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In given circuit all capacitor were unch...

In given circuit all capacitor were uncharged initially. First switch `S_(1)` is closed for long time. When circuit reaches to steady state `S_(1)` is opened and `S_(2)` closed.
The current through `R_(2)` jus after closing the switch `S_(2)` is

A

`0.75mJ`

B

`1.5mJ`

C

`3mJ`

D

`2.25mJ`

Text Solution

Verified by Experts

The correct Answer is:
B
Situation just before closing `S_(2)`

`7.5-x/60-x/30=0`
`7.5=x/20impliesx=150muC`
Voltage across `S_(2)=5V`
Just after closing `S_(2)`
`x/30+5-2i=0`
`2i=10`
`i=5A`
Charge flown through `5V` battery
`=300muC`
Work done by `5V`s battery
`W_(1)=1500muJ=1.5mJ`
Energy stored in`30muF` capacitor at `t=0` is same as at `t=oo`
So heat produced in circuit `1.5mJ`
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