are connected with battery and key as shown in the figure below.

On passing the current, the CuSO_{4} which electrolyte in the above case is decomposed into Cu^{2 +} and SO_{4}^{2-}. As Cu^{2 +} is positively charged, so it moves towards negative terminal i.e. Metal spoon and deposits on iron spoon. Thus, on iron spoon the plating.

**Question 37.**If 400 mA current flows through the bulb for 1 minute, how many electrons will pass through it?

**Answer:**__Given__

Current (I) = 400mA = 0.4A

Time (t) = 1min = 60sec

__Formula__

I = current

Q = charge

T = time

Q = I x t

Q = 0.4A x 60 sec

Q = 24 C

Since 1 coulomb contains 0.625 x 10^{19} electrons

Hence 24 C contains 24 x 0.625 x 10^{19} electrons

= 15 x 10^{19} electrons

**Question 38.**The 1800 C electric charge is passing through an electric bulb in one hour. How much current will pass through an electric bulb?

**Answer:**__Given__

Charge (Q) = 1800C

Time (t) = 1 hour = 3600 sec

__Formula__

I = current

Q = charge

T = time

__Calculation__

Current = 0.5A

**Question 39.**The three resistance of resistance 5 Ω, 10 Ω and 30 Ω are connected with a 12 V battery in parallel. Determine (a) total current in the circuit (b) equivalent circuit resistance.

**Answer:**__Given__

Battery = 12V

Resistance (parallel) = 5 Ω, 10 Ω and 30 Ω

__Formula used__

Parallel Resistance formula

Ohm’s Law

V = IR

V = voltage

I = current

R = resistance

__Calculation__

To solve part (a) we first have to solve part (b)

(b) Equivalent resistance

Hence, R = 3 Ω

(a) Total current

I = 4 A

**Question 40.**As shown in the figure the resistance are connected with a 12 V battery. Determine (a) Equivalent circuit resistance (b) Current flowing through the circuit.

**Answer:**1. Equivalent Resistance

__Formula used__

Parallel Resistance formula

Series resistance formula

R_{a} = 8Ω

R_{b} = 10Ω

Since R_{a} & R_{b} are in series, so total resistance is

R_{Total} = R_{a} + R_{b}

R_{Total} = 18Ω

2. Total current

Ohm’s Law

V = voltage

I = current

R = resistance

I = 0.66 A

**Question 41.**Find the electric current in the following circuit:

**Answer:**(a) First, we will find equivalent resistance.

__Formula used__

Parallel Resistance formula

Series resistance formula

The highlighted (yellow colour) resistance are in __series with each other__ and is in __parallel with the other one__.

R_{a} = 30Ω + 30Ω

R_{a} = 60Ω

Total resistance is 20Ω

(b) Total current

__Formula used__

Ohm’s Law

V = voltage

I = current

R = resistance

2V = 20Ω x I

I = 0.1A

**Question 42.**Determine the equivalent resistance between points X and Y in the following circuit.

**Answer:**__Formula used__

Parallel Resistance formula

Series resistance formula

The two resistors highlighted with yellow are in series to each other & both of them are parallel to the 10 Ω resistor.

Equivalent resistance = 5Ω

These 3 resistances are in series.

Hence, total resistance is 15 Ω

**Question 43.**Two lamps of 100 W and 60 W are joined in parallel with 220 V lines. How much current will flow through the circuit?

**Answer:**__Given__

Lamp 1 = 100W

Lamp 2 = 60W

Voltage (V) = 220V

__Formula Used__

Ohm’s Law

V = voltage

I = Current

R = resistance

Power Formula

P = power

V = voltage

R = resistance

Parallel Resistance formula

Resistance of lamp 1

R = 484Ω

Resistance of lamp 2

R = 806.7Ω

Since, both the lamps are joined in parallel; Hence total resistance will be

R = 302.5Ω

Using Ohm’s Law

Total current = 0.73 A

**Question 44.**An electric heater consumes 4.4 kW power when connected with a 220 V lines voltage then,

i. Calculate the current passing through the heater.

ii. Calculate resistance of a heater.

iii. Calculate the energy consumed in 2 hours.

**Answer:**i. Current passing

__Formula used__

Power formula è P = VI

P = power

V = Voltage

I = Current

I = 20 A

ii. Resistance of heater

__Formula used__

Power Formula

P = power

V = voltage

R = resistance

R = 11Ω

iii. Energy consumed in 2 hrs

The power is 4.4 kW; It means that 4400 joules is consumed in 1 sec

In 2 hrs è 3600 x 2 secs

The energy consumed will be

= 4400 x 3600 x 2

= 3.168 x 10^{7} joules

**Question 1.**

The SI unit of electric charge is......

