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Practical electrical and electronic circuitsOutput devices

Measurement and analysis of current and voltage in simple circuits allows us to formulate rules and predict unknown values.

Part of PhysicsElectricity

Output devices

Energy converters

Output devices in electronic systems transform electrical energy into another type of energy, such as light, sound or .

Common output devices and their associated energy changes are shown in the table below.

Table with device and what it converts electrical energy to: Buzzer - sound, Loudspeaker - sound, Lamp - light, Light Emitting Diode (LED) - light, Motor - kinetic, Relay - kinetic

A special output device: Light Emitting Diode

Unlike filament lamps, where electrical energy must be converted into heat before light can be produced, Light Emitting Diodes (LEDs) are able to transform electrical energy directly into light energy.

Since the LED is a diode, it will only light up when current is in the correct (conducting) direction.

Series circuit with a battery, an LED and a lamp
Diode in position allowing current

When drawing an LED circuit, the tip of the triangle in the LED symbol (shown below) must point towards the negative terminal of the power supply or the LED will not work.

LED symbol: a vertical line with a triangle pointing down and a horizontal line at the bottom of the triagle. Two short arrows point away from it to the bottom right. The upper part is labelled 'positive terminal' and the lower part is labelled 'negative terminal'.

In some circuits the current in an LED circuit must be limited to avoid damaging the LED.

A series resistor is used to reduce current in the circuit and ensure the LED is not damaged.

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Calculating the value of the series resistor
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Voltage dividers

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