State the underlying principle of a potentiometer. Write two factors b

1.	State the underlying principle of a potentiometer. Write two factors by which current sensitivity of a potentiometer can be increased. Why is a potentiometer preferred over a voltmeter for measuring the emf of a cell?
Answer» Principle: The potential drop across a part of the potentiometer wire is directly proportional to the length of that part of the wire of uniform cross section. V = kl Where k is potential gradient. Current sensitivity of potentiometer wire is also known as potential gradient, and it can be increased. (i) By increasing the total length of the wire, keeping terminal voltage constant. (ii) By connecting a suitable extra resistance R in series with the potentiometer. So, less amount of the current flows through the potentiometer wire. Reasons: At the balance point, there is no net current drawn from the cell, and cell is in open circuit condition. Voltmeter has some resistance, when connected across the cell. Some current is drawn, as a result emf of the cell decreases. Hence, emf of the cell cannot be measured by the voltmeter.

State the underlying principle of a potentiometer. Write two factors by which current sensitivity of a potentiometer can be increased. Why is a potentiometer preferred over a voltmeter for measuring the emf of a cell?

Answer»

Principle: The potential drop across a part of the potentiometer wire is directly proportional to the length of that part of the wire of uniform cross section.

V = kl

Where k is potential gradient.

Current sensitivity of potentiometer wire is also known as potential gradient, and it can be increased.

(i) By increasing the total length of the wire, keeping terminal voltage constant.

(ii) By connecting a suitable extra resistance R in series with the potentiometer. So, less amount of the current flows through the potentiometer wire.

Reasons: At the balance point, there is no net current drawn from the cell, and cell is in open circuit condition. Voltmeter has some resistance, when connected across the cell. Some current is drawn, as a result emf of the cell decreases. Hence, emf of the cell cannot be measured by the voltmeter.

State the underlying principle of a potentiometer. Write two factors by which current sensitivity of a potentiometer can be increased. Why is a potentiometer preferred over a voltmeter for measuring the emf of a cell?

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