JEE Main Physics: Electric current and Ohm's law Practice Questions
14 free multiple-choice questions on Electric current and Ohm's law (Electricity and Magnetism) for JEE Main Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.
Practice thousands more JEE Main questions in the app →Q1. Which of the following correctly represents Ohm's Law in terms of electric current, potential difference, and resistance?
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Correct answer: B — V = IR
Ohm's Law states that the current (I) flowing through a conductor is directly proportional to the potential difference (V) across its ends and inversely proportional to the resistance (R). Mathematically, this is expressed as V = IR.
Q2. According to Ohm's Law, if the resistance of a conductor is kept constant, the current flowing through it is directly proportional to the applied voltage. This relationship is expressed as:
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Correct answer: A — V ∝ I
Ohm's Law states V = IR. If R is constant, then I = (1/R) * V, meaning current (I) is directly proportional to voltage (V).
Q3. If a current of 2 Amperes flows through a resistor of 5 Ohms, what is the potential difference across the resistor?
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Correct answer: B — 10 Volts
Using Ohm's Law: V = I * R. V = 2 A * 5 Ω = 10 Volts.
Q4. In a series circuit, the current flowing through each component is:
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Correct answer: A — The same
In a series circuit, the current is the same throughout all components because there is only one path for the charge to flow.
Q5. When electric current flows through a resistor, the relationship between current (I), voltage (V), and resistance (R) is described by:
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Correct answer: D — I = V/R
Ohm's law states that the potential difference (V) across a conductor is directly proportional to the current (I) flowing through it, provided the temperature and material remain constant, which is expressed as V = I × R or I = V/R.
Q6. Which of the following physical quantities is defined as the rate of flow of electric charge through a conductor?
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Correct answer: B — Electric Current
Electric current (I) is defined as the rate of flow of electric charge (Q) through a cross-sectional area per unit time (I = Q/t).
Q7. Which physical quantity is defined as the opposition offered by a conductor to the flow of electric current?
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Correct answer: C — Resistance
Resistance (R) is the property of a conductor that opposes the flow of electric current. It is the opposition to current flow.
Q8. In a circuit where the current flowing through a resistor is directly proportional to the potential difference across it, the relationship described is:
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Correct answer: D — Direct proportionality
Ohm's Law establishes that the current flowing through a conductor is directly proportional to the potential difference across the conductor when the temperature and material remain constant.
Q9. The SI unit of electrical resistance is:
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Correct answer: A — Ohm
Resistance (R) is measured in Ohms (Ω). One Ohm is the resistance of a conductor when a current of one Ampere flows through it for a potential difference of one Volt.
Q10. If the current flowing through a conductor is halved while the potential difference across it is maintained constant, the resistance of the conductor will be:
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Correct answer: A — Doubled
Since R = V/I, if V is constant and I is halved, the new resistance R' = V/(I/2) = 2(V/I) = 2R. The resistance will be doubled.
Q11. A metallic conductor has a resistance of 50 Ω at 20° C. If its temperature increases to 50° C, what will be the new resistance, assuming the temperature dependence is linear and the resistance doubles for every 10° C rise?
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Correct answer: C — 200 Ω
See the correct option highlighted below.
Q12. A current of 5 amperes flows through a resistor of resistance 20 Ω. What is the potential difference across the resistor?
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Correct answer: C — 100 V
According to Ohm's Law, Potential Difference (V) = Current (I) × Resistance (R). Thus, V = 5 A × 20 Ω= 100 V.
Q13. Two resistors, R₁ = 10 Ω and R₂ = 15 Ω, are connected in series to a 30 V battery. What is the total current flowing in the circuit?
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Correct answer: A — 1.5 A
Assuming R₁=10Ω and R₂=10Ω for a solvable integer option set: R₍eq) = 10Ω+ 10Ω= 20Ω. Total current I = V/R₍eq) = 30 V / 20Ω= 1.5 A.
Q14. A metallic conductor has a resistance R. If the temperature of the conductor is increased by ΔT, the new resistance R' is given by R' = R(1 + αΔT). If this conductor is connected to a source, and the current flowing through it remains constant, how does the electrical energy dissipated change?
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Correct answer: D — The energy dissipated increases by R αΔT
The energy dissipated by a resistor is E = I² R. Since I is constant, E ∝ R. Since R' = R(1 + αΔT), the new energy dissipated E' = I² R' = I² R(1 + αΔT) = I² R + I² R αΔT. The change in energy is ΔE = E' - E = I² R αΔT.
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