Components
and Circuit Symbols To learn these symbols, use the "LOOK, COVER, WRITE, CHECK" method. (It is fun to work in pairs when you are doing this.) 1, LOOK
at the component and its symbol and try to remember it.
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Component
Name
|
Type |
Examples
|
Circuit
Symbol
|
What
it does
|
Battery | general |
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Provides the e.m.f. or power to push current around an electrical/ electronic circuit. |
Unconnected Crossing Wires |
general |
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Shows
where wires or conductors cross but do not make electrical contact. |
Connected
Wires or Junction |
general |
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The darkened electrical tracks allow current to branch off, or flow, into a different part of the circuit.The current entering a juction equals the current(s) leaving the junction. |
Push to Make Switch | input |
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Allows current to flow through it when it is pushed. It is normally OFF. (Available in many colours.) |
Push to Break Switch | input |
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Stops current flowing through it when it is pushed. It is normally ON, allowing current to flow. (Available in many colours.) |
Reed Switch | input | ![]() |
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When a magnet is brought close to the case of the glass/plastic reed switch, contacts inside it close. The current can now flow through it. |
Tilt Switch | input |
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When the metal case is tilted from side to side, a contact inside is made to close and open according to the angle of the switch. |
Micro S.P.D.T. Switch | input |
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SPDT:Single Pole Double Throw. A lever operated switch that can connect its input (pole) to one of two outputs (throws). |
Push S.P.D.T Switch | input |
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SPDT:Single Pole Double Throw. A push operated switch that can connect its input (pole) to one of two outputs (throws). |
LED (Light emitting diode) | output |
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A coloured indicator that lights to show something has turned on or happened. It generally needs a protecting resistor. Also available in clear higher power types that can be used to illuminate or see with. |
Lamp or Bulb | output |
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Produces clear omni-directional light that can be used to see with or show that something is switched on. |
Buzzer | output |
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Emits an audible warning tone. |
Motor | output |
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Rotates very quickly and is usually slowed down with external gears, to provide greater torque (rotational force) when making things move. |
Transistor
(npn type) |
controller |
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Often used as an electronic switch to turn on lower-powered output devices such as LEDs. lamps etc. It is triggered by a small voltage applied to its input (base). |
Integrated Circuit |
controller |
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These can contain many thousands/millions of electronic components housed on a square cm. wafer of silicon. A microprocessor is a larger scale version of this 8 pin d.i.l. (dual in line) device. (Note Pin 1 is shown by the black dot on the case). |
Fixed Resistor |
general |
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Used
to control current/ voltage in a circuit. Its fixed resisance is measured
in Ohms (
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Variable Resistor |
general |
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Adjustable
resistor - used to vary the current/ voltage in a circuit. It is measured
in Ohms (
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Light
Dependent Resistor |
input |
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Varies
its resistance as the light falling on it changes. |
Thermistor | input |
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Varies
its resistance as its temperature changes. |
Non
- Polarised or
Non - Electrolytic Capacitor |
general |
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Used to store electrical charge. Often combined with resistors to make timing circuits or used on their own to remove "noise" or interference in a circuit. |
Polarised
or Electrolytic Capacitor |
general |
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Used to store electrical charge. They can also be combined with resistors to make timing circuits. They have polarity (+ / -) and must be connected the right way round in a circuit. Note the blue negative stripe shows the minus (-) side. |
Voltmeter (multimeter - in example set to read voltage up to 20v) |
general |
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Measures the voltage or potential difference across two points of an electrical/electronic circuit. Connect in parallel. |
Ammeter (multimeter - in example set to read current up to 200mA) |
general |
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Measures the current flowing through a circuit/ wire or component. Connect in series. |
When
You Are Ready...
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