Find Time Constant for RC Circuit: Solve the Equation!

[utkarshakash]

Homework Statement

The time constant of charging for the capacitor shown in the figure is

Homework Equations

See attached diagram

The Attempt at a Solution

$\tau = R_{eq} C$

$R_{eq} = R/2$

So the answer should be t= RC/2. But the correct answer is 0!

 

[gneill]

Once the switch is closed all the components are in parallel, right? What's the rule for the potential across components in parallel?

 

[utkarshakash]

Once the switch is closed all the components are in parallel, right? What's the rule for the potential across components in parallel?

They all have the same potential difference.

 

[gneill]

They all have the same potential difference.

Right. And if the voltage source is ideal and the wires have entirely negligible resistance, then the capacitor voltage immediately after the switch closes must be...

 

[utkarshakash]

Right. And if the voltage source is ideal and the wires have entirely negligible resistance, then the capacitor voltage immediately after the switch closes must be...

It should be V. Thus time constant must be 0. Thanks !