In an experiment with a potentiometer, VB = 10 V. R is adjusted to be 50 Ω (figure). A student wanting to measure voltage E1of a battery (approx. 8V) finds no null point possible. He then diminishes R to 10 Ω and is able to locate the null point on the last (4th )segment of the potentiometer, find the resistance of the potentiometer wire and potential drop per unit length across the wire in the second case.

Q : In an experiment with a potentiometer, VB = 10 V. R is adjusted to be 50 Ω (figure). A student wanting to measure voltage E1of a battery (approx. 8V) finds no null point possible. He then diminishes R to 10 Ω and is able to locate the null point on the last (4th )segment of the potentiometer, find the resistance of the potentiometer wire and potential drop per unit length across the wire in the second case.

Numerical