The threshold voltage for a p-n junction diode used in the circuit is 0.7 V and a resistance of 100 Ω is connected with diode in series. The current in the circuit is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 0 A
A p-n junction diode conducts appreciably only when it is forward biased and the forward voltage across it exceeds its threshold (knee) voltage, here 0.7 V.
Reading the figure: the longer plate of the 0.5 V cell is on the left, so the cell drives current through D in its forward direction; the diode is forward biased. But the cell provides less than the threshold voltage:
\( V = 0.5\,\mathrm{V} \lt V_{\mathrm{th}} = 0.7\,\mathrm{V} \)
The potential barrier is not overcome, so practically no current flows.
\( I = 0\,\mathrm{A} \)