Magnetism(Review)

1
Magnetism(Review)
2
Magnetic Field Lines always move out of the
__________end of a magnet!

1. East
2. North
3. South
4. West

3
Magnetic Field Lines always move into the
__________end of a magnet!

1. East
2. North
3. South
4. West

4
Where are all magnets the strongest?

1. At the North Pole
2. At the South Pole
3. At both Poles
4. Directly in the center

5
Magnets can be made of iron, _________, or nickel.

1. Copper
2. Carbon
3. Cobalt
4. Cadmium

6
Two similar poles of a bar magnet will always
_____________.

1. attract
2. repel

7
Two opposite poles of a bar magnet will always
_____________.

1. attract
2. repel

8
Electromagnetism

• --the relationship b/w electricity and magnetism

9
Is there a relationship between electricity and
magnetism? Lets see what I discovered!!!
Hans Christian Oersted
10
Oersteds Law

• The flow of electricity through a wire conductor
  produces a magnetic field around the wire.

11
Right Hand Rule

• The direction of the current determines the
  direction of the magnetic field.

12
Can anything affect the strength of a magnetic
field?
13
2 things affect the strength of a magnetic field

• Amount of current
• Increase current increase strength
• Decrease current decrease strength

• of coils of wire
• More turns of wire more strength
• Less turns of wire less strength

14
I was just wondering what would happen if I
slammed an iron core through a current carrying
coil of wire?
What did you find out?
15
If you take an iron core and insert it into a
coil of current carrying wire, you have a
temporary magnet called an electromagnet!!
16
Strength of an Electromagnet

• 2 things affect the strength of an
  electromagnet(same 2 things that affect the
  strength of a magnetic field)
• Amount of Current
• of turns of wire( of coils)

17
What happens to the strength of an electromagnet
if the current through the wire increases from 4
A to 9 A?

1. Remains the same
2. Increases
3. Decreases

18
Which electromagnet will be the strongest?
B
A
19
Uses of Electromagnets

• Electric Meters because of their ability to
  detect current(only work when there is one),
  electromagnets are used in a variety of electric
  meters.
• Ammetermeasures current
• Wired in series
• Voltmetermeasures voltage
• Wired in parallel
• Galvonometerdetects current

20
Uses of electromagnets(cont.)

• Motors
• Use electromagnets to convert electrical energy
  into mechanical energy
• An electromagnet turns inside a permanent magnet

21
Motors
22
If current moving through a wire produces a
magnetic field, I wonder
.What would happen if we move a wire through a
magnetic field
23
I bet it has never been tested. Lets try it!!!
Ill try anything once!!
24
Havent we already done that?
Joseph Henry
Michael Faraday
25
Faraday and Henry discovered that moving a wire
through a magnetic field, or moving a magnetic
field through a coil of wire induced a current
on the wire!! Electromagnetic Inductionprocess
in which moving a wire through a magnetic field
produces a current on the wire.
26
.produces a current on a wire.Did we just
create electricity

• Generatorsuse electromagnets to convert
  mechanical energy into electrical energy.

27
Generators
28
Other Uses of electromagnets
Transformers
Are you talking about me?
Not this Kind!!!!
29
Alternating vs. Direct Current

• Alternating Current

• Direct Current

• Current alternates, one direction, then the other.

• Current only goes in one direction.

Plug it in, Plug it in!!
30
Transformers

• Used to increase or decrease the voltage of
  alternating currents.

31
Transformers

• Consist of 2 coils of wire.
• Primary Coil
• Alternating current enters
• Secondary Coil
• Alternating current leaves
• Its the difference in the number of turns of
  wire on each coil that causes the voltage the
  change.

32
2 Types of Transformers

• Step-up Transformer
• Increase voltage
• Secondary more turns than primary

• Step-down Transformer
• Decrease voltage
• Primary more turns than secondary

33
Math of a Transformer
34
A step-up transformer has 400 turns on its
primary coil and 600 turns on its secondary coil.
If the primary coil is supplied with 120 V of
alternating current, what will be the secondary
(output) voltage?
ns 600 turns np 400 turns Vs
? Vp 120
35
Example 2
36
(No Transcript)
37
Example 3
38
(No Transcript)