This document discusses electromagnetic induction, including the motor and generator effects. It provides explanations and examples of how current flowing in a wire creates a magnetic field (motor effect), and how a changing magnetic field induces current in a conductor (generator effect). Right-hand rules are introduced to predict the direction of forces and currents. Examples are given for determining the direction of force on current-carrying wires and moving charges in magnetic fields.

1. Electromagnetic
Induction
The interaction between current and
magnetic field

2. Remember from Year 12
The relationship between electricity and magnetism (Motor
effect)
• When current flows through a wire a
magnetic field is created around the wire
• And if the wire is coiled (to form a solenoid)
Just like;

3. Magnetic Fields

4. Remember from Year 12
The relationship between magnetism and electricity
(Generator effect)
• When a wire moves through a magnetic
field a voltage is induced
• Or a magnetic field moves through a coil a
voltage is induced

5. Using Your Hand and Formulae
• Right-hand grip rules
• Right –hand slap rule
• Force on a current carrying wire (motor effect)
F BIL(sinθ)
• Induced voltage (generator effect)
V BvL
• Force on a charge
F Bqv(sinθ)

6. The Motor Effect
• A current carrying wire at an angle to a
magnetic field experiences a force
• This is as a result of the interaction
between the magnetic field and the
magnetic field around the wire.

7. Electric Motors
• Most electric motors
use electricity to
make magnetism
-the motor effect
The use of electric
motors is widespread
with most of us using
many each day

8. RH Grip Rule -Wire

9. RH Grip Rule -Solenoid

10. RH Grip Rule -Solenoid
Predict the direction of the North magnetic pole

11. RH Grip Rule -Solenoid
Predict the direction of the North magnetic pole

12. RH Grip Rule -Solenoid
Predict the direction of the North magnetic pole

13. RH Grip Rule -Solenoid
Predict the direction of the North magnetic pole

14. RH Motor Rule Examples
I
I
Predict the direction of the force on the wire and
label the positive end of the wire

15. RH Motor Rule Examples
Predict the direction of the force on the wire and
I
I
label the positive end of the wire

16. RH Motor Rule Examples
Predict the direction of the force on the wire and
I
I
label the positive end of the wire

17. RH Motor Rule Examples
Predict the direction of the force on the wire and
label the positive end of the wire

18. RH Motor Rule Examples
Predict the direction of the forces on the wire coil
at 1 and 2

19. Force on a Charge
• A single charge or a charged object will
also experience a force as it moves
through a magnetic field as it too creates a
magnetic field as it moves (just like current
in a wire)

20. Force on a Charge

21. Slap Rule for Force on a Charge
v
v

22. Force on a Charge

24. Force on a Charge
Predict the direction of the force on the moving
positive charge
+
q

25. Force on a Charge
Predict the direction of the force on the moving
positive charge
+

26. Force on a Charge
Predict the direction of the force on the moving
negative charge
-q

27. Force on a Charge
Predict the direction of the force on the moving
negative charge
-

28. Force on a Charge –the maths
• Force on moving charges in a wire;
F BIL(sinθ)
• Force on moving charges on their own;
F  Bqv(sin )
Where;
F=force (N)
B= magnetic field strength (T)
q=charge on the object (C)
v=velocity of the charge (ms-1)
=angle from field lines ()

29. Exercises
1. Find the force on an electron (1.60×10-19C)
travelling at 3×107 ms-1 perpendicular to a
magnetic field of 0.18T
9×10-13N
2. Calculate the charge of a particle travelling
at 340ms-1 perpendicular to a 1.2T
magnetic field that experiences a force of
3.5×10-12N
8.6×10-15C

30. Electricity Generation
• Most generators use
magnetism to
generate electricity
-The generator effect

31. Induction -the Generator Effect
• A wire that moves through a magnetic field
has a voltage induced across it and
therefore a current is induced
• Of course the magnetic field can move past
the wire and cause induction also
• Induction is the result of the interaction
between the magnetic field and the
negatively charged electrons in the wire

32. RH Generator Rule
•To predict the direction of
the induced current use the
modified RH slap rule
•As with the RH slap rule
for the motor effect, the
thumb is the cause (the
velocity of the wire for a
generator), the fingers are
the field lines, and the
“slap” is the direction of the
resultant (in this case the
current)
v
B
I

33. RH Generator Rule Examples
v
Predict the direction of the current and label the
+ve end of the wire

34. RH Generator Rule Examples
Predict the direction of the current and label the
v
v
+ve end of the wire

35. RH Generator Rule Examples
Predict the direction of the current and label the
v
v
+ve end of the wire