A semiconductor P-N junction is to be forward biased with a battery of e.m.f. 1.5 Volt. If a potential difference of 0.5V appears on the junction which does not depend on current and on passing 10mA current through the junction there occurs huge Joule loss, then to use the junction at 5mA current, the resistance required to be connected in its series will be:

200 Ω

$V_R = (1.5 − 0.5) = 1V = IR$

$∴R=\frac{1}{5×10^{-3}}=200 Ω$