A. ampere

B. volt

C. watt

D. coulomb

**Answer:**

In SI unit system, charge is measured in Coulomb(C)

Charge on electron = -1.6 × 10^{-19}C

**Question 2.**

What number of electrons will be there in 1.6 C charge?

A. 10^{17}

B. 10^{18}

C. 10^{19}

D. 10^{20}

**Answer:**

As 1C = Electrons

**Question 3.**

1μA = --------- mA.

A. 10^{-16}

B. 10^{-3}

C. 10^{3}

D. 10^{6}

**Answer:**

μA = 10^{-6}A

mA = 10^{-3}A

**Question 4.**

Which of the following materials has more number of free electrons?

A. Copper

B. Glass

C. Rubber

D. Iron

**Answer:**

As metals has most number of free electrons and from the choice above copper and iron are metals.

But when we know that more the current flowing in a conductor more are the free electrons. So, copper being a very good conductor has more number of free electrons.

**Question 5.**

According to Ohm’s law,

A. The resistance increases with the increase in current.

B. The resistance increases with the increase in voltage.

C. The current increases with the increases in voltage.

D. The resistance and current both increase with the increase in voltage.

**Answer:**

The Ohm’s Law state that, the potential difference (voltage) across an ideal conductor is proportional to the current through it. The constant of proportionality is called the "resistance", R. Ohm's Law is given by: V = I R where V is the potential difference between two points which include a resistance R.

**Question 6.**

The formula for an electric current is -----.

A. I = Qt

B. I =

C. I =

D. I = Wt

**Answer:**

Electric current means rate of flow of an electric charge.

**Question 7.**

The amount of 2 A electric current is passed for 1 minute through one conducting wire. How much total electric charge will pass through this wire?

A. 2 C

B. 30 C

C. 60 C

D. 120 C

**Answer:**

1 minute = 60 sec.

I = & I = 2A.

2 = . So, Q = 120C

**Question 8.**

In an electrical appliance, the electric current of 4.8 A is passed, then the number of electrons passing through it in one second will be ------------

A. 0.33 x 10^{19}

B. 3.3 x 10^{19}

C. 3 x 10^{19}

D. 4.8 x 10^{19}

**Answer:**

Given I = 4.8 T = 1sec

Using I = we get Q = 4.8C

Since 1C = electrons

So, 4.8C = = 3 x 10^{19} electrons

**Question 9.**

Which of the following formula represents the voltage?

A.

B.

C. Work X electric charge

D. Work x electric charge x time

**Answer:**

Voltage is defined as Work done per unit charge.

V =

Charge = I x T

**Question 10.**

The unit of electric potential difference is ---------

A. J

B. J/C

C. 5 V

D. 45 V

**Answer:**

Voltage is defined as Work Done per unit charge.

V =

**Question 11.**

If the work is to be done to take 3C electric charge from one point to another is 15 J, what will be the potential difference between these two points?

(A) 3 V

(B) 15 V

(C) 5 V

(D) 45 V

**Answer:**

We know that potential difference b/w any two points is work done to carry charge from one point to another. So,

**Question 12.**

The resistance of one conducting wire is 10 Ω. How much electric current will flow by connecting it with a batter of 1.5 V?

A. 0.15 mA

B. 1.5 mA

C. 15 mA

D. 150 mA

**Answer:**

V = I x R

V = 1.5V & R = 10 Ω

Hence 1.5V = 10 Ω x I

I = 150 mA

**Question 13.**

On which factors does the resistivity of conducting wire depend?

A. Length of wire

B. Area of cross-section of wire

C. Volume of wire

D. Material of wire

**Answer:**

Resistivity depends only on material of wire.

**Question 14.**

If the five equal pieces of a resistance wire having 5 resistance each is connected in parallel, then their equivalent resistance will be -----

A. 1/5

B. 1

C. 5

D. 25

**Answer:**

When resistance is connected in parallel we use the following formula

**Question 15.**

The unit of resistivity of the material is –

A.

B. m

C. /m

D. m/

**Answer:**

R(Ω) = ρ x

**Question 16.**

What will be the resistance between points A and B of the following electric circuit?

A. 1

B.2

C. 5

D. 10

**Answer:**

Since all the resistance are in series, so total resistance will be sum of all the resistance.

**Question 17.**

What will be the equivalent resistance between points A and B of the following electric circuit?

