In the connecting shows in Fig. 6.68, intially swich `K` is open and the capacitor is uncharged. Then the switch is closed and the capacitor is changed up to the steady state and the switch is opened again. Determine the values indicated by thee ammeter.
(Given : `V_(0) = 30 V`, `R_(1) = 10 k Omega`,

A long time after the swich was closed

Options

A. 2mA
B. 3 mA
C. 6 mA
D. none of these

Answer

A

Explanation

a. Just after closing, capacitor behaves as short circuit and all current flows
through it, hence ammeter reads zero.
After a long time, capacitor behaves as an open circuit and no current
flows through it. Therefore,
`i = v_0/(R_1+R_2) = 30/(10+5) = 2mA`
Just after reopening, potential difference across `R_2` remains the same
initially as charge on capacitor does not charge initially. Hence,
current remains the same.