Ohm's Law — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Ohm's Law MCQs with step-by-step solutions (7 questions). Part of Electricity & Magnetism. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Ohm's Law · medium · theory
Ohm's law states that, at constant temperature, the current through a conductor is:
A. independent of the potential difference
B. inversely proportional to the potential difference
C. proportional to the square of the voltage
D. directly proportional to the potential difference across it ✓ Correct
Solution: $V = IR$, so $I \propto V$ at constant temperature and resistance.
Q2 — Ohm's Law · medium · numerical
A potential difference of 12 V is applied across a 4 Ω resistor. The current through it is:
A. 48 A
B. 0.33 A
C. 3 A ✓ Correct
D. 16 A
Solution: $I = \dfrac{V}{R} = \dfrac{12}{4} = 3$ A.
Q3 — Ohm's Law · medium · numerical
A current of 2 A flows through a resistor when 10 V is applied across it. Its resistance is:
A. 5 Ω ✓ Correct
B. 12 Ω
C. 0.2 Ω
D. 20 Ω
Solution: $R = \dfrac{V}{I} = \dfrac{10}{2} = 5$ Ω.
Q4 — Ohm's Law · hard · numerical
A current of 0.5 A flows through a 20 Ω resistor. The potential difference across it is:
A. 10 V ✓ Correct
B. 20.5 V
C. 0.025 V
D. 40 V
Solution: $V = IR = 0.5 \times 20 = 10$ V.
Q5 — Ohm's Law · hard · theory
On a graph of potential difference (V) against current (I) for an ohmic conductor, the slope of the straight line gives the:
A. current
B. resistance ✓ Correct
C. charge
D. power
Solution: Since $V = IR$, the V–I graph is a straight line whose slope equals the resistance R.
Q6 — Ohm's Law · medium · numerical
A resistor carries a current of 0.5 A when a potential difference of 6 V is applied across it. What is its resistance?
A. 0.083 ohm
B. 3 ohm
C. 6.5 ohm
D. 12 ohm ✓ Correct
Solution: R = V/I = 6 V ÷ 0.5 A = 12 ohm.
Q7 — Ohm's Law · hard · numerical
The voltage across a fixed resistor is increased from 4 V to 10 V. If the original current was 0.8 A, what is the new current?
A. 1.2 A
B. 2.5 A
C. 0.32 A
D. 2 A ✓ Correct
Solution: The resistance is fixed: R = 4/0.8 = 5 ohm. New current I = V/R = 10/5 = 2 A.