Electric Kettle

Explore the relationship between resistance and temperature
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

 

The diagram shows a simple circuit: the cell provides energy, V volts, which causes a current, I amps, to flow around the circuit. There is also a resistance, R ohms.

 

Image
Electric Kettle


 

This circuit provides a simple model for what happens in an electric kettle: a resistance converts electrical energy into heat energy by impeding the flow of electrons around the circuit.

The table shows data collected from a circuit like this.

 

 

Resistance (ohms) Temperature (degrees Celsius)
5 44.9
6 50
7 55.1
8 59.9
9 65
10 70.1

 

 

  • Draw a graph of this data, with the resistance on the horizontal axis, putting a straight line through the points.
  • Find the gradient of the line.
  • Find the equation of the line.

 

 

 

 

Once you have found the equation, discuss these questions:

 

 

 

  • What resistance would you need to heat water to 100 C °?
  • What would the temperature be if the resistance was zero?
  • Do you think that in practice, any circuit can have zero resistance?