Diodes, LDRs & Thermistors
Applied Science: BTEC Level 3 National Extended Diploma, topic 3.7.2
Diodes
A diode is a component that only allows current to flow through it in one direction.
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Diodes
- A diode is a component that only allows current to flow through it in one direction.
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Rectifiers
- A rectifier is a component that turns an alternating current (repeatedly changes direction) into a direct current (one direction).
- Diodes act as rectifiers as they block the alternating current when it changes direction.
Thermistors and LDRs
Thermistors and LDRs are devices where resistance changes with temperature or light. They can be used as switches for heaters and lights.
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Thermistors
- A thermistor is a component where resistance changes with its temperature.
- Usually, increasing temperature decreases the resistance.
- We can use a thermistor to turn a heater off when a house reaches certain temperatures.
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LDRs
- A light dependent resistor (LDR)s resistance changes with light intensity.
- Usually, increasing light intensity decreases the resistance.
- We can use LDRs to switch lights on when it gets dark or to know whether or not a camera phone needs to use “flash”.
Test yourself on Diodes, LDRs & Thermistors
Which of these can a diode not do?
If a thermistor is connected in series with a resistor and battery, what will happen in the circuit when the temperature increases?
What effect will increased light intensity have on an LDR?