Maths With Matt · Interactive Physics
DC Circuit Builder
Build textbook circuits, investigate current and potential difference, and explore component I–V characteristics in real time.
Selected component
Select a component in the circuit area to reveal its controls.
Circuit I–V characteristics
All current components are shown; coloured points are their live operating points.
Capacitor charge trace
Run the circuit to trace charge against time.
Build a DC circuit and explain the readings
Use this free DC circuit builder to connect a circuit diagram to current, potential difference and resistance. Start with a working example, predict what the meters will show, then change one component at a time.
Current, voltage and resistance
Current is the rate of flow of charge. Potential difference is energy transferred per unit charge. For a resistor at constant temperature, V = IR: doubling the potential difference doubles the current when resistance stays constant. A 6 V supply across a 12 Ω resistor gives a current of 0.50 A and transfers energy at a rate P = VI = 3.0 W.
Investigate series and parallel circuits
In a series path, the current is the same through each component and the potential differences add to the supply voltage. Across parallel branches, the potential difference is the same and the branch currents add at a junction. Predict how adding resistance will change the supply current before running your circuit.
Connect the circuit to an I–V graph
Use the component I–V characteristics to distinguish an ohmic resistor from a filament lamp or diode. Resistance is V/I at a point; it is not generally the gradient of an I-against-V graph. Real components may heat up, and a model cannot replace laboratory measurements.
Next, compare the series and parallel circuits simulation, practise A-Level electricity questions, or explore all free physics simulations.