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This is an electric circuit simulator.
Make circuits by dragging the components into place, then add meters from the box on the right to measure voltages and currents.
Using a voltmeter is easy: just drag the black and red probes to the points you want to measure between.
Ammeters have to be actually part of the circuit.
Break connections by clicking on a joint and using the scissors.
Try to keep your circuits tidy!
A series circuit
Make a circuit like this: two bulbs in series with a battery. Put ammeters in each connecting wire and look at the current readings on them. What can you say about current in a circuit?
If you click on the battery it will give you a slider so you can change the voltage. Try changing it and see what happens to the current readings and the brightness of the bulbs.
Try moving the probes of the voltmeter to measure the voltage across the other bulb and the voltage across the battery. What do you notice?
What happens to the bulbs if you disconnect one of the wires to one of the bulbs?
A parallel circuit
Now make this one: two bulbs in parallel with a battery. Put ammeters in the the wire joining the battery and in the two branches going to the bulbs. What do you notice about the currents? Try changing the battery voltage and see if what you've noticed is still true. Look carefully at what the electrons are doing as they go through each of the junctions between the wires.
Measure the voltage across the battery and across each of the bulbs. What do you notice? Does changing the battery voltage make a difference?
What happens to the bulbs if you disconnect one of the wires to one of the bulbs?
A more complex circuit
A circuit with two bulbs in series, which are then in parallel with a third bulb. Look at the currents in the circuit and the brightness of the bulbs. Also look at how fast the electrons are moving in each part of the circuit.
Try measuring the voltages in different parts of the circuit. Can you see how they add up?
What happens to the bulbs if you disconnect one of the wires to one of the bulbs? Is that what you'd expect?
Other things to try:
Add more bulbs to a simple series circuit, so they're in a chain one after the other. Do some measurements. Do they fit what you'd expect?
Try three or four single bulbs in parallel with each other.
Try three bulbs in series, with another single bulb in parallel with them.
Make up some more circuits of your own. Keep an eye on the movement of the electrons, and keep thinking about what you would expect the measurements to be and testing your ideas.
Electricity is a beautifully logical topic in physics, once you've got the basics.
Voltage is a measure of how much energy the battery is giving the electrons as they pass through the battery, and also how much energy is being converted to other forms as they pass through things in the rest of the circuit. Energy in = energy out.
Current is a measure of the number of electrons that pass through a point in the circuit each second. It doesn't get lost. The current into a junction = the current that comes out of it.
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