A. 4

B. 8

C.2

D 16

**Answer:**

The two 4Ω resistance are in series & are in parallel to 8Ω resistance.

R1 = 8Ω & R2 = 8Ω

**Question 18.**

The equivalent resistance between points A and B in the following electric circuit is. ---.

A.2.5

B.5

C. 12.5

D. 20

**Answer:**

The two 5Ω resistors are in parallel which is results in 2.5Ω in series with the other two 5Ω resistors.

Parallel

**Question 19.**

Which physical quantity has a unit of kWh?

A. Work

B. Electric power

C. Electric current

D. Electric potential.

**Answer:**

It is called kilowatt hour and is a unit for energy and is especially used in electricity bills.

**Question 20.**

1kWh = --------joule

A. 3.6 x 10^{6}

B. 3.6 x 10^{3}

C. 3.6 x 10^{-6}

D. 3.6 x 10^{-3}

**Answer:**

1 kilowatt hour

1 hour = 3600 seconds

1killo = 1000

1 kilowatt hour = 3600000 = A. 3.6 x 10^{6}

**Question 21.**

An electric heater consumes 1.1 kW power when 220 V voltage applied to it. How much current will be flowing through it?

A. 1.1 A

B. 2.2 A

C. 4 A

D. 5 A

**Answer:**

Power = Voltage x Current; Power = 1.1kW = 1100W

Voltage = 220 V

Hence, Current

**Question 22.**

What makes the electric current flow through electric solution?

A. Only free electrons

B. Only positive ions.

C. Only negative ions

D. Positive and negative ions.

**Answer:**

The solution that conducts electricity are called “electrolytes”. In electrolytes, the electric current flows due to both positive and negative ions.

**Question 23.**

The distilled water acts as ----- for the electricity.

A. Conductor

B. Insulator

C. Semiconductor

D. None.

**Answer:**

In distilled water there is no free positive or negative ions hence it acts as an insulator.

**Question 24.**

What is an electric charge? Give its types and write is unit.

**Answer:**

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charges are of two types: Positive electric charge (proton) & negative electric charge (electron). Electric charge is an intrinsic (independent) property of electron and proton like mass.

The SI unit of electric charge is Coulomb.

**Question 25.**

What is a free electron? Explain conducting and non-conducting materials in terms of it.

**Answer:**

In atoms, electrons move around the nucleus where protons remain bound. In some material like metals, under normal circumstances, the attractive force between the valence electrons (outermost ones) and nucleus is comparatively very small.

During the formation of metallic materials, these electrons get separated from their parent atom and move in a random manner. Such electrons are known as Free electrons.

These free electrons are responsible for their electricity conducting property.

**Question 26.**

Give the definition of an electric current and define its unit.

**Answer:**

The net quantity of an electric charge flowing through any cross-section of conductor is defined as electric current.

Thus,

The SI unit of current is Ampere (A).

**Question 27.**

Give advantages of series and parallel connection of resistors.

**Answer:**

The total resistance of the circuit increases by connecting the resistors in series hence, the current decreases. Thus, to control the current in the circuit, series connection of resistors is useful. Moreover, the fuse is always connected in series with the mains. Therefore, whenever there is short circuit in any electrical appliance, the fuse wire melts and stops electric current. As a result, damage to electrical appliance can be prevented.

Whereas, the advantage of parallel connection is that when we connect three bulbs in parallel all will get equal voltage and therefore will give equal amount of light irrespective of each other. Secondly, if any appliance is affected/fused, it will not affect the other appliance. When we need more current we use parallel connection as resistance gets decreased resulting in more amount of current.

**Question 28.**

Write Faraday’s laws of electrolysis.

**Answer:**

On passing the electric current through electrolytic solution, negative charge moves towards positive terminal and positive ions towards negative terminal. This process of separating the ions is called __electrolysis__.

__Faraday’s First Law__ – The mass of substance (metal) deposited at cathode on passing electric current through electrolytic solution is proportional to charge passing through it, M ∝ Q

__Faraday’s Second Law__ – For a given amount of current passed, the masses of different elements deposited on cathode is proportional to their chemical equivalent (e).

**Question 29.**

What is an electric potential? Give the definition and unit of electric potential.

**Answer:**

On bringing some electric charge near any other charge, an attractive or repulsive force exerts on it. Thus, the work is to be done against this force keeping a charge in equilibrium and to move another near or far from it. This work is stored in the form of potential energy. This work done on the charge is called as an __electric potential__.

