1. Warm-up Why do loops of wire in a motor rotate?
What is similar between Electric motor, and Electric meter?
What is electromagnetic induction?
Name 4 objects that apply electromagnetic induction.

2. Chapter 37: Electromagnetic Induction
Faraday discovered:
Magnetic and Electric fields interact to produce a Force.
(3rd right hand rule)
Magnetism can produce electric current in a wire!!
How so?
Michael Faraday

3. Electromagnetic Induction
The phenomenon of inducing voltage in a conductor by changing the magnetic field near a conductor is known as Electromagnetic Induction
Magnetic field changes when either the magnet or the coil moves or when they both move.

4. Faradays experiment
Molecular Expressions: Electricity and Magnetism - Interactive Java Tutorials: Faraday's Magnetic Field Induction Experiment

5. Induced Voltage?
why is the phrase Induced voltage used instead of induced current?
Answer:
In order for current to flow between two points of a conductor, there must be a difference of potential between those points. That potential difference is the voltage. Therefore, Voltage is induced first in order for current to flow.

6. Electromagnetic induction
video

7. Magnitude of the induced voltage
What factors affect the magnitude of the induced voltage?
Answer:
The rate (R) at which Flux (magnetic field) is changing,
The number of coils/turns (N) of the conductor

8. The Faradays law.
Induced voltage (V) in a coil is proportional to the product of;
the rate (r) at which the magnetic field changes within the loops, and
Number (n) of loops (turns /coils)

9. Question;
Why is it hard to move the magnet into the coil if the coil has many loops?

10. Lenz’s Law The law notes that;
an induced voltage always produces a magnetic field that opposes the field that originally produced it.

11. Lenz’s law

12. Application of electromagnetism
Generator
The coil is rotated mechanically using one’s hand,
Other ways of rotating the coil include
Water-hydro power
Wind- wind mills
Steam-
Geothermal,
Nuclear Reactors

13. application Name 4 objects that apply electromagnetic induction.
Transformer
Generator
Motor
Electro magnet

14. Homework
Textbook pg 592 # 1-10

15. The transformers

16. A simple transformer
A simple transformer is a set of induction coils as shown below.
Primary coil induces voltage onto the secondary coil

17. Primary and secondary coils
A common transformer is made up of an iron core and two coils of wires as shown below.
The Primary coil is connected to the power source.
The secondary coil gets induced with current.

18. What does it do?
Molecular Expressions: Electricity and Magnetism - Interactive Java Tutorials: Transformer

19. Induction process (Mutual induction)
Happens when current in the primary is changing (increasing or decreasing).
Changing current induces a magnetic field that is changing continuously on the core, a condition necessary for induction of voltage continuously on to the secondary coil.
When current is not changing (increasing or decreasing), there is no induction taking place.

20. Why is the AC preferred to DC?
We can increase and decrease current flow by opening and closing (Switching off and on) the circuit continuously when using a DC current, or just use AC current. The Ac is changing continuously

21. Why is an Iron core preferred to two coils apart?
Answer:
Iron core concentrates the magnetic field within itself by forming loops that get into contact with the secondary coil. These loops of magnetic field induce voltage in the secondary coil.

22. Step up Transformers
The number of coils in the secondary and primary determines whether a transformer is a step up or step down transformer.
less number of coils in primary
more number of coils in secondary

23. Step down Transformers
Notice that power transferred is the same.
More number of turns in primary coil
Less number of turns in secondary

24. What is the relationship between primary voltage, secondary voltage and the number of turns?
Answer:

25. The relationship between in-put and out-put power is:
Power input = power output.

26. Class work & Homework Textbook Page 592, # 11-15
Hm WK Textbook page 594, # 34-42