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A potential difference of 12 V is applied across a resistor and a current of 3 A flows. What is its resistance?
A0.25 ohm
B36 ohm
C9 ohm
D4 ohm
Answer & Solution
Correct answer: D. 4 ohm
1. By Ohm's law, $R = \dfrac{V}{I}$.
2. Substitute $V = 12\,\text{V}$ and $I = 3\,\text{A}$.
3. $R = \dfrac{12}{3} = 4\,\Omega$.
4. Choosing 36 mistakenly multiplies $V\times I$ (that gives power, not resistance).
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 4 Electricity "Electricity", p.62_
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