Which of the following statements are correct for the RC circuit shown? After S

ID: 2308443 • Letter: W

Question

Which of the following statements are correct for the RC circuit shown?

After S is moved to b, it takes a time ? = RC, for the charge on C to drop to 1/e of its initial value.

After S is in the position b for a long time, the current through R becomes close to zero.

The longer S is kept in the position a, the lower is the energy stored in C.

If S is in the position a for a long time, the current through R approaches ?/R.

If S is in the position a for a long time, the charge on C approaches zero.

Right after S is moved to the position a, following a long time in the position b, the current through R is ?/R.

Right after S is moved to the position b, following a long time in the position a, the current through R is zero.

Thank you. Use short explanations if you can.

ANSWER :

The correct options are :

(a) After S is moved to b, it takes a time = RC, for the charge on C to drop to 1/e of its initial value.

Explantion :

After S is moved to b :

charge stored on C , Q = Qo*e^(-t/RC)

where Qo = initial charge

So, for t = RC, Q = Qo*e^(-RC/RC) = Qo/e

So, charge becomes 1/e times the initial charge

(b)

Right after S is moved to the position a, following a long time in the position b, the current through R is /R.

Explanation:

right after S is moved to position a, the capacitor acts as a short circuit path

So, current through the circuit : I = E/R <----proved

All other options are incorrect

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