Concepts Of Physics MCQ Edition [Volume 2]PhysicsElectric Current in Conductors
In the circuit depicted in the figure, the capacitors are initially uncharged. If the switch is closed at t = 0 , determine the charge on the capacitor C₁ as a function of time t .
Options
- AE C₁ C₂ C₁ + C₂ ( 1 - e^ - t(C₁ + C₂) r C₁ C₂ )
- BE C₁ ( 1 - e^ - t r C₁ )
- CE C₁ C₂ C₁ + C₂ ( 1 - e^ - t r C₁ + C₂ )
- DE (C₁ + C₂) ( 1 - e^ - t r(C₁ + C₂) )
Correct answer
A. E C₁ C₂ C₁ + C₂ ( 1 - e^ - t(C₁ + C₂) r C₁ C₂ )
Step-by-step solution
The given circuit is an RC circuit with two capacitors C₁ and C₂ connected in series with a resistor r . The equivalent capacitance of the series combination is: C_ eq = C₁ C₂ C₁ + C₂ The time constant of the circuit is: = r C_ eq = r C₁ C₂ C₁ + C₂ The maximum steady-state charge on the equivalent capacitor is: q₀ = E C_ eq = E C₁ C₂ C₁ + C₂ The charge on the equivalent capacitor as a function of time is given by the standard charging equation: q(t) = q₀ ( 1 - e^ - t ) Since the capacitors are in series, the charge