Electromagnetic Induction Flashcards
What happens when an electrical conductor moves relative to a magnetic field?
Avoltage (potential difference) is
induced across the conductor
What happens to an electrical conductor when there
is a change to the magnetic field that it is placed in?
The voltage (potential difference) is also changed
How do you produce an electric current using a
magnet and a conductor on a small-scale?
● Moving a coil of wire between magnetic poles
● Moving a magnet within a coil of wire
Once a voltage is induced, if there is a complete
circuit, a current will also be induced.
How is electrical current produced on a large-scale?
An electromagnet is rotated around a
coil
What factors affect the size of an induced voltage?
● The number of turns on the coil of wire
● How strong the magnetic field is
● The speed of the movement
What is the requirement for an induced potential
difference to cause a current flow?
The conductor must form a closed loop
or be part of a complete circuit
What can be said about the direction of the magnetic
field produced by an induced current?
● The direction of the field is such that it
opposes the change that induced the
current
● This change is either the movement of the
conductor or a change to the field
What are two ways that the generator effect is used
to generate different types of current?
● In an alternator to produce
alternating-current
● In a dynamo to produce direct-current
How does a dynamo generate current?
A coil of wire rotates inside a magnetic
field. A commutator is used to ensure it continues rotating in the same direction,
therefore keeping the current flowing in the same direction (d.c. current).
How is electromagnetic induction used in alternators
to generate alternating current?
A coil of wire rotates in a magnetic field.
The end of this coil is connected to slip
rings which will cause the current to
change direction while rotating. This means
a.c is produced.
What electromagnetic effect does a microphone take
advantage of and how?
● The generator effect
● It converts the pressure variations in
sound waves into alternating current
How do loudspeakers make use of the motor effect?
The motor effect is used to convert
variations in the current of an electrical
circuit into the pressure variations which
produce audible sound
Explain how a loudspeaker works
● Acone wrapped in wire is connected to an a.c power
supply and is placed in a permanent magnetic field
● When current flows through the wire, it creates a
magnetic field which interacts with the permanent field
● This produces a force which causes the cone to
vibrate, producing sound
How is the pitch of the sound from a loudspeaker
changed?
● The frequency of the a.c current is
altered
● This creates a different frequency of
vibration in the cone
How do microwaves convert sound into electrical signals?
● Sound produces pressure variations which cause the
diaphragm to vibrate
● Acoil of wire is connected to the diaphragm, so as the
diaphragm moves, the coil also moves
● Movement in a magnetic field = a p.d. is induced
● As there is a complete circuit a current is also created
