Medium
A student records the potential difference (V) across a resistor and the current (I) through it:
V (volt): 2, 4, 6, 8
I (ampere): 0.5, 1.0, 1.5, 2.0
Find the resistance of the resistor and the power consumed when V = 8 V.
Explanation
Explanation
Step 1: By Ohm's law, R = V ÷ I. First reading: 2 ÷ 0.5 = 4 Ω.
Step 2: Check other readings: 4 ÷ 1.0 = 4, 6 ÷ 1.5 = 4, 8 ÷ 2.0 = 4. The ratio is constant, so the resistor is ohmic with R = 4 Ω.
Step 3: Power at 8 V: P = V × I = 8 × 2.0 = 16 W.
Step 4: Cross-check with P = V² ÷ R = 64 ÷ 4 = 16 W ✓.
Answer: 4 Ω and 16 W.
PRO TIP
Re-check your working by substituting the answer back into the original question.