Summary Fill in the Blanks + Exam Practice
Click the blanks to reveal the key answers. Use the longer-answer sections for full exam-style explanations. Diagram spaces have been left ready for your uploads.
1Definition of Electromagnetic Induction
Electromagnetic induction happens when a
_______conductor
cuts a magnetic
_______field
.
This causes an induced
_______e.m.f.
or an induced
_______current
.
Electromagnetic induction can also be described as a
_______changing magnetic field
in a coil producing an induced e.m.f.
If the conductor and magnetic field do not move relative to each other, there is
_______no induced e.m.f.
.
Diagram Upload Space 1
Insert your definition / basic induction diagram here, for example a magnet moving into a coil connected to a galvanometer.
2Inducing e.m.f. in a Coil
When a bar magnet is moved
_______into
a coil, the galvanometer needle deflects in one direction.
When the magnet is moved
_______out of
the coil, the galvanometer needle deflects in the
_______opposite
direction.
When the magnet is held
_______stationary
relative to the coil, the galvanometer shows
_______no deflection
.
This shows that induction depends on
_______change
in magnetic field, not just the presence of a magnet.
Diagram Upload Space 2
Insert your three-position coil and galvanometer diagram here: magnet moving in, moving out, and stationary.
3Increasing the Magnitude of the Induced e.m.f. and Current
The induced e.m.f. increases when the magnet is moved
_______faster
.
The induced e.m.f. also increases when a
_______stronger magnet
is used.
Increasing the number of
_______turns
in the coil increases the induced e.m.f.
For a straight wire, increasing the length of wire in the magnetic
_______field
increases the induced e.m.f.
A bigger induced e.m.f. usually causes a larger induced
_______current
if the circuit is complete.
Diagram Upload Space 3
Insert your diagram showing a moving wire between magnetic poles, or your notes diagram listing ways to increase induced e.m.f.
4Changing the Direction of the Induced e.m.f. and Current
The direction of the induced current reverses if the motion is reversed.
If a magnet was pushed
_______in
before, pulling it
_______out
reverses the current.
Reversing the magnet’s
_______poles
also reverses the direction of the induced e.m.f.
For a moving wire, moving the wire in the
_______opposite direction
reverses the induced current.
Turning the magnet around so that the poles are
_______reversed
also changes the direction of the induced current.
5Fleming’s Right-Hand Rule
Fleming’s Right-Hand Rule is used to find the direction of the induced
_______current
.
The first finger points in the direction of the magnetic
_______field
.
The thumb points in the direction of the
_______motion
of the conductor.
The second finger points in the direction of the induced
_______current
.
The conductor must move
_______perpendicular
to the magnetic field for maximum induction.
Diagram Upload Space 4
Insert your Fleming’s Right-Hand Rule diagram here.
6Lenz’s Law
Lenz’s Law states that the induced current flows in a direction that
_______opposes
the change that produced it.
If a magnet approaches a coil, the induced current produces a magnetic effect that tries to
_______oppose the approach
.
If the south pole approaches the coil, the near face of the coil becomes a
_______south pole
to repel it.
This means the induced current creates a magnetic field that resists the
_______change
.
Diagram Upload Space 5
Insert your Lenz’s Law polarity / coil-current diagram here.
Exam Practice – Click to Reveal Answers
Define electromagnetic induction.
Click to reveal answer
Electromagnetic induction is the production of an induced e.m.f. or current when a conductor cuts a magnetic field.
It can also be defined as the production of an induced e.m.f. when the magnetic field in a coil changes.
Explain what happens when a bar magnet is pushed into, pulled out of, and held stationary inside a coil connected to a galvanometer.
Click to reveal answer
When the magnet is pushed into the coil, the magnetic field through the coil changes and an e.m.f. is induced, so the galvanometer deflects in one direction.
When the magnet is pulled out, the change is in the opposite sense, so the induced e.m.f. and current reverse and the galvanometer deflects in the opposite direction.
When the magnet is held stationary, there is no change in magnetic field through the coil, so no e.m.f. is induced and the galvanometer returns to zero.
Describe three ways to increase the magnitude of the induced e.m.f. in a coil.
Click to reveal answer
Move the magnet faster.
Use a stronger magnet.
Increase the number of turns in the coil.
Describe two ways to change the direction of the induced current.
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Reverse the direction of motion, for example pull the magnet out instead of pushing it in.
Reverse the poles of the magnet by turning it around.
Explain how Fleming’s Right-Hand Rule is used to find the direction of induced current.
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Hold the right hand with the thumb, first finger and second finger at right angles to each other.
The first finger points in the direction of the magnetic field.
The thumb points in the direction of motion of the conductor.
The second finger then gives the direction of the induced current.
State Lenz’s Law and explain it using a magnet approaching a coil.
Click to reveal answer
Lenz’s Law states that the induced current flows in a direction that opposes the change that causes it.
If a magnet approaches a coil, the induced current in the coil produces a magnetic field that opposes the approach.
For example, if the south pole approaches, the near end of the coil becomes a south pole so that it repels the approaching magnet.
Explain why no current is induced when the magnet is held still inside the coil.
Click to reveal answer
No current is induced because the magnetic field through the coil is not changing.
Electromagnetic induction requires a change in magnetic flux / changing magnetic field.
Exam Summary
Electromagnetic induction is the production of an induced e.m.f. when a conductor cuts a magnetic field, or when the magnetic field through a coil changes.
Greater induced e.m.f. is produced by faster motion, a stronger magnet and more turns in the coil.
The direction of the induced current changes if the motion or magnetic poles are reversed.
Fleming’s Right-Hand Rule gives the direction of induced current.
Lenz’s Law states that the induced current opposes the change producing it.
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