In the circuit shown in figure switch `S` is thrown to position 1 at `t=0`. when the current in the resistor is `1A`, it is shifted to position 2. the total heat generated in the circuit after shifting to position 2 is

Options

A. zero
B. `625muJ`
C. `100muJ`
D. none of these

Answer

C

Explanation

In position 1, initial maximum current is
`i_0=V/R=10/5=2A`
At the given time given current is 1A or half of the above value. Hence at this is instant capacitor is also charged to half of the final value of 5V.
Now, it is shifted to position -2 wherein steady state it again charged to 5V but wilth opposite polarity.
`U_i=U_f=1/2CV^2 (.:'V=5V)`
`:.` Total energy supplied by the lower battery is converted into heat. But double charge transfer (from the normal) takes place from this battery.
`:. "Heat produced =energy supplied"` by the battery
`=(/_\q)V=(2CV)(V)=2CV^2`
`=2xx2xx10^-6xx(5)^2`
`=100xx10^-6J`
`=100muJ`