1. A small light bulb is marked with "2.5V 0.3A". The "0.3A" refers to the bulb's:
- A. Actual current
- B. Rated current
- C. Minimum current
- D. Maximum allowable current
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Measuring Electric Power of Small Light Bulb - Quiz
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A small light bulb is marked with "2.5V 0.3A". The "0.3A" refers to the bulb's:
Measuring Electric Power of Small Light Bulb - Quiz - Quiz Questions
Measure your mastery of rated power, actual power, and the application of the $P=UI$ formula through the following exercises.
2. In the experiment of measuring electric power, when the slider is moved to the left to increase the voltmeter reading, the brightness of the bulb will:
- A. Become brighter
- B. Become dimmer
- C. Remain unchanged
- D. Become brighter then dimmer
3. It is known that the actual voltage across a small light bulb is half of the rated voltage. Ignoring the change in resistance, its actual power is what fraction of the rated power?
- A. 1/2
- B. 1/4
- C. 1/8
- D. Equal
4. At a certain moment in the experiment, the voltmeter reads $3V$ and the ammeter reads $0.4A$. What is the actual power of the small light bulb at this time?
- A. 1.2 W
- B. 7.5 W
- C. 0.75 W
- D. 12 W
5. Why is a small light bulb more likely to burn out when the switch is just closed (cold state) than after emitting light for a while (hot state)?
- A. Cold state resistance is large, current is small
- B. Cold state resistance is small, instantaneous power/current is large
- C. Hot state resistance is small, current is large
- D. Irrelevant to cold or hot
6. Two light bulbs with the same rated voltage are connected in series in a circuit. Which one is brighter?
- A. The one with larger rated power
- B. The one with smaller rated power
- C. Equally bright
- D. Cannot be determined
7. Regarding LED lights and incandescent lights, which of the following statements is correct:
- A. At the same brightness, incandescent lights save more power
- B. At the same power, LED lights are brighter
- C. The light-emitting principle of LED lights is the heating effect of current
- D. The luminous efficiency of incandescent lights is as high as 90%
8. In the experiment, if the ammeter is mistakenly connected in parallel across the bulb, what might happen after closing the switch?
- A. The bulb lights up normally
- B. The bulb does not light up, the ammeter burns out
- C. The voltmeter reading is huge
- D. The bulb is extremely bright
9. If the voltmeter in the circuit is broken, and you are only given a fixed resistor $R_0$ with known resistance and an ammeter, can you measure the rated power of the small light bulb?
- A. Yes
- B. No
- C. Only rated voltage can be measured
- D. Only rated current can be measured
10. True or False: When the actual voltage across the bulb equals the rated voltage, the actual power of the bulb equals the rated power, and the bulb emits light normally.
- True
- False