Electrical Components (T2) Flashcards
What are fixed resistors used for?
They are included in circuits in order to control the sizes of currents and voltages.
What is a thermistor and how do they work?
A thermistor is a resistor whose resistance changes dramatically with temperature.
They are made from semiconducting material such as silicon or germanium.
At room temperature the number of free electrons is small so the resistance is large.
If warmed the number of free electrons increases and its resistance decreases.
Name two applications that thermistors are used in..
- fire alarms
- thermostats
What is an LDR and how do they work?
A Light Dependent Resistor.
In dark conditions they have few free electrons so have a high resistance.
If light is shone onto an LDR then more electrons are freed and resistance decreases.
What kind of applications would an LDR be used for?
LDR’s are often used in light sensitive circuits in devices such as…
- photographic equipment
- automatic lighting controls
- burglar alarms
What is a diode and how do they work?
Diodes are special resistors that behave like one way valves.
When current flows through them in one direction there is little resistance, but if the current tries to flow in the opposite direction the resistance is high.
When are diodes used?
In circuits where it is important for current to flow only in one direction, such as rectifying circuits that convert alternating current into direct current.
What is an LED?
A Light Emitting Diode.
A diode that glows when a current is flowing through it.
