CHARGE · POTENTIAL DIFFERENCE · CURRENT

A capacitor. A little patience.

Charge it up. Let it discharge. See how resistance and capacitance change the pace.

Charging circuit

Ready to charge

Charge on capacitor

p.d. across capacitor

p.d. across resistor

Circuit current

Move through time 0 τ

The animation shows 8 time constants in 12 seconds of playback. Graphs and readings use physical time. Use the slider to inspect any instant.

FOUR VIEWS. ONE CIRCUIT.

Follow the change

Dashed: full curve · solid: elapsed time

Charge on the capacitor

p.d. across the capacitor

p.d. across the resistor

Current in the circuit

Charging: approaching the limit

During discharge, conventional current reverses direction around the circuit. The arrow follows it; the resistor voltage is measured as the drop along that current.

Predict, then check

1. Double the resistance. What changes about the initial current and the time constant?

2. Double the capacitance. Does the final charge change? Does the final capacitor voltage?

3. Move to one time constant. Compare the fraction charged with the fraction remaining during discharge.

At 5τ the change is about 99.3% complete; exponential curves approach their limits without reaching them at a finite time.

Explore capacitor charging and discharging

Adjust the battery or initial capacitor voltage, series resistance and capacitance. Follow charge, capacitor potential difference, resistor potential difference and current against physical time, and compare the changes at one and five time constants.

Supports capacitor and RC circuit topics in IB Physics HL, A Level Physics and AP Physics C: Electricity and Magnetism.