Resistance changes with temperature and light Quiz
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5 questions, one answer each
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1. A copper wire is heated. Which change explains the increase in resistance?
- A. More conduction electrons are released
- B. Ions vibrate more, so collisions with electrons are more frequent
- C. The wire becomes shorter
- D. Electrons collide with each other more often
2. Which statement about an NTC thermistor on heating is correct?
- A. n increases greatly and outweighs the fall in drift velocity
- B. n decreases and v increases
- C. n stays the same and v increases
- D. Lattice vibrations decrease
3. What is the main reason an LDR's resistance falls in bright light?
- A. Light heats the lattice
- B. The LDR becomes shorter
- C. The ions stop vibrating
- D. Photons release more conduction electrons
4. Why does a thermistor's resistance change by a much larger factor than a metal's over the same temperature range?
- A. A metal has more lattice vibrations
- B. The number of carriers in a semiconductor changes by a large factor
- C. A thermistor has a much larger area
- D. A metal has a lower resistance
5. An LDR across a fixed 6.0 V supply carries 0.30 mA in dim light and 15 mA in bright light. Assuming v is unchanged, n has increased by a factor of about:
- A. 5
- B. 15
- C. 500
- D. 50