The Work required to bring the unit positive charge from infinity to any point against electric force is known as electrical potential at that point.

The SI unit is joule/coulomb or volt (V).

**Question 30.**

Explain the series connections of resistors and derive the formula of equivalent resistance.

**Answer:**

The resistors are connected across two points in the circuit in such a way that the current flowing through each resistor is the same and only one path is available for it to flow, then the resistors are said to be connected in series.

From the figure, if voltage drops across R_{1}, R_{2} & R_{3} are V_{1}, V_{2} & V_{3} respectively.

Moreover, same current I is flowing to all the three resistors.

Using Ohm’s Law

R_{1} voltage drops across V_{1} = IR_{1}

R_{2} voltage drops across V_{2} = IR_{2}

R_{3} voltage drops across V_{3} = IR_{3}

From above three equations

IR = IR_{1} + IR_{2} + IR_{3}

R = R_{1} + R_{2} + R_{3}

**Question 31.**

Explain the parallel connection of resistance and drive the formula of equivalent resistance.

**Answer:**

When more than one resistances are connected across two points in the circuit such that more than one paths are available for the current to flow and voltage drops across two ends of each resistor are same, then the resistors are said to be connected in parallel between these two points.

From the figure above, suppose the current flowing through resistors R_{1}, R_{2} & R_{3} are I_{1,} I_{2} & I_{3} respectively.

Hence, I = I_{1} + I_{2} + I_{3}

Using Ohm’s Law,

And

From the equations we get,

**Question 32.**

Explain electrical energy and drive its formula.

**Answer:**

Electrical energy is the energy newly derived from electric potential energy or kinetic energy.

Suppose the electric current is flowing through some resistor (R). To flow this current continuously the battery has to provide energy to every electric charge. Now, the work required to keep the charge Q in motion by the battery of voltage of V is

W = VQ

From the definition of electric current,

Q = It

.: W = VIt

According to Ohm’s Law, V = IR

W = (IR)(I)(t)

The above equation is called __Joule’s Law__.

**Question 33.**

Draw the figure of voltaic cell and explain its construction. Explain flow of current in conductor through this cell.

**Answer:**

A voltaic cell is an electrochemical cell that uses a chemical reaction to produce electrical energy.

As shown in figure, take solution of dilute sulphuric acid (H_{2}SO_{4}) in a beaker. Dip one copper plate and another zinc plate in the solution in such a way that they do not touch each other. These two plates get electrically charged due to the process between these two plates and the solution. The positive charge at copper plate and negative charge at zinc plate get deposited. Thus, electric potential difference is produced between two plates. Positive charge plate is called positive pole of battery or __anode__ and the negatively charged plate is called negative pole of battery or __cathode__.

Such a simple battery was invented by Italian Scientist __Alexandro Volte__ (1745-1827). Therefore, it is called __Volta’s Cell__.

The electrons flow from cathode towards anode.

**Question 34.**

What is electrolyte? Describe the experiment showing flow of current in electrolyte.

**Answer:**

An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of electrons, while the anions are drawn to the electrode that has a deficit of electrons

Setting up the experiment as shown in the above figure. When we switch ON the circuit we observe that the bulb does not glow.

On adding some salt in the distilled water, we observe that the bulb has started glowing.

**Question 35.**

Write Ohm’s law. Describe the experiment showing Ohm’s law and write its conclusions.

**Answer:**

•In the definite physical situation, the electric current flowing through the conductor is directly proportional to the potential difference applied across it is known as __Ohm’s Law__.

•To verify Ohm’s Law experimentally we set up the following circuit

In the following circuit, we have taken 0.5 meter long nichrome wire, four to five battery of 1.5V each, Ammeter and key.

•Now, when the key is ON, the current will flow through the wire. Measure the current in ammeter and potential difference across the two ends using voltmeter and note In the following table

•After this, plot the V vs I on a graph paper, we will observe something like this

•We will observe the following points

1. The electric current in the conductor increases in same proportion with increase in voltage.

2. I-V is a straight line

3. The ratio of V and I remains constant every time.

**Question 36.**

What is electroplating? Explain it with example.

**Answer:**

Electroplating is a process that uses an electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.

To understand experimentally, let’s take a solution of copper sulphate in a beaker. In this solution, the iron spoon which is to be electroplated and a copper plate are taken as electrodes and are connected with battery and key as shown in the figure below.

