CIRCUITS AND COMPONENTS

CIRCUITS AND COMPONENTS

1. Simple Circuits: The diagrams below showed lamps

connected in a parallel circuit and in a series circuit.

-The supply has live and neutral conductors. On an alternating current (AC) supply, the difference between live and neutral is that conductors on the neutral side of appliances are earthed.

2. Mains AC circuits and switchboards

Where an AC supply enters a building, it is connected to a switchboard. This has a number of switches to allow different circuits in the building to be switched on and off. Circuits include power circuits. These supply the power sockets (or sockets) for the plugs on appliances. Usually a circuit breaker is fitted to each circuit. This is a safety switch that switches off automatically if there is a problem. This may happen if a person touches a live conductor, or if there is a short circuit. A short circuit is when current flows directly from a live conductor to a neutral conductor- for example, due to damaged insulation. Circuit breakers also allow circuits to be switched off manually, to isolate them (switch them off safely) – for example, before maintenance work.

3. Printed and integrated circuits

The circuits in electrical appliances are often printed circuits, on printed circuits boards ( PCBs).These are populated with electrical components. Many appliances also contain small, complex integrated circuits – often called microchips (or chips ) – made from silicon wafers. They act as semiconductors, which can be positively charged at certain points on their surface and negatively charged at other points. This principle is used to make small circuits.

4. Electrical and electronic components

There are many types of electrical and electronic components. These can be used individually or combined with other components to perform different tasks. For example:

a. Sensors or detectors can sense or detect levels of – or changes in – values such as temperature, pressure and light.

b. Control systems use feedback from sensors to control devices automatically. For example, mechanical devices such as water valves may be moved or adjusted by servomechanisms – electrically powered mechanisms that are controlled automatically by signals (‘messages’) from sensors.

c. Logic gates are widely used in control systems. They send signals, in the form of low voltages, to other devices. An output signal from the logic gate is switched on or off, depending on the

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