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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Electric Current in Conductors

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Current in Conductors

A capacitor with a capacitance of 8.0 is wired to a battery of emf...

A capacitor with a capacitance of 8.0μF8.0 \mu\text{F} is wired to a battery of emf 6.0 V6.0 \text{ V} via a resistance of 24Ω24 \Omega. Determine the current in the circuit exactly one time constant after the connections are made.

Options

  1. A0.25 A0.25 \text{ A}
  2. B0.09 A0.09 \text{ A}
  3. C0 A0 \text{ A}
  4. D0.16 A0.16 \text{ A}

Correct answer

B. 0.09 A0.09 \text{ A}

Step-by-step solution

The current in an RC circuit during charging is given by the equation:

I(t)=I0e−t/τI(t) = I_0 e^{-t/\tau}

where I0=VRI_0 = \dfrac{V}{R} is the initial current and τ=RC\tau = RC is the time constant.

At exactly one time constant, t=τt = \tau, the current becomes:

I(τ)=I0e−1=I0eI(\tau) = I_0 e^{-1} = \dfrac{I_0}{e}

The initial current I0I_0 is:

I0=6.024=0.25 AI_0 = \dfrac{6.0}{24} = 0.25 \text{ A}

Substituting I0I_0 and the value of e≈2.718e \approx 2.718 into the equation for current:

I(τ)=0.252.718≈0.09 AI(\tau) = \dfrac{0.25}{2.718} \approx 0.09 \text{ A}
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