When a p-type semiconductor is brought into a close contact with n-type semiconductor, we get a p-n junction with a barrier potential `0.4V` and the width of depletion region is `4.0 xx 10^(-7)m`. this p-n junction is forwaed biased with a battery of voltage `3V` adn negligible internal resistance, in series with a resistance of resistance R, ideal milliammeter and key K as shown in Fig.

The resistance of resistor R is

Options

A. `150 Omega`
B. `300 Omega`
C. `130 Omega`
D. `180 Omega`

Answer

C

Explanation

Pot. Diff. across `R=3-0.4=2.6 V`
Resistance, `R=("pot. diff.")/("current")=2.6/(20xx10^(-3))=130 Omega`