P6 - Potential Dividers, LDRs & Thermistors Flashcards
What is teh relative resistance rule?
• Voltages across a pair of resistors is “shared out” according to their relative resistances, the rule is:
- The larger the share of the total resistance, the larger the share of total voltage..
What happens if the resistances are equal?
If the resistances are equal, each resistor takes half the voltage.
What happens if the top resistor has 80% of the total resistance?
It will take 80% of the total voltage.
How can the output be varied?
The output can be varied by swapping out one of the resistors for a variable resistor.
What do potential dividers allow?
Potential dividers allow you to run a device that requires a certain voltage from a battery of a different voltage.
What is the formula to work out the output voltage?
Vout = Vin x ( (R2/R1+R2).
Where do light dependent resistors have high resistance and low resistance?
- In bright light the resistance falls
* In darkness the resistance is highest.
What are some practical applications of light dependent resistors?
• They can be used in electronic circuits e.g. Automatic night lights, and burglar detectors.
Where do Thermistors have high resistance & low resistance?
- In hot conditions the resistance drops
* In cool conditions the resistance goes up.
What are some practical applications of thermistors?
• Thermistors make useful temperature sensors, e.g. Car engine temperature gauges, electronic thermostats.
How can you make a temperature sensor?
• Using a Thermistor and a fixed resistor in a potential divider, you can make a temperature sensor.
