The document discusses various topics relating to electromagnetic induction and effects. It explains that moving a wire through a magnetic field induces an electromotive force (EMF) in the wire, and that increasing the wire's speed, magnetic field strength, or length increases the induced EMF. It also describes Fleming's left-hand rule for induced currents, and how reversing the wire or magnet's direction reverses the current and EMF. Coils and generators are discussed as ways of inducing currents. Transformers, electromagnets, magnetic relays, circuit breakers, and electric motors are also summarized.

1. ELECTROMAGN
ETIC EFFECTS
IGCSE PHYSICS

2. Electromagnetic Induction
 A magnetic field can be used to produce
current.
When the wire is moved across the
magnetic field a small EMF(voltage) is
created. This is called electromagnetic
induction.
“EMF is induced”
Induced EMF increased by:
-Moving wire faster
-Using stronger magnet
-Increasing length of wire.

3. Induced Currents
Fleming’s right hand rule:
Difference between the left hand and the right hand
rule:
-When current causes motion the left hand rule
applies
The current and EMF
direction can be reversed
by:
• moving the wire in the
opposite direction
• turning the magnet
round so that the field
direction reversed.

4. How is Current Induced in
a Coil of Wire?
When a magnet is moved towards (or inside)
a coil of wire, a current is induced inside
the wire. This can be shown by connecting
the coil to a very sensitive ammeter called
a galvanometer.

5. The size of the induced current can be made bigger by:
1. Using a stronger magnet.
2. Moving the magnet at a faster speed.
3. Using more turns of wire on the coil.
These all result in the pointer on the galvanometer
moving further to the right.
The direction of the current can be reversed by:
1. Moving the magnet in the opposite direction.
2. Using a magnet facing the opposite way round
(with North becoming South).
These both result in the pointer on the galvanometer
moving to the left.
If the magnet stops moving, even though it may still be
inside the coil of wire, no current is induced in the wire.

7. Generators
 The coil rotates
 Magnetic fields are cut
 EMF is generated
 Causes current to flow
 Coil rotates– upwards,
downwards, upwards
causing the current to
flow backwards,
forwards, backwards.
Increasing EMF:
- Increasing the number of
turns on coil
- Increasing area of coil
- Use stronger magnet
- Rotate coil faster

8. Coils and Transformers
 Moving magnet induces EMF
 Magnetic field SAME effect.
 Mutual induction: when coils are magnetically
linked so that changing current in one coil
causes an induced EMF in the other.

9. Simple Transformer
- Alternating current
flows through primary
coil
- This sets up an altering
magnetic field in the
core.
- Coils of the secondary
coil ‘cut’ the altering
magnetic field thus
inducing an alternating
voltage in the output
coil.
Turns in output coil
=
Input voltage
output voltage
Turns on input coil

10. Step-up and Step-down
transformers
Step-up: this is when the
number of output coils is
greater than the number
of input coils which
means that there will be
a greater output voltage
as opposed to input
voltage.
Step-down: this is when the
number of output coils is less
than the number of input coils
which means that there will be
less output voltage as opposed
to input voltage.

11. Power Through a Transformer
= x Output
current
Output
voltage
Input
voltage
x Input
current

12. Magnetic Effects of Current
 When an electric current is passed through a
wire an magnetic field is produced. The
features of this magnetic field are:
 They are circles
 Field is strongest close to the wire
 Increasing current  increases strength of field.

13. Right-hand grip rule

14. Electromagnets
 These are types of magnets that can be
switched on and off.
Iron core
Coils
The strength of the magnetic field can be increased by:
- Increasing the current.
- Increasing the number of turns in the coil

15. Magnetic Relay
 When electricity is passed through the coil end
wires, it induced a magnetic field in the iron
ROD. This attracts the iron STRIP causing both
metal contacts to touch.
Metal
contacts.

16. Circuit Breaker
Circuit breaker- it is an
automatic switch cutting
off the current within a
circuit if it rises above a
specified value.
- In the case on the left, the
pull of the electromagnet
has become so strong that
it has attracted the soft iron
armature. This causes the
contacts to open and stop
the current.
- If u press the reset button,
the contacts close once
again.

17. Magnetic force on the current
 Copper is a non-magnet
 feels no force of the
magnet
But..
 If it has a current
passing through it, there
will obviously be a force
on the wire.
The wire moves ACROSS
the field. It is not
attracted to it.
Force is increased if:
-Current is increased
-Stronger magnet is used
-Length of wire in field is
increased.

18. Flemings Left Hand Rule

19.  A motor is made up from a coil
of wire which is positioned
between the two poles of the
magnet.
 When the current flows through
the coil, it creates a magnetic
field. This magnetic field that is
produced interacts with the
magnetic field produced by the
2 permanent magnets.
 The combination of these two
magnetic fields exert a force,
pushing the wire at right angles
An electric motor transfers electrical energy to
kinetic energy.
Improve turning

20. Increasing Turning Effect
 Increase the current
 Use a stronger magnet
 Increase the number of turns on the coil
 Increase the area of the coil.
Reversing the rotation
can be done by:
• reversing the battery
• reversing poles