Electrical power and I-V characteristics Quiz
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5 questions, one answer each
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1. A heater draws 8.0 A from a 230 V supply. What is its power?
- A. 29 W
- B. 0.035 W
- C. 1.9 kW
- D. 1.8 kW
2. Which statement explains why the resistance of a filament lamp rises as the current increases?
- A. More electrons are released from atoms
- B. The filament gets longer
- C. Metal ions vibrate more, so collisions with conduction electrons are more frequent
- D. Electrons collide with each other more often
3. A 12 Ω resistor and a 4.0 Ω resistor are in series. Which has the greater power?
- A. The 12 Ω resistor, because the same current gives P = I²R
- B. The 4.0 Ω resistor
- C. They dissipate equal power
- D. It cannot be determined
4. What is the p.d. across a reverse-biased silicon diode in series with a resistor and a 6.0 V cell?
- A. 0.7 V
- B. 0 V
- C. 3.0 V
- D. About 6.0 V
5. An NTC thermistor is connected across a fixed p.d. As it warms, what happens to its power?
- A. It decreases as the current falls
- B. It increases because its resistance falls and P = V²/R
- C. It stays constant
- D. It increases because its resistance rises