Why could we not use the Wheatstone bridge to measure the re

Why could we not use the Wheatstone bridge to measure the resistance to current flow of an electric heater when it is operating? Why does the procedure in this experiment instruct you to find a null point that is near the center of the slide Wire? What the effect of a change in the ambient temperature on the resistivity of the wire? Give a quantitative answer using the temperature coefficient of resistivity for copper, alpha = 3.82 times l0^-3 degreeC^-1. Compare p at 28 degree C.

Solution

1) When heater is operating , it\'s temperature keeps changing with time and we know that resitance is a function of temperature , hence the reading obtained while operating it will vary depending on surrounding temperature ,hence could not be standardised. Hence it is measured at OFF condition in a wheatstone brigde.

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