Ohm's Law MCQ

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Ohm’s law MCQ is covered in this article with a detailed explanation of the answers. Ohm’s Law Multiple Choice Questions and answers (MCQs) cover important questions related to Ohm’s Law statement and limitations of the law.

Ohm’s Law gives the relation between the voltage, current, and resistance. The law states that the current I, flowing through a conductor is directly proportional to the potential difference, V, across the end of the conductor. Hence when the physical conditio temperatureprature of the conductor is constant,

Voltage (V) = Current (I) X Resistance (R)

The limitations of Ohm's Law are:

Not applicable to unilateral networks as current is allowed to flow unidirectionally.
Not applicable to non-linear elements of a circuit like a thyristor as the resistance changes for different voltage and current values.
Voltage and current are dependent on the sign of voltage. Eg. diodes

Ohms Law Explained

Ohms law video

Check Out: NCERT Solutions for Class 12 Physics Chapter 3: Current Electricity

Ohm’s Law MCQ and Answers

Ques 1: Ohm’s law holds for

Metallic conductors at low-temperature
For electrolytes, when current passes through them
Metallic conductors at high-temperature
For diode when the current flow

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Ans: The correct option is A. Metallic conductors at low-temperature

Explanation: Metallic conductors at constant temperature and zero magnetic fields have their current proportional to the voltage. However, the current is inversely proportional to the conductor’s resistance. This applies to the majority of metallic substances. But, metals like tungsten used in light bulb filaments have their resistances vary with the temperature of the filament.

Ques 2: Select the correct form of Ohm’s Law:

V ∝ I
V = IR
I = VR
Both A and B

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Ans: The correct option is D. Both A and B

Explanation: As per Ohm’s Law the voltage across an electrical circuit is directly proportional to the current flowing through it. Hence the V/I ratio is a constant known as the electrical resistance given by R. Mathematically,

V ∝ I,

Therefore Ohm’s law formula is V= IR

Ques 3: International ohm is?

Resistance to a column of mercury
Resistance for a unit length of wire
Resistance to a cube of copper
Resistance to a cube of carbon

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Ans: The correct option is A. Resistance for a column of mercury

Explanation: A unit of resistance is defined to be equivalent to a column of mercury measured across a uniform cross-section with a length of 160.3 cm, the mass of 14.4521 g at the temperature of melting ice. Resistance of a column of mercury = 1.00049 ohms.

Ques 4: What happens to the resistance of the carbon filament lamp as the voltage is increased?

Remains the same
Decreases
Increases
None of the above

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Ans: The correct option is B. Decreases

Explanation: In carbon filament lamps, the resistance is low for low potential differences. This increases as the voltage increases and causes the temperature of the filament to rise.

Do Check Out:

Important Topics from Current Electricity
Electric Charge	Cells in Series & Parallel	Resistor Applications
Carbon Resistor	Internal Resistance	Potentiometer
Voltage Divider Formula	Network Analysis	Resistance and Length Formula
Static Electricity	Power and Resistance	Current Density Formula
Gauss Law Applications	Transistors	Gauss’s Law
Wheatstone Bridge	Kirchoff’s Rules	Kirchoff’s Rules
Ampere	Resistivity	Insulators

Ques 5: If two incandescent light bulbs have ratings of 40 and 60 W each and are connected in series across the mains, then?

The 40 W bulb glows brighter
The bulbs together consume 100 W
The 60 W bulb glows brighter
The bulbs together consume 50 W

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Ans: The correct option is A. The 40 W bulb glows brighter

Explanation: The brightness of the bulb will be directly proportional to the power consumed. Hence, the resistance of the 40 W bulb will be higher making it glow brighter when connected in parallel.

Ques 6: If a potential difference of 10 V is applied across a conductor with the resistance of 2.5 ohms, determine the current value.

2 amperes
6 amperes
4 amperes
10 amperes

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Ans: The correct option is C. 4 Amperes

Explanation: From Ohm’s Law, V=IR

Here V= 10 V, R = 2.5 Ω

Thus substituting we get,

10= 2.5I

I= 10/2.5

=4 Amperes

Ques 7: The resistance of a conductor is 50 Ω and 5A current passes through it. Determine the potential difference.

250 V
150 V
50 V
15 V

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Ans: The correct option is A. 250 V

Explanation: From Ohm’s Law, V=IR

R= 50 Ω, I = 5A.

Substituting we get,

V= 50 X 5

= 250 V

Ques 8: A series circuit has a current of 5A. The current drop is 4A when 2Ω resistance is inserted. Determine the original resistance.

8
10
1.25
20

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Ans: The correct option is A. 8

Explanation: From Ohm’s Law, V=IR

Let the current in the first case be = I₁= 5A

Resistance R₁ in the first case= R

The current in the second case= I₂ = 4A

Resistance R₂ in the second case = R+2R

ΔV in the first case = V= I₁R₁= 5R — (1)

ΔV in second case= V= I₂R₂ = 4(R+2) — (2)

Equating (1) and (2) we get,

5R = 4(R+2)

⇒ 5R = 4R + 8

⇒ R = 8 Ω

Ques 9: What is the charge per unit area per unit second in a current called?

Ohm’s Law
E.M.F.
Current Density
Potential Difference

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Ans: The correct option is C. Current Density

Explanation: Current density is defined as the electric charge flowing per unit time through a unit area of a conductor. Mathematically it is given by,

J= i/A

Where J is the current density

The cross-sectional area

I am the electric charge

Ques 10: The V-I plot for Ohmic devices is:

Bi-linear
Linear
Parabolic
Non-linear

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Ans: The correct option is B. Linear

Explanation: The following plots show the V-I relation for Ohmic and Non-Ohmic Devices.

Ohmic vs Non-Ohmic Devices

From the plot, the V-I graph for Ohmic Devices is Linear.

Ohm’s Law MCQ can be studied along with the important questions of Ohm’s Law for a better grasp of the topic.

Read More:

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NCERT Solutions for Class 12 Physics	Formulas in Physics	Physics Study Material
Topics for Comparison in Physics	Choice-based questions in physics	Current Electricity Important Questions
Physics Study Notes	Class 12 Physics Book PDF	Class 12 Physics Practicals
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NCERT Solutions for Class 12 English	NCERT Solutions for Class 12 Maths	Class 12 Chemistry Practicals
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Ohm's Law MCQ

Ohms Law Explained

Ohm’s Law MCQ and Answers

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.

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Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

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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.

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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: \( n_i = 1.5 \times 10^{16} \, \text{m}^{-3} \))

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Ohm's Law MCQ

Ohms Law Explained

Ohm’s Law MCQ and Answers

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.

3.Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

4. 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.

5.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: \( n_i = 1.5 \times 10^{16} \, \text{m}^{-3} \))

6.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:

Similar Physics Concepts

Comments

SUBSCRIBE TO OUR NEWS LETTER

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.

3.
Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

4.
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.

5.
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: \( n_i = 1.5 \times 10^{16} \, \text{m}^{-3} \))

6.
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: