Name: Conversion of a Galvanometer Into a Voltmeter
Uploaded: 2019-07-19
Duration: 7 min 18 s
Description: This video helps us understand the working of a galvanometer. It also teaches us how to convert it into a voltmeter of the desired range both theoretically a...

Question

Define or describe a Potentiometer.

Accepted Answer

A potentiometer is a type of position sensor. They are used to measure displacement in any direction. Linear potentiometers linearly measure displacement and rotary potentiometers measure rotational displacement.

Let us consider the length of uniform wire AB as $l_{AB}$ with its uniform cross-sectional area as $A$ and $R_{AB}$ as its resistance. Let $I$ be the steady current flowing through the wire. Let $V_{AB}$ be the potential difference across the ends of the wire. Let $ρ$ be the specific resistance of the material of the wire.
When there is no current in the galvanometer, the voltage across the points A and P, say $V_{A P}$ must be equal to the EMF of the battery $E$ .
Therefore, $V_{A P} = E - - (1)$
Say, the resistance of the wire between A and P is $R_{A P}$ . We can say that,
$\frac{V_{A P}}{V_{A B}} = \frac{R_{A P}}{R_{A B}} - - (2)$
From $(1)$ and $(2)$ , we get, $E = V_{A B} \frac{R_{A P}}{R_{A B}} - - (3)$
We know the resistance of a material is proportional to its length for a given cross-section. Hence, $\frac{R_{A P}}{R_{A B}} = \frac{A P}{A B} - - (4)$
From $(3)$ and $(4)$ , we can write, $E = V_{A B} \frac{A P}{A B}$
This way, we can find the EMF of a battery or voltage across two points in a circuit using a potentiometer.

Define or describe a Potentiometer.

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