Circuit components
What are circuit symbols?
- The diagram below shows the circuit symbols that could be used in circuit diagrams to represent circuit components
- You will be expected to know what each component is and how it behaves in a circuit
Circuit symbols represent these components in circuit diagrams
Types of circuit components
Power supplies
- Cells, batteries, power supplies and generators all supply current to the circuit
Resistors
- Potential dividers, fixed and variable resistors, thermistors and light-dependent resistors (LDRs) are all used to control current
Meters
- Ammeters and voltmeters are used to measure the current and potential difference
- Ammeters are always connected in series whilst voltmeters are always connected in parallel
Switches and functional components
- Switches open and close a circuit and determine whether current can flow
- Functional components perform specific roles when current passes through them:
- Motors rotate
- Lamps emit light
- Heaters transfer thermal energy
- Bells emit a sound
Electromagnetic components
- Magnetising coils, relays and transformers use electromagnetic effects
- Relays use a small current in one circuit to switch on a much larger current in another
- Transformers 'step up' and 'step down' current and potential difference
Fuses
- Protect expensive components from current surges and act as a safety measure against fire
Thermistors
- A thermistor is a non-ohmic conductor and a temperature-dependent resistor
- The resistance of a thermistor changes depending on its temperature
- As the temperature increases the resistance of a thermistor decreases and vice versa
The resistance through a thermistor is dependent on the temperature of it
Light-dependent resistors
- A light-dependent resistor (LDR) is a non-ohmic conductor and sensory resistor
- Its resistance automatically changes depending on the light energy falling onto it (illumination)
- As the light intensity increases, the resistance of an LDR decreases
Resistance of an LDR depends on the light intensity falling on it
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