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

Options

A. `1.5`
B. `4.5`
C. `3.0`
D. `2.0`

Answer

C

Explanation

`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`