Two electric bulbs have 40W and 60W rating at 220V, then the ratio of their resistance will be
Correct answer: A. 3 : 2
- A. 3 : 2
- B. 2 : 3
- C. 3 : 4
- D. 4 : 3
Explanation
The correct answer is 3 : 2. The resistance of an electrical device is calculated using the formula R = V2/P, where R is resistance, V is voltage, and P is power. For the given bulbs:For the 40W bulb, R1 = 2202/40.For the 60W bulb, R2 = 2202/60.Thus, the ratio of their resistances R2/R1 = (2202/60) / (2202/40) = 40/60 = 2/3. Therefore, R1/R2 = 3/2, which simplifies to a resistance ratio of 3 : 2.The other options are incorrect because they do not reflect the inverse relationship between power and resistance at a constant voltage.
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Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.
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