On passing the current, the CuSO_{4} which electrolyte in the above case is decomposed into Cu^{2 +} and SO_{4}^{2-}. As Cu^{2 +} is positively charged, so it moves towards negative terminal i.e. Metal spoon and deposits on iron spoon. Thus, on iron spoon the plating.

**Question 37.**

If 400 mA current flows through the bulb for 1 minute, how many electrons will pass through it?

**Answer:**

__Given__

Current (I) = 400mA = 0.4A

Time (t) = 1min = 60sec

__Formula__

I = current

Q = charge

T = time

Q = I x t

Q = 0.4A x 60 sec

Q = 24 C

Since 1 coulomb contains 0.625 x 10^{19} electrons

Hence 24 C contains 24 x 0.625 x 10^{19} electrons

= 15 x 10^{19} electrons

**Question 38.**

The 1800 C electric charge is passing through an electric bulb in one hour. How much current will pass through an electric bulb?

**Answer:**

__Given__

Charge (Q) = 1800C

Time (t) = 1 hour = 3600 sec

__Formula__

I = current

Q = charge

T = time

__Calculation__

Current = 0.5A

**Question 39.**

The three resistance of resistance 5 Ω, 10 Ω and 30 Ω are connected with a 12 V battery in parallel. Determine (a) total current in the circuit (b) equivalent circuit resistance.

**Answer:**

__Given__

Battery = 12V

Resistance (parallel) = 5 Ω, 10 Ω and 30 Ω

__Formula used__

Parallel Resistance formula

Ohm’s Law

V = IR

V = voltage

I = current

R = resistance

__Calculation__

To solve part (a) we first have to solve part (b)

(b) Equivalent resistance

Hence, R = 3 Ω

(a) Total current

I = 4 A

**Question 40.**

As shown in the figure the resistance are connected with a 12 V battery. Determine (a) Equivalent circuit resistance (b) Current flowing through the circuit.

**Answer:**

1. Equivalent Resistance

__Formula used__

Parallel Resistance formula

Series resistance formula

R_{a} = 8Ω

R_{b} = 10Ω

Since R_{a} & R_{b} are in series, so total resistance is

R_{Total} = R_{a} + R_{b}

R_{Total} = 18Ω

2. Total current

Ohm’s Law

V = voltage

I = current

R = resistance

I = 0.66 A

**Question 41.**

Find the electric current in the following circuit:

**Answer:**

(a) First, we will find equivalent resistance.

__Formula used__

Parallel Resistance formula

Series resistance formula

The highlighted (yellow colour) resistance are in __series with each other__ and is in __parallel with the other one__.

R_{a} = 30Ω + 30Ω

R_{a} = 60Ω

Total resistance is 20Ω

(b) Total current

__Formula used__

Ohm’s Law

V = voltage

I = current

R = resistance

2V = 20Ω x I

I = 0.1A

**Question 42.**

Determine the equivalent resistance between points X and Y in the following circuit.

**Answer:**

__Formula used__

Parallel Resistance formula

Series resistance formula

The two resistors highlighted with yellow are in series to each other & both of them are parallel to the 10 Ω resistor.

Equivalent resistance = 5Ω

These 3 resistances are in series.

Hence, total resistance is 15 Ω

**Question 43.**

Two lamps of 100 W and 60 W are joined in parallel with 220 V lines. How much current will flow through the circuit?

**Answer:**

__Given__

Lamp 1 = 100W

Lamp 2 = 60W

Voltage (V) = 220V

__Formula Used__

Ohm’s Law

V = voltage

I = Current

R = resistance

Power Formula

P = power

V = voltage

R = resistance

Parallel Resistance formula

Resistance of lamp 1

R = 484Ω

Resistance of lamp 2

R = 806.7Ω

Since, both the lamps are joined in parallel; Hence total resistance will be

R = 302.5Ω

Using Ohm’s Law

Total current = 0.73 A

**Question 44.**

An electric heater consumes 4.4 kW power when connected with a 220 V lines voltage then,

i. Calculate the current passing through the heater.

ii. Calculate resistance of a heater.

iii. Calculate the energy consumed in 2 hours.

**Answer:**

i. Current passing

__Formula used__

Power formula è P = VI

P = power

V = Voltage

I = Current

I = 20 A

ii. Resistance of heater

__Formula used__

Power Formula

P = power

V = voltage

R = resistance

R = 11Ω

iii. Energy consumed in 2 hrs

The power is 4.4 kW; It means that 4400 joules is consumed in 1 sec

In 2 hrs è 3600 x 2 secs

The energy consumed will be

= 4400 x 3600 x 2

= 3.168 x 10^{7} joules