Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Flowing fluids can become charged


To illustrate the dangers associated with transferring fuel.

Apparatus and materials

Small polythene funnel

50 cm polythene tubing

50 cm of copper tubing

polystyrene beads (e.g. as used in bean bags)

Small beaker

Small calorimeter can

Coulombmeter or gold leaf electroscope

Clamp stand 

Health & Safety and Technical notes

Read our standard health & safety guidance

There is a risk of slipping if the spheres fall onto the floor. 

If possible stand the whole apparatus on a tray to contain any spilled polystyrene spheres.


Apparatus set-upa Assemble the apparatus as in the diagram:

  • place the calorimeter on top of the coulombmeter or electroscope 
  • clamp the tube and funnel above the calorimeter with the end of the tube just at the centre of the calorimeter. 

b Pour polystyrene spheres into the funnel so they flow down into the calorimeter.

c The charge on the spheres will cause the gold leaf to rise, or produce a reading on the coulombmeter.


Teaching notes

1 The polystyrene spheres, which are insulators, become charged by friction as they tumble down the insulating tubing. It is important that this tubing is polythene and not PVC. This illustrates how insulating liquids such as aviation fuel can become charged as they flow through pipes. 

2 Repeat the demonstration with copper tubing connected to the calorimeter, to show that any charge developed is now safely discharged.

This experiment was submitted by Sylvia Bell, Head of Physics at Nottingham High School for Girls.


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