Step 1 of 6 Basic electric circuits
The loop
Electricity only flows when it has a complete path: out of the battery, through the bulb, and back again. That path is called a circuit, from the word "circle".
There's a gap in this circuit. Tap the floating piece of wire to drop it into the gap.
What does the switch actually do? Try it.
Step 2 of 6 Basic electric circuits
Push, flow and hold-back
Three ideas explain almost everything in a circuit. The battery gives a push. That push makes charge flow round the loop. Everything in the way, like the thin wire in a bulb, holds back the flow.
A useful picture is water in a pipe: a pump pushes, water flows, a narrow section holds it back. It's only a picture, though: nothing "fills up" inside a real wire.
Match each everyday word to its proper name. Tap a word, then its name.
When you flip a switch, the light comes on almost instantly. So how fast do the electrons in the wire actually move?
Step 3 of 6 Basic electric circuits
One rule
Push, flow and hold-back are tied together by one rule: flow = push ÷ hold-back. In proper names, current = voltage ÷ resistance, usually written V = I × R. It's called Ohm's law.
Use the sliders to make exactly 2 amps flow.
Keep the push the same and double the hold-back. What happens to the flow? Try it with the sliders, then answer.
Step 4 of 6 Basic electric circuits
Nothing gets used up
A common picture is that a bulb "uses up" electricity, so less comes out than goes in. Here are two meters, one on each side of the bulb.
Half an amp (0.5 A) flows into the bulb. How much flows out the other side?
If the current isn't used up, what does a battery actually run out of?
Step 5 of 6 Basic electric circuits
In a line, or side by side
Two bulbs can share one battery in two ways. In a line (called series), the current goes through one bulb and then the other. Side by side (called parallel), each bulb gets its own path.
Find the layout where both bulbs shine as brightly as one bulb would on its own.
Tap a bulb to unscrew it, and again to put it back.
Switch back to in a line and unscrew one bulb. What happens to the other one?
Step 6 of 6 Basic electric circuits
When it goes wrong
A short circuit is a shortcut with almost no hold-back. With so little resistance, a huge current flows and wires get dangerously hot. A fuse is a deliberately thin wire that melts first and breaks the loop.
Make a short circuit: tap the dashed line to give the current a shortcut around the bulb.
A bird can sit on a single bare power line carrying thousands of volts. Why doesn't it get a shock?
Quiz Basic electric circuits
Check what you know
Six questions, 5 points each. One answer per question.
Done Basic electric circuits
Lesson complete
Now you know what really happens when you flip a light switch: you close a loop, the battery's push sets the whole loop flowing at once, and the bulb turns some of that energy into light.
MARIFA · MVP1 · Nothing you do here leaves this device.