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Question:

The figure shows an experimental plot for discharging of a capacitor in an RC circuit. The time constant τ of this circuit lies between:

150 sec and 200 sec

0 and 50 sec

100 sec and 150 sec

50 sec and 100 sec

Solution:

For discharging of an RC circuit, V = V₀e⁻ᵗ⁄τ
So, when V = V₀/2, ln(1/2) = -t/τ
τ = t/ln2
From graph we can say that at t = 100 sec, V = V₀/2
τ = 100/ln2
τ = 144.3