discuss the difficulties of testing whether the filament of a light bulb obeys ohms law
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Just make sure the filament is at a constant temperature, which means a constant current. If you measure the resistance with an ohmmeter, the current is very small, so the filament will be cold.
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Just make sure the filament is at a constant temperature, which means a constant current.
If you measure the resistance with an ohmmeter, the current is very small, so the filament will be cold. If you now supply current from a power supply adjusted to the same small current that the ohmmeter used, and then measure the voltage, you will find that ohm’s law applies. But that will not apply at any higher current.
No matter what current you apply to the filament, when you measure the voltage, by definition the resistance will be equal to the measured voltage divided by the measured current. This is exactly how an ohmmeter works.
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