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Electricity and Magnetism
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Worksheet 1 The man who lit up the world
Time to Think (p. 9)
1.
This invention makes it possible to change electrical energy to light energy in a
practical way, thus producing a convenient, bright and safe light source from
electricity.
2.
Edison thought that a practical light bulb should have a wire of high resistance
because a wire of high resistance will convert more electrical energy into heat.
When the wire is very hot, it glows and emits light.
3.
Edison filled the light bulb with nitrogen gas so that the light bulb had no
oxygen inside to prevent the wire inside the bulb from burning.
4.
This protects the interest of the inventor for a period of time during which only
the inventor can make and sell the product of the invention.
5.
(Open ended answer) This statement is true in some cases in which hard work
is more important than bright ideas. Many of Edison’s inventions came from
hard work. But in some cases the reverse is true, e.g. the finding of the structure
of DNA by Watson and Crick.
6.
He thought that Edison often worked by trial and error. If he could design his
experiments based on some theory, he could have avoided doing many useless
experiments.
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Electricity and Magnetism
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Worksheet 2 The man who captured lightning
Time to Think (p. 15)
1.
In both cases, there is an emission of light and heat through the air.
2.
Franklin hypothesized that lightning occurred when electrical charges jumped
from one cloud to the other.
3.
In the kite experiment, he wanted to find out whether the clouds carried
charges. His results showed that he succeeded in collecting the charges in the
clouds with Leyden jars.
4.
Based on his finding of lightning, he invented the lightning rod which
protected tall buildings and structures from being struck and damaged by
lightning.
5.
When performing the kite experiment, one should avoid any direct contacts
with the parts that carried the charges from the clouds, such as the wet string
and the metal key to prevent from electric shocks.
6.
Students may collect charges from different clouds with Leyden jars and show
that some clouds have positive charges and some have negative charges.
7.
The charges in the clouds are discharged to the lightning rod, which conducts
the charges along a wire to the ground instead of through the building.
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Electricity and Magnetism
Answers
Worksheet 3 The person who invented the first dynamo
Time to Think (p. 21)
1.
Faraday learnt science by reading the books he was given to bind, such as
Encyclopedia Britannica and attending meetings of the City Philosophical
Society and lectures of the Royal Institution to learn about the latest advances in
science.
2.
When Faraday heard that Ampère had used an electric current to turn iron
inside a coil of wire into a magnet, Faraday thought that a magnet could cause
an electric current to flow.
3.
Faraday placed coils of wire near magnets in various ways to see whether an
electric current could be generated in the wire.
4.
When a current started to flow in the first coil, the magnetic field around the
second coil suddenly increased as the iron ring became a magnet.
5.
The transient current was generated by a change in magnetic force on the wire
of the second coil.
6.
When a steady current flowed in the first coil, there was no change in magnetic
force on the wire of the second coil, hence no current is detected in the second
coil.
7.
When a bar magnet is moved in and out of a coil, there is a change in magnetic
force on the wire of the coil, hence inducing a current to flow.
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Electricity and Magnetism
Answers
8.
Students design their own dynamo. Example: a bicycle dynamo
(Students should include materials, clear procedure and data and results
obtained in operating the dynamo.)
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