# Electric circuits and fields > resistance

An approach to Ohm's law in a quick demonstration.

Determining resistance from measurements of potential difference (p.d.) and current.

Investigating the changing resistance of a wire as it heats up.

Introduces the idea of a variable resistor, or rheostat.

A simple investigation of the factors affecting the resistance of a wire.

This activity models an archaeological survey (as students in the UK might have seen in TV programmes such as Time Team).

They learn that the resistance between two points depends on the shape and resistivity of the material(s) with which they are in electrical contact.

This activity models a railway track-circuit signalling system. Train wheels and axles provide an electrical connection between the two rails on which they travel. This enables a track signalling circuit to detect the presence of a train on a given section of track.

Students use their existing knowledge of resistors combining in parallel, and of internal resistance, to explain its operation.

An example of the characteristics of a simple component, giving students opportunities to construct a circuit, gather data and perform some analysis.