A parallel-plate capacitor has plate area 20 cm², plate separation 1.0 mm and a dielectric slab of dielectric constant 5.0 completely filling the space. It is connected to a 6.0 V battery through a 100 kΩ resistor. Find the energy stored in the capacitor 8.9 µs after the connection is made.
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Question

A parallel-plate capacitor has plate area 20 cm², plate separation 1.0 mm and a dielectric slab of dielectric constant 5.0 completely filling the space. It is connected to a 6.0 V battery through a 100 kΩ resistor. Find the energy stored in the capacitor 8.9 µs after the connection is made.

Options

G1 Physics · Accepted Answer

C = Kε₀A/d ≈ 8.85×10⁻¹¹ F and τ = RC ≈ 8.85 µs. At t = 8.9 µs, the capacitor voltage is 6[1−e^(−t/τ)] ≈ 3.80 V. Hence U = ½CV² ≈ 6.4×10⁻¹⁰ J, so option B.