Thermistors

Question 1

What is a thermistor?

Answer 1

• This is a resistor that varies resistance depending on the temperature.

Question 2

What happens to the resistance of a thermistor when you increase the temperature?

Answer 2

• The resistance decreases when you increase the temperature.

Question 3

If a component has a high resistance, what kind of potential difference would it have across it?

Answer 3

• High potential difference: more energy to push electrons along (current) , past metal ions in component.

Question 4

Explain how thermistors are used as a sensor in incubators.

Answer 4

• When thermistor is cool, the voltage across switch is high.
• A switch turns on and makes a sound at this particular voltage.

Question 5

Explain how thermistors are used in computers to avoid heating up.

Answer 5

• When thermistor is hot, the resistance decreases and the voltage is lower.
• This means the cooling fan takes “The greater share of voltage” to cool it down.

Question 6

What is the device that measures resistance directly?

Answer 6

• This is called an ohmeter

Question 7

Q: Trevoh gently heats the thermistor.
Describe and explain how heating the thermistor affects the brightness of the lamp.

Answer 7

• Heating thermistor decreases resistance
• This means the current in circuit is higher and bulb will shine brighter.

Question 8

True or False. If a thermistor is heated, the current in the circuit will remain the same.

Answer 8

• False.
• current will increase.
  Less resistance in circuit

Question 9

Explain how thermistors are used as sensors in heaters.

Answer 9

• Increase temp = decrease resistance in thermistor.
• Potential difference across thermistor decreases
• Potential difference across heater decreases and switches off.

Question 10

Why is the graph linking temperature and resistance curved?

Answer 10

• Because temperature and resistance aren’t directly proportional.
  As temperature increases, intervals get smaller and smaller

Question 11

What is the relationship between temperature and resistance in thermistor?

Answer 11

• As temperature increases, resistance decreases
• Non - linear relationship

Question 12

What happens to the overall current when temperature of thermistor decreases?

Answer 12

• Temperature down = resistance up
• Overall current decreases

Question 13

Q.)

Explain why the potential difference across the fixed resistor decreases as the temperature decreases.

Answer 13

• Temperature down = resistance up
• Thermistor gets higher share of P.D.
• Fixed resistor gets lower share.