Question 505: Current Electricity

Question

If the length of the potentiometer wire is increased by keeping constant potential difference across the wire, then

Accepted Answer

If the length of the potentiometer wire is increased while the potential difference (V) across it remains constant, let's see what happens:
The potential gradient ($k$) along the potentiometer wire is:
$$ k = \frac{	ext{Potential difference across the wire (V)}}{	ext{Length of the wire (L)}} $$
So,
$$ k = \frac{V}{L} $$
If $L$ increases and $V$ is constant, then $k$ decreases.
To obtain the null point, the potential difference across a certain length $l$ of the potentiometer wire must be equal to the emf of the cell connected to it:
$$ 	ext{emf} = k \cdot l $$
Since $k$ has decreased, to balance the same emf, $l$ (the length to the null point) must increase.
Correct option:
Option C
the null point is obtained at larger distance.

Answer

the null point is obtained at shorter distance.

Answer

the potential gradient is increased.

Answer

the null point is obtained at larger distance.

Answer

there is no change in the null point.

Current Electricity

If the length of the potentiometer wire is increased by keeping constant potential difference across the wire, then

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