The hot resistance of the bulb's filament is higher than its cold resistance because the temperature co-efficient of the filament is___________________?
Correct answer: C. positive
- A. zero
- B. negative
- C. positive
- D. about 2 ohms per degree
Explanation
The filament is made of a metal with a positive temperature coefficient, so its resistance rises as it becomes hot. This is why the operating or hot resistance is much greater than the cold resistance.
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