Find the equivalent resistance of the network shown in Fig.1 between the point p and Q, when the p-n junction diode used ideal one.

Explanation

(i) When potential of P is higher than that of Q, the junction diode in circuit is forward biased. Its resistance becomes zero. Now we shall have two resistance in parallel each of `10 Omega` between points P and Q. Their effective resistance between P and Q is
`R=(10xx10)/(10+10)=5Omega`
(ii) When potential of P is lower than that of Q, the p-n junction in circuit is reverse biased. Its resistance becomes infinite. No current flows in the arm of p-n junction diode. The current will flow through 10Omega resistance connected in parallel arm to p-n junction diode.
Therefor the resistance of circuit is 10Omega