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A potentiometer having the potential gra...

A potentiometer having the potential gradient of `2 mV//cm` is used to measure the difference of potential across a resistance of `10 ohm`. If a length of `50 cm` of the potentiometer wire is required to get null point, the current passing through the `10 ohm` resistor is (in `mA`)

A

10

B

20

C

30

D

40

Text Solution

Verified by Experts

The correct Answer is:
C
`vec(a)_(cm) = (m_(1)vec(a)_(1) + m_(2)vec(a)_(2))/(m_(1) + m_(2)) = (1 (-2hat(i)) + 2 (-2 hat(j)))/(1 + 2)`
`= -(2)/(3)(hat(i) + 2hat(j))m//s^(2)`
By using `vec(v)_(cm) = vec(u)_(cm) + vec(a)_(cm)t`, we get `t = 3s`
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