Cells, Emf, and Internal Resistance MCQ

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:

Topic Related Articles
Kirchhoff’s Laws MCQ	Wheatstone Bridge MCQ	Cells in series and parallel MCQ
Kirchhoff’s Laws Important Questions	Wheatstone Bridge Important Questions	Cells in series and parallel Important questions

MCQs on Cells, emf, Internal Resistance

Ques. What is the dimensional formula of emf?

[M¹L²T^-³A^-1]
[M¹L³T^-³A^-1]
[M¹L³T^-³A^-2]
[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?

Distance between electrodes
Temperature of electrolyte
Nature of electrode and electrolyte
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.

2v
3v
5v
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.

10 ohm
11 ohm
12 ohm
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?

Voltmeter
Potentiometer
Multimeter
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?

1v
2v
3v
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:

Related Articles
Circuit Diagram	Resistors in series and parallel	Internal resistance formula
Resistor Colour Codes	Cells in series and parallel	Uses of Resistor
Electromotive Force	Resistance Formula	Electrical Current

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

Voltmeter
Potentiometer
Multimeter
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?

0.8W
0.6W
0.7W
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

Mechanical
Chemical
Solar
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?

E
E/2
2E
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?

Increase internal resistance
Increase voltage output
Increase current capacity
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?

MgO
MgBr
MnO₂
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:

PCMB Guide Articles
NCERT Class 12 PCMB Textbook	Class 12 PCMB Notes	Class 12 Biology Book Pdf
NCERT Solutions for Class 12 Biology	Class 12 PCMB Textbooks	Physics Study Material
Important Physics Derivations	Class 12 Physics Notes	Class 12 English Book Pdf
Important Physics Formulae	Current Electricity Important Questions	NCERT Solutions for Class 12 Chemistry
Comparison Articles in Physics	Class 12 Physics Book Pdf	CBSE Class 12 Physics Practicals
NCERT Solutions for Class 12 Maths	Class 12 Maths Book	Important Physics Constants
SI Units in Physics	Important Physics MCQs	NCERT Solutions for Class 12 Physics

CBSE CLASS XII Related Questions

1.
A current carrying circular loop of area A produces a magnetic field $ B $ at its centre. Show that the magnetic moment of the loop is $ \frac{2BA}{\mu_0} \sqrt{\frac{A}{\pi}} $.
View Solution
2.
The electric field at a point in a region is given by $ \vec{E} = \alpha \frac{\hat{r}}{r^3} $, where $ \alpha $ is a constant and $ r $ is the distance of the point from the origin. The magnitude of potential of the point is:
- $ \frac{\alpha}{r} $
- $ \frac{\alpha r^2}{2} $
- $ \frac{\alpha}{2r^2} $
- $ -\frac{\alpha}{r} $
View Solution
3.
In the circuit, three ideal cells of e.m.f. $ V $, $ V $, and $ 2V $ are connected to a resistor of resistance $ R $, a capacitor of capacitance $ C $, and another resistor of resistance $ 2R $ as shown in the figure. In the steady state, find (i) the potential difference between P and Q, (ii) the potential difference across capacitor C.
View Solution
4.
A system of two conductors is placed in air and they have net charge of $ +80 \, \mu C $ and $ -80 \, \mu C $ which causes a potential difference of 16 V between them.
(1) Find the capacitance of the system.
(2) If the air between the capacitor is replaced by a dielectric medium of dielectric constant 3, what will be the potential difference between the two conductors?
(3) If the charges on two conductors are changed to +160µC and −160µC, will the capacitance of the system change? Give reason for your answer.
View Solution
5.
A rectangular glass slab ABCD (refractive index 1.5) is surrounded by a transparent liquid (refractive index 1.25) as shown in the figure. A ray of light is incident on face AB at an angle $i$ such that it is refracted out grazing the face AD. Find the value of angle $i$.
$A rectangular glass slab ABCD (refractive index 1.5)$
View Solution
6.
Write the mathematical forms of three postulates of Bohr’s theory of the hydrogen atom. Using them prove that, for an electron revolving in the $ n $-th orbit,
(a) the radius of the orbit is proportional to $ n^2 $, and
(b) the total energy of the atom is proportional to $ \frac{1}{n^2} $.
View Solution