RC Charging and Discharging Virtual Lab

1. Build and operate the RC circuit

Click Build Circuit. Select a mode with S1 and use S2 to start or halt the stopwatch. You may switch to discharging at any point; S1 resets the stopwatch and stores the capacitor voltage as the 0 s discharge reading.

Circuit not built

DIGITAL STOPWATCH000.0SECONDS · S2

DIGITAL VOLTMETER0.00VOLTS · CAPACITOR

S1 — Circuit mode

S1 changes the circuit mode. Switching S1 to discharging is allowed at any time. The stopwatch resets to zero and the voltage immediately before switching is recorded as the 0 s discharge voltage.

S2 — Timer control

Before you begin: Build the circuit. Then select S1 mode and use S2 to start the timer.

Voltage against time

Charging continues gradually toward 4.20 V. Switch S1 to discharging at any point; the voltage at switching is automatically recorded at 0 s.

2. Experimental settings

DC power supply5.0 VFixed supply voltage

Series resistance220 kΩFixed for the experiment

Simulation speed 1×

Charging: V_C = V_S(1 − e^−t/RC)
Discharging: V_C = V_initiale^−t/RC
Time constant: τ = RC

3. Experimental observations

Charging stageNot started

Discharging stageNot started

Switch S1 to discharging whenever you choose. The voltage at the instant of switching is stored as the 0 s discharge reading.

4. Dielectric constant from the graph

After recording both charging and discharging readings, use the intersection of the two measured curves to obtain t′. The result remains hidden until you click Calculate.

t′ = intersection time from graph
C = t′/(0.693 R)
ε_r = [t′/(0.693 R ε₀)] × (d/A)

Graph intersection time, t′—

Calculated dielectric constant, εrNot calculated

Use R = 220 kΩ, ε₀ = 8.854 × 10⁻¹² F m⁻¹ and d/A = 1.4 × 10⁻⁷ m⁻¹. The calculated value depends on t′ obtained from the graph.

Record readings in both modes first. No numerical dielectric result is shown before calculation.

5. Observation table

Click “Record next 10 s reading” while the timer is close to 10, 20, 30, …, 80 s. The timer continues running and the measured voltage is stored in the appropriate charging or discharging column. A matching pair of curves is required to calculate t′.

Time (s)	Charging voltage (V)	Discharging voltage (V)
Build the circuit and record readings to populate this table.

6. Operating procedure

Click Build Circuit.
Set S1 to Charging mode, then set S2 to START. The timer starts at zero and the capacitor voltage rises.
Record charging readings at 10 s intervals up to 80 s. Charging continues beyond this interval and approaches 4.20 V gradually.
At any chosen point, switch S1 to Discharging mode. The stopwatch resets automatically and the voltage just before switching is recorded in the discharging column at 0 s.
Click START on S2. The voltage decreases; record it every 10 s up to 80 s and observe the discharging curve.
Download the CSV file if you wish to process the readings separately.

Important: The capacitor voltage is not forced to zero when S1 changes mode. Switching S1 to discharging stores the current capacitor voltage at 0 s and resets the stopwatch.