You will come across the term 'resistance' in the context of both hydraulics and electrics. In hydraulics, oil encounters resistance as it flows around a circuit.

In electricity, a resistor is an electrical device that is used to restrict the flow of electricity in a circuit, or to drop the voltage of a supply down to a lower value.

Symbols for resistor

For example, we often use resistors to protect the base emitter circuits in transistors:

Base limiting resistor

Resistance can be thought of as the property of a circuit that converts electrical energy into heat energy. This is because the circuit opposes the flow of electrical current.

Where ever you can feel heat in an electrical circuit, that is a sure sign of resistance.

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