A 100 W bulb and a 60 W bulb are designed for the same mains voltage. Compared with the 60 W bulb, the 100 W bulb has
- A. a higher resistance
- B. a lower resistance and draws more current
- C. the same resistance
- D. a lower current
Explanation
At a fixed voltage, power is V squared over R, so a higher power rating means a lower resistance and therefore a larger current. Students often assume more power means more resistance, which is only true when the current rather than the voltage is fixed. Connecting the two bulbs in series reverses their apparent brightness for exactly this reason.