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  4. In a potentiometer, the null point is received at 7th wire. If now we have to change the null point at the 9th wire, what should we do?

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Q. In a potentiometer, the null point is received at $7th$ wire. If now we have to change the null point at the $9th$ wire, what should we do?

Delhi UMET/DPMTDelhi UMET/DPMT 2008Current Electricity

Solution:

The working of potentiometer is based on the fact that the fall of potential across any portion of the wire is directly proportional to the length of that portion provided the wire is of uniform area of cross-section and a constant current is flowing through it. To shift the balance point on higher length, the potential gradient of the wire is to be decreased. The same can be obtained by decreasing the current of the main circuit, which is possible by increasing the resistance in sereis of potentiometer wire.