Edexcel A-Level Physics Capacitor Charge and Discharge

Practise Edexcel A-Level Physics capacitor charge and discharge curves by interpreting exponential RC graphs, current and voltage.

Exam points

sketch exponential charging or discharging curves with correct initial and final values
use the RC time constant to read graph values or mark one, five and half-life intervals
apply capacitor charge equations to choose capacitance or find current, voltage and charge

[Maximum number: 4]

A student built the circuit shown. The capacitor was initially uncharged.

Figure for Question 4.4.102 - Capacitor charge and discharge curves question 1 — Edexcel A-Level Physics A2

She closed the switch and plotted a graph of current on ammeter $\mathrm{A}_{1}$ against time.

(a)

Explain how the current on ammeter A_2 would vary over the same time interval.

[ 2 ]

(b)

Determine the charge stored on the capacitor after 30 s .

Charge stored on capacitor after $30 \mathrm{~s}=$

[ 2 ]

Determine the area under the current–time curve, giving $Q\approx1.1\times10^{-3}\,\mathrm{C}$ (acceptable range $1.0\times10^{-3}$ to $1.2\times10^{-3}\,\mathrm{C}$ ). Alternatively, use Q=CV with $V=5.0\,\mathrm{V}$ .

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4.4.102 - Capacitor charge and discharge curves question 1

Question (a)

Question (b)