Unit of Voltage MCQs with Solutions

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Voltage is defined as the electric potential between two points in a conductor. The SI unit of voltage is volt. It is represented by the symbol ‘V’. A volt can be expressed as the electric potential in a wire when an electric current of 1 Ampere dissipates power of 1 watt. This can be written as;

V = W/A

In terms of energy, volt can be defined as the potential difference between two points in an electrical circuit that gives 1 Joule of energy per coulomb of charge. This can be expressed as;

V = Potential Energy / Charge

V = J/C

Check Also: NCERT Solutions for Class 12 Physics


MCQs on Unit of Voltage

Ques 1. In the ladder network shown, current through the resistor 3Ω is 0.25 A. The input voltage 'V' is equal to:

In the ladder network shown, current through the resistor 3Ω is 0.25 A.

  1. 10 V
  2. 20 V
  3. 5 V
  4. 15/2 V

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Ans. (b). 20 V

Explanation: Current through the 3Ω resistor is 0.25 A. Total resistance of this branch is 6, same as the parallel branch since both have the same resistance so current will also be the same. 

Total current from 5Ω resistance is 0.25 + 0.25 = 0.5 A

Total resistance of 5Ω branch = 5 + (6 6) / 6 + 6 = 8Ω

If current through resistor 8Ω is 0.5 A, total resistance of that branch is 8.

So, total current from 7Ω resistance is 0.5 + 0.5 = 1 A

Total resistance of the circuit = 7 + (8 8) / (8 + 8) + 9 = 20Ω 

V = IR

V = 1 20

V = 20 Volts

Ques 2. If two bulbs of power 25 W and 100 W respectively each rated at 220 V are connected in series with the supply of 440 V, which bulb will fuse?

  1. 25 W bulb
  2. 40 Watts
  3. Both a and b
  4. None of these

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Ans. (a). 25 W bulb

Explanation: P1 = 25 W ; P2 = 100 W ; V = 220 V and V’ = 440 V

P = V2/R 

R1 = V2/P1

R1 = (220)2/25 = 1600 Ω 

R2 = V2/P2 

R2 = (220)2/100 = 400 Ω

They are connected in series, so effective resistance is;

R1 = R1 / R1 + R2 

R2 = R2 / R1 + R2 

∴ V1 = V’ R1 / R1 + R2

V2 = V’ R2 / R1 + R2

V1 = 440 1600/2000 = 352 V

V2 = 440 440/2000 = 96.8 V

So, Voltage across 25 W is greater than the range specified and thus this bulb will fuse. 

Ques 3. A charge is moved from point A to point B. The work done to move unit charge during this process is called:

  1. Potential at A
  2. Potential at B
  3. Potential Difference between A and B
  4. Current from A to B

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Ans. (c). Potential Difference between A and B

Explanation: The work done per unit charge in moving it from point A to B is called potential difference between A and B. 

Ques 4. The potential difference (VA - VB) between the points A and B in the given figure is: 

The potential difference (VA - VB) between the points A and B

  1. 9 V
  2. - 3 V
  3. 3 V
  4. 6 V

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Ans. (a). 9 V

Explanation: I = 2 A

Using Kirchhoff’s laws, 

VA - I(2) - 3 - I(1) - VB = 0

∴ VA - 2 2 - 3 - 2 1 - VB = 0 

VA - 9 - VB = 0

VA - VB = 9 V

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Ques 5. In the below circuit, the potential difference between A and B is:

In the below circuit, the potential difference between A and B

  1. 20 V
  2. 30 V
  3. 10 V
  4. 40 V

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Ans. (c). 10 V

Explanation: Let q1 and q2 be the charge flowing in the loops I and II respectively. 

