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Electricity & Magnetism: fun facts and quiz
The essentials in 7 ideas, with fun facts, an illustrated story and a quiz to see how much you know.
The essentials
Electric Current
Electric current is a flow of tiny charged particles, usually electrons, through a wire. It needs a complete loop, called a circuit.
Key fact
Current is measured in amps, named after André-Marie Ampère.
Conductors & Insulators
Conductors, like copper, let electricity flow easily. Insulators, like rubber and plastic, block it. Wires use both.
Key fact
Pure water barely conducts; it’s the dissolved salts that do.
Magnets
Magnets have a north and a south pole. Opposite poles attract; like poles repel. Earth itself behaves like a giant magnet.
Key fact
Cut a magnet in half and you get two magnets, each with two poles.
Static Electricity
Rubbing a balloon on your hair moves electrons, leaving charges that make your hair stand up. Lightning is static electricity on a gigantic scale.
Key fact
A lightning bolt can reach about 30,000 °C, hotter than the Sun’s surface.
Electromagnets
Electricity and magnetism are linked: current through a coil makes a magnet you can switch on and off. Electromagnets lift scrap cars, ring doorbells and drive speakers.
Key fact
Hans Christian Ørsted discovered the link in 1820.
Generators
Moving a magnet near a coil of wire makes electricity flow. That’s how most power stations work, whether they’re turned by steam, wind or water.
Key fact
Michael Faraday discovered this in 1831.
AC & DC
Batteries give direct current (DC), which flows one way. Mains power is alternating current (AC), switching direction 50 or 60 times a second.
Key fact
Edison backed DC and Tesla backed AC in the “war of the currents”.
Fun facts
Electrons drift through a wire surprisingly slowly, often less than a millimetre per second. It’s the push that travels fast.
Silver is the best conductor of all, but copper is nearly as good and far cheaper, so wires use copper.
Heat a magnet enough and it stops being magnetic. For iron, that happens above about 770 °C, its Curie point.
A rubbed balloon can hold thousands of volts, yet it’s harmless: the amount of charge is tiny.
MRI scanners use electromagnets tens of thousands of times stronger than Earth’s magnetic field.
Faraday had little schooling and started out as a bookbinder’s apprentice.
Europe’s mains electricity runs at 50 hertz; North America’s runs at 60.
Story: A Kite in the Storm
A Kite in the Storm
June 1752, Philadelphia. Benjamin Franklin suspects lightning is electricity, like the sparks from a rubbed glass jar.
He flies a kite into a storm cloud, with a metal key tied to the wet string. Sparks leap from the key to his knuckle.
Lightning was electric. His lightning rod, invented from the same idea, still protects buildings today.
True or false?
Tap your answer to see if you got it, and why.
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Question 1 of 10
Electricity needs a complete circuit to flow.
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True. Break the loop and the current stops.
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Question 2 of 10
Rubber is an electrical insulator.
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True. It blocks the flow of current.
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Question 3 of 10
Opposite magnetic poles attract.
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True. North pulls south.
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Question 4 of 10
Lightning is a huge discharge of static electricity.
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True. Charge builds up in storm clouds.
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Question 5 of 10
An electric current can create a magnetic field.
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True. That’s how electromagnets work.
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Question 6 of 10
Moving a magnet near a coil can generate electricity.
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True. Faraday showed it in 1831.
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Question 7 of 10
Mains electricity is alternating current.
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True. It changes direction many times a second.
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Question 8 of 10
Electric current is measured in litres.
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False. It’s measured in amps.
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Question 9 of 10
Plastic is a good conductor of electricity.
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False. It’s an insulator, used to wrap wires.
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Question 10 of 10
Two north poles pull towards each other.
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False. Like poles push apart.
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