Cells, Emf, and Internal Resistance MCQ

Collegedunia Team logo

Collegedunia Team

Content Curator

Cells, emf and internal resistance are all components of an electrical circuit. A cell has both emf and internal resistance and thus are interrelated to one another. Cells, emf and Internal resistance topic is part of Class 12 Physics Chapter 3 Current Electricity.

  • Cell: It is the electrical component which supplies electricity to the electric circuit. A cell converts chemical energy into electrical energy. 
  • Emf: Emf or Electromotive force is a force that is developed from the source which is used to drive the charges from one point to another. It is denoted by the symbol ε.
  • Internal Resistance: Every component in an electrical circuit has an internal resistance that is due to the material in which it is made. This resistance reduces the amount of current flowing through the circuit. 

Check Out:


MCQs on Cells, emf, Internal Resistance

Ques. What is the dimensional formula of emf?

  1. [M1L2T-3A-1]
  2. [M1L3T-3A-1]
  3. [M1L3T-3A-2]
  4. [M1L2T2A-2]

Click here for the answer

Ans. a

Explanation: Emf is a potential difference across the ends of the battery when no current is drawn from it. The dimensional formula emf (????) is the same as that of the potential difference.

 

The formula of potential difference is 

V = W/q 

where 

  • q is the charge. 
  • W is the work done
 

Dimensions of work is, [W] = [M1L2T-2]

Dimensions of charge is, [q] = [A1T1]

Therefore, the dimensional formula of emf is

[????]= [V] = [M1L2T-2] / [A1T1]

⇒ [????] = [ML2T-3A-1]

 

The SI unit of emf is Joule/Coulomb or JC-1.

Ques. Which of the following factors does internal resistance not depend upon?

  1. Distance between electrodes
  2. Temperature of electrolyte
  3. Nature of electrode and electrolyte
  4. Area of electrode

Click here for the answer

Ans. b

Explanation: Internal resistance of a cell depends on the distance of electrodes, nature of the material of the electrodes and area of electrodes. But it does not depend on the temperature of the electrolyte in any way.

Ques. A 3A current passes through an electric circuit for 5 minutes and 900 J of work is done. Find the emf.

  1. 2v
  2. 3v
  3. 5v
  4. 1v

Click here for the answer

Ans. d

Explanation: Current = 3A

Time = 5 minutes = 300 sec

Work done = 900J

Power = Work done/time

Power = 900/300 = 3W

Power = emf x current

Emf = Power/ current

Emf = 3/3

Emf = 1V

Ques. The emf of a battery is 6v, current of 0.5A and internal resistance is 1 ohm. If the cell is connected to a resistor, find the resistance.

  1. 10 ohm
  2. 11 ohm
  3. 12 ohm
  4. 13 ohm

Click here for the answer

Ans. b

Explanation: emf = 6v

Current = 0.5A

Internal resistance = 1 ohm

We know that,

I = e/R + r

0.5 = 6/ R + 1

R = 11 ohms

Ques. Which device is suitable to measure emf?

  1. Voltmeter
  2. Potentiometer
  3. Multimeter
  4. Galvanometer

Click here for the answer

Ans.: b

Explanation: Potentiometer is a very sensitive device and can be used to measure accurate emfs. Unlike a voltmeter, a potentiometer does not draw current from the circuit.

Ques. What is the value of internal resistance of an ideal cell?

  1. 1v
  2. 2v
  3. 3v
  4. 0v

Click here for the answer

Ans. d

Explanation: An ideal cell should be such that it should offer no resistance in the electric circuit.

Check Out:

Ques. Which of the following has the highest internal resistance?

  1. Voltmeter
  2. Potentiometer
  3. Multimeter
  4. Galvanometer

Click here for the answer

Ans. a

Explanation: Voltmeter is a device that is used for measuring the potential difference between 2 points in a circuit. In an ideal condition, the voltmeter should not draw any current from the circuit. Therefore it should have the maximum resistance among the given options.

Ques. How much electricity can one solar cell produce?

  1. 0.8W
  2. 0.6W
  3. 0.7W
  4. 0.1W

Click here for the answer

Ans. c

Explanation: A standard solar photovoltaic cell can produce 0.7 Watts of electricity.

Ques. A battery converts ____ energy into electrical energy

  1. Mechanical
  2. Chemical
  3. Solar
  4. Hydro

Click here for the answer

Ans. b

Explanation: A typical battery converts chemical energy into electrical energy by the use of cathode, anode and electrolyte through the process of electrolysis.

Ques. What will be the potential difference if a cell of emf E and internal resistance

r is connected to resistor of resistance r?

  1. E
  2. E/2
  3. 2E
  4. 4E

Click here for the answer

Ans. b

Explanation: We know that, E-V = Ir

By Ohms law,

V = Ir

Substituting V,

E - Ir = Ir

E = 2Ir

I = E/2r

From Ohm’s law,

V = E/2r x r

V = Er/2r

Thus,

V = E/2

Ques 11. What is the purpose of connecting cells in parallel?

  1. Increase internal resistance
  2. Increase voltage output
  3. Increase current capacity
  4. Decrease current capacity

Click here for the answer

Answer: d

Explanation: When cells are connected in parallel, the voltage remains constant, internal resistance decreases and current capacity increases.

Ques. In a dry cell, the cathodic material is usually?

  1. MgO
  2. MgBr
  3. MnO2
  4. ZnO

Click here for the answer

Ans. c

Explanation: In a dry cell, the following are the components.

Anode - Zinc

Cathode - Graphite rod (carbon)

Cathodic material - Manganese oxide and carbon

Read More:

CBSE CLASS XII Related Questions

  • 1.
    If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.


      • 2.
        Two heaters rated as \((P_1,V)\) and \((P_2,V)\) are connected in series across a dc source of \(V/2\) volt. The power consumed by the combination will be –

          • \((P_1+P_2)\)
          • \(\dfrac{P_1+P_2}{2}\)
          • \(\dfrac{P_1P_2}{2(P_1+P_2)}\)
          • \(\dfrac{P_1P_2}{4(P_1+P_2)}\)

        • 3.
          Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

            • (i) and (iii) only
            • (iii) and (iv) only
            • (i), (iii) and (iv) only
            • All of them

          • 4.
            Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.


              • 5.
                If both the number of protons and the neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction? Explain.


                  • 6.
                    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.

                      CBSE CLASS XII Previous Year Papers

                      Comments


                      No Comments To Show