9.6/8/9 Diodes, thermistors and LDRs Flashcards
What are diodes?
Diodes are semiconductors that only allow current in one direction. Diodes have two terminals: one direction has low (ideally zero) resistance and the other has high (ideally infinite) resistance.
What must you do when hooking an LED to a circuit and why?
When adding an LED to a circuit, a resistor must be added in series to the LED, otherwise the LED would take in a large current, becoming very bright for a short while then burn out, breaking the component.
What are thermistors?
A thermistor is an electrical component made from a semiconductor with a negative temperature coefficient. As the temperature of the thermistor increases, its resistance drops. The change in resistance is often dramatic. Resistance is inversely proportional to temperature.
What are thermistors used in?
Thermistors are used in temperature sensing circuits. A small change in temperature can be detected by monitoring the resistance of a thermistor:
*simple thermometers
*in thermostats to control heating and a.c. units
*to monitor the temperature of components inside of electrical devices (e.g. computers, phones, etc.) so that they can power down before overheating damages them
*to measure temperature in a wide variety of electrical devices (e.g. toasters, kettles, fridges, etc.)
*to monitor engine temperatures to ensure that the engine does not overheat
What are LDRs?
An LDR or light dependent resistor is a type of diode (made of semiconductor) that are small electrical components that change their resistance depending on light intensity. Resistance is inversely proportional to light intensity.
What are LDRs used in?
LDRs may be used in sports, automatic street lights, smartphones, laptops and space telescopes.
