Circuit Devices Flashcards
Electricity (15 cards)
What does LDR stand for?
Light Dependent Resistor
LDRs are resistors whose resistance varies with light intensity.
How does the resistance of an LDR change in bright light?
The resistance falls.
What happens to the resistance of an LDR in darkness?
The resistance is highest.
List some applications of LDRs.
- Automatic lighting
- Outdoor lighting
- Burglar detectors
What is a thermistor?
A temperature dependent resistor.
How does the resistance of a thermistor change in hot conditions?
The resistance drops.
What happens to the resistance of a thermistor in cool conditions?
The resistance goes up.
Provide examples of where thermistors are used.
- Car engine temperature sensors
- Electronic thermostats
What can sensing circuits do?
They can turn on or increase power to components depending on conditions.
What is the function of the fixed resistor and fan in a sensing circuit?
They always have the same potential difference across them because they are connected in parallel.
How is the potential difference (pd) shared in a circuit with a thermistor?
It is shared according to their resistances; the bigger a component’s resistance, the more pd it takes.
What happens to the resistance of the thermistor as the room gets hotter?
The resistance decreases.
What effect does the decrease in thermistor resistance have on the fan’s power?
The pd across the fixed resistor and the fan rises, making the fan go faster.
Fill in the blank: If you connect a bulb in parallel to an LDR, the pd across both the LDR and the bulb will be high when it’s _______.
dark.
What happens to the brightness of a bulb connected across an LDR as the room gets darker?
The bulb gets brighter.
