VoltLab Circuit Lab
A virtual electronics workbench: build circuits and observe current, voltage and component behavior in real time, with instruments and data recording.
Chapters
Series and parallel circuits
Three small light bulbs form a mixed circuit, and the changes in brightness and current of each light when the switch is turned on and off are observed.
Explore Ohm's Law
Use a sliding rheostat to change the voltage across the fixed value resistor, record multiple groups of U and I, and draw a U-I image to find the resistance.
Measure the electromotive force and internal resistance of the power supply
Use voltammetry to measure an old dry cell battery (E=1.5V, r=1Ω). E can be obtained from the vertical intercept of the U-I diagram, and r can be obtained from the slope.
Plot a filament lamp's current–voltage characteristic
The sliding rheostat voltage-divided connection method adjusts the bulb voltage from 0 to obtain a curved U-I curve.
RC circuit charging and discharging
The single-pole double-throw switch switches the charging and discharging of the capacitor. The exponential curve is observed on the oscilloscope. The time constant is τ = RC = 1 s.
Self-induction phenomenon after power outage
The light bulb is connected in parallel with the large inductor coil. When the switch is turned off, the light bulb flashes and then goes out.
LC oscillation circuit
Charge the capacitor, then switch to the inductor to observe damped exchange of electric and magnetic field energy.
Bridge rectification and capacitor filtering
Four diodes convert 50 Hz AC into pulsating DC. A filter capacitor smooths the waveform.
Wheatstone bridge resistance measurement
Adjust R3 until the galvanometer reads zero. At balance, Rx = R2·R3 / R1.
Series RLC resonance
Vary the source frequency. Current peaks at f₀ = 1/(2π√LC) ≈ 503 Hz, and capacitor voltage can greatly exceed source voltage.
Transformer principles
The primary-to-secondary turns ratio is 2:1. RMS voltmeters verify U₁/U₂ = n₁/n₂.
One-way diode conduction
A 1 Hz AC source drives antiparallel red and green LEDs, which light alternately.
Transistor-controlled streetlight
A photoresistor and transistor form a light-sensitive switch: the LED turns on when it gets dark.
DC motor
Observe motor starting current, back EMF, and the effects of load on speed and current.
Short circuits and fuses
Close the short-circuit switch: current surges and the fuse melts to protect the circuit.
Zener voltage regulator
In reverse breakdown, a Zener diode keeps nearly constant voltage, maintaining about 5.1 V across the load despite source fluctuations.
Explore Joule's law
Two flasks contain equal masses of kerosene. Series heater wires of 5 Ω and 10 Ω heat them; compare temperature rises over the same time.
Factors affecting a conductor's resistance
Four wires vary in material, length and cross section. Connect each in turn and compare current.
Using a multimeter
Measure the resistance box on the Ω range and battery voltage on DC voltage; click the meter dial to change ranges.
Factors affecting electromagnet strength
Move the rheostat to change current and watch the number of attracted pins. Also vary turns and remove the iron core.
Solar-powered motor
A lamp illuminates a solar panel that powers a small motor. Vary illumination and observe speed, voltage and current.
Blank workbench
Clear the workbench and build your own circuit using components from the left library.
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