Electricity: what actually flows in a wire
Charge, voltage and current — the three things you need before a signal can mean anything.
Inside a metal wire sit electrons that are free to move. Normally they drift in every direction and nothing useful happens. Push them so that more of them move the same way than the other, and you have a current: charge in motion.
Three quantities describe the whole picture. Voltage (volts) is the difference that pushes. Current (amperes) is how much charge passes each second. Resistance (ohms) is what opposes the flow. They are tied together by Ohm's law: voltage = current × resistance. Raise the voltage and more current flows; raise the resistance and less does.
Current needs a complete loop. Leave the battery, go through the lamp, and come back to the other end of the battery. Break the loop anywhere — an open switch, a cut wire — and everything stops instantly, everywhere in that loop.
Water analogy, kept honest: pressure at the top -> VOLTAGE (measured in volts, V) litres per second -> CURRENT (measured in amperes, A) narrow pipe -> RESISTANCE (measured in ohms) voltage = current x resistance (Ohm\'s law) Same pressure, narrower pipe -> less water per second. Same pipe, more pressure -> more water per second.
Practice
Match each electrical quantity with what it means in the water analogy.
Hints
- Voltage is what pushes, current is how much actually flows.
- The narrow pipe does not push the water — it slows it down.
12 XP
The switch is open. What happens to the current in the circuit?
Hints
- Current needs a way back to where it started.
- A switch that is open leaves a gap in the ring.
10 XP
Order what happens in a circuit from the moment the switch closes.
Hints
- Nothing moves until there is a difference between the two ends.
- The same electrons that leave the battery are the ones that come back to it.
11 XP