Ohm law states that, at constant temperature, the current through a conductor is
- A.inversely proportional to the potential difference across it
- B.directly proportional to the potential difference across it
- C.independent of the potential difference across it
- D.proportional to the square of the potential difference across it
Correct answer
Explanation
The correct answer is B, directly proportional to the potential difference across it. Ohm found that for a metallic conductor at a steady temperature the ratio of potential difference to current is a constant, the resistance, which is written as V equals I into R, so doubling the voltage doubles the current. Option A is wrong because an inverse relation would mean a larger battery drives less current, the opposite of what is observed. Option C is wrong because current clearly depends on the applied voltage; a conductor carries no current when the potential difference is zero. Option D is wrong because a square law describes power, which equals voltage into current and so varies as the square of the voltage for a fixed resistance, a distinction examiners deliberately test. The condition of constant temperature matters, because resistance rises as a metal grows hotter.
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Practice Questions
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