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Chapter 21 Study Guide
Magnetism
Review the following vocabulary terms:
Electric generator
Alternating current
Aurora
Magnetic domain
Electromagnet
Transformer
Put the following steps in order to make an electric bell work:
Press the button _____
Hammer strikes the bell _____
Circuit closes _____
Electromagnet is turned off _____
Electromagnet attracts plate attached to hammer _____
Electromagnet is turned on _____
Spring pushes plate and hammer _____
Circuit closes _____
Circuit opens _____
Be able to answer the following questions:
1.) Explain how a transformer can change voltage.
2.) Compare motors and generators in terms of electrical and kinetic
energy.
3.) How are a magnetic field and a moving electrical charge related?
4.) What is the core of an electromagnet usually made of?
Memorize the following formula for transformers:
Input coils/output coils = input voltage/ output voltage
For example, a transformer has an input voltage of 5,000 V and 1,000
coils of wire on the input side. If the output voltage is 1,250 V, how
many coils of wire are on the output side?
Review the following facts:
 The domains in an unmagnetized material that can be magnetized
are aligned in all directions.
 The strength of an electromagnet cannot be increased by reversing
the current.
 Moving a magnet in and out of a coil of wire produces an electric
current.
 If both coils of a transformer have the same number of turns, the
output voltage will be the same compared to the input voltage.
 A magnetic field exists around a wire whenever current flows
through the wire.
Know how to build:
1.) Electromagnet
2.) Motor
3.) Magnetize an object