1.

In the circuit shown, keys `K_1` and `K_2` both are closed the ammeter reads `I_0`. But when `K_1`is open and `K_2` is closed, the ammeter reads `I_0//2`. Assuming that ammeter resistance is much less than `R_2`, the values of `r` and `R_1` is Omega are A. 25,50B. 25100C. 0,100D. 0,50

Answer» Correct Answer - D
When `K_1` and `K_2` both are closed `R_1` is short circuited,
`R_("net")=(50+r)Omega`
When `K_1` is open and `K_2` is closed, current remains half.
Therefore, net resistance of the circuit becomes two times.
or `(50+r)+R_1=2(50+r)`
of the given options the above equation is satisfied if
`r=0` and `R_1 =50 Omega`


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