10.6 Sensing circuits

Question 1

How can potential divider circuits be made useful?

Answer 1

Variations on potential divider circuits exist in that resistors can be swapped out for variable resistors, thermistors or LDRs. These can be placed in the circuit

Question 2

How can variable resistors be used in a potential divider circuit?

Answer 2

Variable resistors can be used to vary the output voltage in a circuit. The variable resistor has a maximum resistance of 2kΩ and a minimum of 0Ω. This means that the output voltage varies between 4.5V and 0V

Question 3

How can thermistors be used in a potential divider circuit?

Answer 3

A thermistor can be used in a potential divider circuit in a heating element. Thermistors have a high resistance at low temperatures, therefore the voltage will be high at 0°C and will switch the heater on. As the thermistor heats up the resistance decreases and will reach a minimum value of 50°C for example. This will turn the heater off. Data-loggers can be used if a continuous record of temperature is needed.

Question 4

What is a potentiometer?

Answer 4

A potentiometer works in the same way to a potential divider, but uses a length of resistance wire with a sliding contact.

Question 5

What are the advantages of using a potentiometer over a potential divider?

Answer 5

Potentiometers require less components to use in a circuit and they allow the full range Vin so Vout can range from 0V to Vin V.