| Energy & Forces - Conversion & transfer of energy - Electricity - G13 |
  Teacher's
Guide
EF-C2.extra |
ISE 5-14 Curriculum Support Materials Overview advice |
| 1. Working with static electricity is not always predictable. Demonstrations of the effects of static tend to work better in dry conditions and so try to choose a dry day and work in the morning before the vapour level in the class builds up. |
 2.
To show the children the effects of static do some simple demonstrations.
Firstly take a plastic comb or ruler (these are better options than an acetate
or polythene rod) and rub it vigorously about 10 times with a clean, dry cloth (
a yellow duster is ideal). You will now be able to pick up small pieces of
tissue paper with the comb.
Rub a ruler or comb again with the dry cloth and this time turn on a cold tap so that there is a steady gentle stream running. Hold the charged ruler close to the stream and you should see the stream of water bend as it passes the ruler. (Practice this before trying to show the class.)
A nice variation of this is to make the ruler a fishing rod and
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Static
Electricity
We are all used to electricity from the mains and from batteries. This type of electricity flows and is called ‘current’ electricity. There is another type called ‘static’ electricity which stays in one place. Static electricity happens when two things are rubbed together so that one thing rubs off tiny parts of the atoms of the other thing. These tiny parts are called electrons. The item with the extra electrons will now be pulled to anything which is short of electrons but will be pushed away from anything which has too many electrons. so when you rub a balloon against a jumper, the balloon picks up some extra electrons from the wool. It will now stick to anything which has a need of electrons but will push away from another rubbed balloon which also has too many electrons.
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3. The children will all be
familiar with thunder and lightning and this is a good opportunity to talk about
thunderstorms, how lightning can hit the ground and how to count the time
between a lightning flash and the sound to see how many miles away the storm is.
Some safety aspects should be mentioned - never shelter under a tree in a
thunderstorm - try to get into a building or stay in a car and so long as you
are completely within the car, you should remain unharmed in the event of a
direct hit.
In the classroom we cannot make lightning but can make a tiny spark. |
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Making a Spark
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Lightning
Thunder and lightning are caused by static electricity. Clouds become charged as the tiny ice crystals inside them rub against each other. A cloud can get so charged up that electrons jump between it and the ground, or another cloud. This causes a huge spark which is lightning. Sometimes the spark will jump to another cloud and sometimes it will jump to Earth. The noise of lightning which we call ‘thunder’ is caused by the spark ripping through the air. Because light travels very much faster than sound we see the lightning before we hear the thunder. The time between the two depends on how far away we are from the spark. |
An
enjoyable demonstration which the children can repeat themselves, is easily done
using a small cake tin, a metal teaspoon, a lump of plasticine and a black bin
bag. Sellotape the bag out flat on the table and make the plasticine into a
handle on the inside of the tin. Hold the tin using the plasticine handle and
rub it around in a circle about ten times on the bin bag. Lift it off the bag
and hold the teaspoon very close to the tin and a tiny spark should jump across
from the tin to the teaspoon. Again this will work better some days than others
but it makes a tiny crackle as it jumps and the children will have to be very
quiet to try and hear it! It might be seen better in a darkened room and may
work better with an acetate sheet rather than a bin bag.
