Build a circuit from a battery, resistors, bulbs, switches and meters, and watch the current flow. Change a value and see the readings update at once.
Start with a ready-made series or parallel circuit, or draw your own with the Draw wire tool.
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The rules to remember
Ohm's law
V = I × R. The voltage across a resistor equals the current through it times its resistance. Power: P = V × I = I2R.
Series circuit
One path. The current is the same everywhere, the voltages add up to the battery voltage, and the resistances add: R = R1 + R2 + ... If one bulb fails, they all go out.
Parallel circuit
Several paths. Every branch has the same voltage, the currents add up, and 1/R = 1/R1 + 1/R2 + ... The total resistance is smaller than the smallest branch.
Using the meters
An ammeter goes in series: the current must flow through it. It has almost no resistance.
A voltmeter goes in parallel, across the component you want to measure. It has a very large resistance, so it takes almost no current. Put one in series by mistake and the current drops to nearly zero.
Never connect an ammeter straight across a battery: that is a short circuit.
Practise what you learned
Test yourself with chapter-wise MCQs and explanations:
This is a simplified model for learning: steady (DC) circuits with ideal wires and meters. The bulb is a 6 V, 3 W lamp whose resistance does not change with temperature.
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