Electricity

How does an electric circuit work? Why does copper conduct electricity and rubber does not? What is the difference between series and parallel circuits? And how are current, voltage and resistance related? Here you work out the basics of electricity step by step and practise on every page. In the exercises you build circuits yourself. For grades 5 to 8: first the circuit, then the quantities with Ohm's law. It is about direct current, as batteries supply it; alternating current comes later.

The electric circuit
For a lamp to light up, the current must be able to flow in a circle. Here you find out which materials let it through.
1. The simple circuit A battery, a lamp and wires form a circuit. It must be closed for the lamp to light up.
2. Conductors and insulators Metals conduct electricity; rubber, glass and plastic do not. That is how you can tell what cables are made of.
Circuits
Switches, circuit symbols, series and parallel circuits. On the pages you build circuits yourself and see how the current runs.
1. Switches and circuit symbols A switch opens and closes the circuit. In a circuit diagram you draw parts as circuit symbols.
2. Series circuit In a series circuit the lamps are connected one after the other. If one fails, all go out.
3. Parallel circuit In a parallel circuit every lamp has its own path. If one fails, the others keep shining.
Electricity in everyday life
What electric current does, and how to handle it safely.
1. Effects of electric current Current can produce heat, light and magnetism. Many devices work this way.
2. Staying safe with electricity Sockets, batteries and thunderstorms. You learn what is dangerous and what is not.
Quantities in the circuit
Current, voltage and resistance: what they mean, how you measure them and how Ohm's law links them. This is about direct current, as batteries supply it.
1. Current The current tells you how much electric current flows. You measure it with an ammeter, in amperes (A) and milliamperes (mA).
2. Voltage The voltage drives the current. You measure it with a voltmeter, in volts (V), in parallel with the part.
3. Resistance The resistance tells how strongly a part hinders the current. It is measured in ohms (Ω) and depends on the material, length and thickness.
4. Ohm's law Voltage, current and resistance are linked: R = U / I. With it you calculate a missing quantity.
Circuits with meters
Predict and calculate current and voltage in series and parallel circuits, switch on and check on the meter.
1. Series circuit with meters In a series circuit the current is the same everywhere, and the voltages of the resistors add up.
2. Parallel circuit with meters In a parallel circuit every branch has the same voltage, and the branch currents add up to the total current.

Glossary

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Sources

The facts in this app come from these sources: