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Electrical circuits: 2.2 Circuit symbols and symbolism used in drawing and constructing circuit diagrams

Doc Brown's Physics exam study revision notes

There are various sections to work through,

after 1 they can be read and studied in any order.

INDEX for physics notes on drawing and interpreting simple electrical circuits


2.2 Circuit symbols and symbolism used in drawing and constructing circuit diagrams

electrical circuit symbols for UK GCSE IGCSE physics AQA Edexcel OCR examination science course

These are the typical symbols to know for GCSE level exams in the UK

An extended look at circuit symbols and how to use them in circuit diagrams

circuit symbol for the wire in a electrical circuit.

circuit symbol for a T junction in the circuit wires.

circuit symbol for a closed switch, this completes a circuit so that it is 'on' and current flows.

circuit symbol for an open switch, this breaks a circuit so that it is 'off', and current can't flow.

circuit symbol for a two way switch, in which one route is 'open' and the other 'closed'.

, , , circuit symbols for 1, 2, 3 or many cells  wired in series (>1 cell often referred to as a 'battery'), the short stubby vertical line is the negative pole and the long thin vertical line is the positive pole.

Components in a series are wired in line with each other, end to end connecting with the +ve and -ve terminals of the power supply.

If you have two 1.5 V batteries wired in series, you add them up to get the total p.d. of 3.0 V.

You do exactly the same with resistors e.g. a 3.0 ohm and 5.5 resistor wired in series act as a total resistance of 8.5 ohms.

The 4th symbol often indicates a battery like that in a car, made up of multiple individual cells wired in series.

circuit symbol for two cells wired in parallel.

When components are wired in parallel, each one is separately connected to the +ve and -ve terminals by being connected to the main circuit at each end of the component's terminals.

If you have two cells producing the same p.d. wired in parallel, the p.d. of the circuit is just the same as one cell.

The two symbols for an electricity supply.

 Direct current (d.c. or dc) means the current only flows in one direction and the convention current flows from positive (+) to negative (-). Electrons actually flow in the opposite direction!

  Alternating current (a.c. or ac) switches direction in a continuous oscillation e.g. 50 Hz i.e. changing direction 50 times a second.

circuit symbol for a resistor, which resists the flow of an electrical current e.g. in a component, often a thinner wire than the rest of the circuit wire.

or are circuit symbols for a variable resistor.

It behaves like any other resistor, BUT, the resistance can be varied e.g. by turning a mechanical slider like in a dimmer switch for a lamp in a room.

The more of the thin resistance wire the current goes through, the greater its resistance and the smaller the current.

In the school laboratory you may come across it as a rheostat by which you can alter the resistance by moving a slider along a resistance wire.

circuit symbol for a filament single lamp bulb.

circuit symbols for two lamp bulbs wired in series.

circuit symbols for two lamp bulbs wired in parallel.

circuit symbol for a voltmeter that measures the potential difference in volts (p.d. in V).

The voltmeter is always wired in parallel across another circuit component to measure the p.d. in volts across it.

circuit symbol for an ammeter, an instrument that measures the flow of electrical current in amps (A).

This may be wired in series or parallel depending on which part of a circuit you want to know the current flow.

circuit symbol for a fuse. This melts and breaks the circuit if the current increases above a safe limit.

circuit symbol for a diode, sometimes the symbol is enclosed in a circle

A diode only allows a current to flow in one direction.

circuit symbol for a thermistor whose resistance changes with temperature i.e. the current allowed to flow varies with temperature.

circuit symbol for a light emitting diode (an LED), a semiconductor device that changes electrical energy into light energy i.e. it glows when a potential difference (voltage) is applied across it.

It is a much more efficient device than a hot filament lamp bulb.

circuit symbol for a light dependant resistor (LDR), sometimes the rectangle is enclosed in a circle

The resistance of an LDR changes depending on the intensity of light that shines on it.

The greater the light intensity, the lower the resistance and the greater the current flow.

circuit symbol for an electric motor, sometimes its just a circle with an M in it


Circuit symbols (as far as I know) NOT needed for UK GCSE physics courses ???

circuit symbol for capacitor, a device that stores energy in the form of electrically charged field between its plates.

circuit symbol for microphone, that converts a sound wave into an electrical signal.

circuit symbol for loudspeaker, that converts an electrical energy signal into sound energy.

circuit symbol for a transformer, which converts an a.c. current of one voltage in one input coil into an a.c. current of a different voltage in a second output coil.

circuit symbol for a bell.

circuit symbol for a buzzer.


Lots of electrical (electronic) circuit symbols - how many can you identify?

symbolsQ.gif

sym01

wire

sym02

T junction

sym03

2 or more cells wired in series

sym04

simple resistor

sym05

variable resistor

sym06

bulb or lamp

sym07

ammeter to measure current

sym08

closed switch (on)

sym09

open switch (off)

sym10

a single cell (battery)

sym11

2 cells wired in series

sym12

3 cells in series

sym13

fuse wire

sym14

2-way switch

sym15

diode

sym16

light emitting diode (LED)

sym17

variable resistor potentiometer

sym18

capacitor

sym19

electric motor

sym20

microphone

sym21

light dependent resistor (LDR)

sym22

speaker

sym23

transformer

sym24

thermistor

sym25

bell

sym26

buzzer

sym27

voltmeter for measuring p.d.

sym28

2 cells wired in parallel

sym29

2 lamps in parallel

sym30

2 lamps in series

INDEX of notes on drawing and interpreting simple electrical circuits


Keywords, phrases and learning objectives for circuit symbols in electrical circuits

You must be able to know a variety of electrical circuit symbols i.e. the  symbolism used in drawing and constructing circuit diagrams.

Know how to read circuit symbols in the context of understanding how to read an electric circuit and how it works.


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