How does a simple circuit work


A simple circuit is made up of a (power) generator (a voltage or current source) and a (power) consumer, which are connected to one another via cables. The circuit can be closed and interrupted by a switch. This controls whether a current flows in the circuit or not.
The power generator provides the voltage and the current. It can be a power supply, a dynamo, a battery, or something similar. A power consumer can be a resistor, a motor, a lightbulb, or something similar.
In order to simplify the representation of the circuit, standardized symbols (circuit symbols) are used, which are connected to one another and illustrate the work of the components in the circuit.

Fuse in the circuit

Usually each circuit is protected by a fuse. The fuse reacts from a certain current and interrupts the circuit. This protects all parts of the circuit from overload and short-circuit.
A short circuit is the condition when the plus pole and the minus pole of a voltage source have a direct connection (0 Ω).
If the voltage of the voltage source is too high (AC voltage = 50V, DC voltage = 120V), there is a danger to people if they cause this short circuit (with a body resistance of approx. 1 to 1.5 kΩ).

Note: There's a reason the fuse needs to be at the beginning of the circuit. The fuse should switch the circuit voltage-free. If the light source is defective, it can be safely replaced. There would be a risk if the fuse were switched after the lamp. If the fuse were removed and the circuit switched on, there would be contact between the circuit and the earth, then there would be an earth fault (danger to life). That is why the fuse is always installed at the beginning of the circuit and not somewhere in between

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