Let q1 and q2 be the charge flowing in the loops I and II respectively

Applying Kirchhoff’s rule in loop I;

q1/1 + (q1 + q2 / 3) - 190 = 0

4q1 + q2 = 190 x 3 

Applying Kirchhoff’s rule in loop II;

(q1 + q2 / 3) + q2/3 + q2/1 = 0

q1 = – 5q2 

Now, put this value of q1 in the above equation,

4 (- 5q2) + q2 = 190 x 3

q2 = 30 μC

Thus, potential difference VAB = q2 / 3μF = 30μ C / 3μF 

VAB = 10 V

Ques 6. In the given circuit, the potential difference across 3 F capacitor will be:

In the given circuit, the potential difference across 3 F capacitor

  1. 12 V
  2. 10 V
  3. 6 V
  4. 4 V

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Ans. (b). 10 V

Explanation: The capacitor and battery are in series, so

Veq = 20 - 4 = 16 V

Ceq = 3 x 5 / 5 + 3 = 15/8

q = Ceq Veq = 15/8 x 16 

q = 30

V3 = q/c = 30/3 = 10 V

Ques 7. A current of 2 A flows in an electric circuit as shown in the figure. The potential difference (VR - Vs) in volts (VR and Vs are potentials at R and S respectively) is:

A current of 2 A flows in an electric circuit as shown in the figure

  1. - 4 V
  2. 2 V
  3. 4 V
  4. - 2 V

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Ans. (c). 4 V

Explanation: Current through R = 1 A and through S is also 1 A. 

VR - Vs = (Vp - Vs) - (Vp - VR)

VR - Vs = (7 x 1) - (3 x 1)

VR - Vs = 4 V

Ques 8. In the circuit shown, the internal resistance of the battery is 1.5 Ω and Vp and VQ are potentials at P and Q respectively. What is the potential difference between points P and Q?

In the circuit shown, the internal resistance of the battery is 1.5 Ω and Vp and VQ are potentials at P and Q respectively

  1. Zero
  2. 4 V (Vp > VQ)
  3. 4 V (VQ > Vp
  4. 2.5 V (VQ > Vp)

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Ans. (d). 2.5 V (VQ > VP)

Explanation: Req = 5/2 Ω 

I = 20 / (5/2 + 1.5) = 5 A

Potential difference between X and P 

VX - VP = (5/2) 3 = 7.5 V …..(i)

Potential difference between X and Q

VX - VQ = (5/2) 2 = 5 V …..(ii)

Solving (i) and (ii),

VP - VQ = - 2.5 V

Minus sign indicates that VQ > VP 

Ques 9. The unit of electric potential difference is:

  1. J
  2. J/C
  3. JC
  4. C/J

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Ans. (b). J/C

Explanation: The potential difference is given by;

ΔV = Q/C 

Thus, the unit of electric potential difference is joule per coulomb denoted by J/C.

Ques 10. The potential difference between the points B and A is:

The potential difference between the points B and A

  1. - 9.1 V
  2. 7.9 V
  3. 8.9 V
  4. 9.1 V

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Ans. (b). 7.9 V

Explanation: VB - VA = 5 - 1 9 - 6 - 4 - 29 + 2 - 49 - 39

VB - VA = -1 - 4 + 2 - I (1 + 2 + 4 + 3)

VB - VA = -5 + 2 - I (10)

VB - VA = -7 - 1/10

VB - VA = -7 - 0.9

VB - VA = -7.9 V

|VB - VA| = 7.9 V

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CBSE CLASS XII Related Questions

  • 1.
    A tank is filled with a liquid to a height of \( 12.5 \, \text{m} \). The apparent depth of a needle lying at the bottom of the tank is measured to be \( 9.0 \, \text{m} \). Calculate the speed of light in the liquid.


      • 2.
        Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

          • attract with a force \( \frac{F}{2} \)
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        • 3.
          A long solenoid of length \( L \) and radius \( r_1 \) having \( N_1 \) turns is surrounded symmetrically by a coil of radius \( r_2 \, (r_2>r_1) \) having \( N_2 \) turns (\( N_2 \ll N_1 \)) around its mid-point. Derive an expression for the mutual inductance of solenoid and coil. Is \( M_{12} = M_{21} \) valid in this case?


            • 4.
              Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.


                • 5.
                  Draw the number of scattered particles versus the scattering angle graph for scattering of alpha particles by a thin foil. Write two important conclusions that can be drawn from this plot.


                    • 6.
                      Suppose a pure Si crystal has \( 5 \times 10^{28} \) atoms per \( \text{m}^3 \). It is doped with \( 5 \times 10^{22} \) atoms per \( \text{m}^3 \) of Arsenic. Calculate majority and minority carrier concentration in the doped silicon. (Given: \( n_i = 1.5 \times 10^{16} \, \text{m}^{-3} \))

                        CBSE CLASS XII Previous Year Papers

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