Electrical symbols

Electronic component are classed into either being Passive devices or Active devices. A Passive Device is one that contributes no power gain to a circuit or system. Examples are Resistors, Light Bulb, Electrical Heaters. Active Devices are components that are capable of generating voltages or currents. Examples are Batteries and other Electrical Curent & Voltage Sources.

By using schematics symbols we can represent real-life devices.

Resistance -This is a resistance, measured in units ohms ohms, . Most often it will be a resistor.

This is a source of emf (electromotive force) or voltage source, with a voltage of , measured in units of volts, V. The most common source you will see will be a battery. However, batteries are really not resistance-free. We can model this case by putting a 'resistor' in the circuit which has the same resistance as the batterys would have.

This is a current source, with a current of , measured in units of amperes , A. Current source is ideal model of electrical power source. The internal current source resistance is infinity. We can model real life battery by putting a 'resistor' in parallel with curent source.