1.

In the following circuits PN - junction diodes D_1,D_2 and D_3 are ideal for the following potentials of A and B. The correct increasing order of resistance between A and B will be (i) -10V, -5V (ii) -5 V,-10V (iii) -4V,-12V

Answer»

`(i) LT (ii) lt (iii)`
`(iii) lt (ii) lt (i)`
`(ii) = (iii) lt (i)`
`(i) = (iii) lt (ii)`

Solution :`V_A=-10V and V_B =-5V`
Diodes `D_1 and D_3` are REVERSE biased and `D_2 ` is forward biased.

`implies R_(AB)=R+R/4+R/4=3/2R`
(ii) When `V_A = - 5V and V_B = -10 V`
Didoes `D_2` is reverse biased `D_1 and D_3` are forward biased

`implies R_(AB)=R/4+R/2+R/4=R`
(iii) In this CASE equivalent resistance between A and B is ALSO R,
HENCE (ii) = (iii) `lt` (i)


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