STE 15080 Experiment Pack - Electrostatics
INTRODUCTION
This Experiment Pack provides a good range of equipment to carry out experiments and develop a good basic understanding of Electrostatics, together with 7 page Instructions and Teaching Guide.
Together with the highly recommended STE 10178 Van de Graaff Generator and STE 10181 Van de Graaff Generator Accessories, it will provide a complete laboratory for electrostatic investigations.
TOPICS COVERED
1. Electrification
2. Electrostatic induction
3. The gold-leaf electroscope
4. Detecting electricity
5. Determining the sign of a charge
6. Wimshurst’s frictional electric machine
7. The power of pointed conductors – the electric swivel
8. Jumping balls
9. The electric plume
EQUIPMENT
1 conical stand
1 clips with string
1 hooked support
1 candle with holder
1 plexiglas (acrylic) rod
2 PVC rods
2 60cm cables
1 gold-leaf electroscope
2 crocodile clips
1 Wimshurst frictional electric machine
1 universal support
1 pointed support
1 pointed conductor
1 electric swivel
1 jumping-ball experiment apparatus
2 polystyrene balls with string
1 electric plume
1 plastic container
EXAMPLE EXPERIMENT
(all worksheets have necessary diagrams)
7. THE POWER OF POINTED CONDUCTORS – THE ELECTRIC SWIVEL
The phenomenon known as “the power of pointed conductors” has great relevance in the field of electricity.
Pointed conductors have great ability both to gain and to lose electricity.
The American Benjamin Franklin applied this property to the lightning rod he invented, which is still to date the best method of protecting buildings from lightning.
This phenomenon can be interpreted physically as follows. When electric charges are transferred to a conductor, these will distribute themselves on its surface. If the conductor is spherical the charges’ distribution will be uniform. If not, the charges will gather up where the surface’s curvature is greater. If the conductor is pointed, this phenomenon will be greatly increased.
The density of the charge on the points is so high that a strong electric field is created around them. In the air, positive electrical charges are separated from the negative. In other words, the gases’ atoms lose some electrons, creating positive and negative ions.
Ions of opposite sign to that of the conductor are violently repelled, sometimes with striking visual effects.
Figure 10 shows how the charges repelled by a pointed conductor are able to blow out a candle.
Figure 11 shows the electric swivel: a conductor made of two points on a low-friction pivot. The device rotates due to the action and reaction principle.
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