Question

Copper is not used as potentiometer wire because?

Answer 1

Hint: A potentiometer works on the idea of a uniform potential drop along the length of the potentiometer wire, allowing the length of wire for the null point to correspond to a specific value of potential and so calculating potential.

Complete step-by-step solution:
The potential declines across the resistor in a resistive circuit, not across the conductor, because the conductor allows for easy current conduction by definition. Copper, as a good conductor, will not show a smooth potential drop over its length. As a result, using a Copper wire as a potentiometer wire will be impractical. Because copper wire has a high temperature coefficient of resistance and low resistivity, it is not appropriate for potentiometers. As a result, even a slight change in temperature can result in a large change in resistance, affecting the experimental circumstances.


Additional Information:
If you insist on creating a potentiometer out of copper wire, consider the following options:
1. Use a very, very thin copper wire; because resistance is inversely related to cross-sectional area, a tiny wire will have a relatively high resistance. (This will be a sensitive device; the wire will need to be extremely thin in order to be useful)
2. Use a very long and thin Copper wire, with turns put close together so that it can fit in a length of at le1ast \[{10^2}m\] to provide appropriate resistance - as resistance is proportional to length. This may be a really accurate potentiometer if it's well-made.
3. Another possibility is to limit the usage of the potentiometer with Copper wire to the computation of cells with very low EMF values. The EMF of the driver cell used to establish potential drop should be very low.

Note:In the laboratory, the alloys constantan and manganin have traditionally been employed for coils in resistance boxes, rheostats, and wires in potentiometers and metre bridges. They have a high resistivity and a low temperature coefficient of resistance, making them ideal for this application.