ACDC Transformers Electromagnets.

Magnetism, Generators, Types of current, and Transformers.

​Magnetism & Electricity

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Options (9)

Aluminum

paperclip

scissors

sewing needle

nuts & bolts

button

penny

marble

pencil lead

Classify the following materials as either magnetic, non magnetic, or both.

Magnetic

Non-magnetic

What is Magnetism?

Magnetism is a force (like gravity) and a form of energy. It is a FORCE of attraction or repulson of a magnetic material. It is due to the arrangement of the electrons in the material.

Magnetism was discovered by the Greeks. They discovered a mineral called magnetite that attracted some metals to it. It can SHOW magnetism.

The ends of a magnet are where the

magnetic effect is the

strongest.

These are called “poles.”

Each magnet has

2 poles – 1 north, 1 south.

Like poles
repel …

Opposite poles
attract !

The Law of Attraction

N S N S

If you cut a magnet in half,

you get 2 magnets!

Magnetic Fields

The region where the magnetic forces

act is called the “magnetic field”

Poles of a magnet

always

come in pairs!

The Earth is a magnet:

Earth’s magnetic

field is mostly

caused by electric

currents in

the liquid outer

core which is
composed of

conductive, molten

iron.

Food for Thought:
the north end of a compass magnet
is drawn to align with the Earth's
magnetic field. Because the Earth's
magnetic North Pole attracts the
"north" ends of other magnets, it is
technically the "South Pole" of our
planet's magnetic field.

Multiple Choice

What do the lines around this magnet represent?

• North Pole
• South Pole
• Magnetic Declination
• Magnetic Field

Multiple Choice

The strongest part of a magnet is...

• the bars.
• the force field.
• the poles. 
• the middle.

Multiple Choice

Which one represents the magnetic field lines of magnets repelling?

• A

• B

There are 2 types of magnets:

• Permanent magnets

– permanent
– Keep their magnetism all of the time
– Ex. Refrigerator magnet

• Electromagnets

– Temporary
– Can be magnetized by running electricity through it.
Ex: Car Alternator

Electromagnets

• By running electric current through a wire, you can

create a magnetic field.

• By using this simple principle, you can create all sorts

of things, including motors, speakers, disk drives and
so on.

Electromagnets

Electromagnets can be made stronger in the following ways:

1. Increase the strength of the battery.
2. Increase the number of coils around the iron.
3. Change the size of the copper wire.
4. Change the size of the iron core.

Multiple Choice

If you wrap more coils around an electromagnet, it will become 

• brighter
• stronger
• weaker
• invisible

DC = Direct Current

​Energy flows in ONE direction.

Batteries have energy that flows in from positive to negative in ONE direction.

A.C. stands for…

Alternating Current.

​Appliances run on alternating current.

AC = Alternating Current

​Created by generators, a large magnet which rotates around coils. As the rotation occurs, the direction of the positive and negative are constantly changing--the alternating of the current.

What is a transformer?

A transformer is a machine

which can transform one
voltage into a higher or
lower voltage.

e.g. 2 V can be transformed into 10 V
Or 230 V can be transformed into 6 V

How do you build a transformer?

Simple! You start with an iron core…

■ You wrap a coil of wire around one side…

How do you build a transformer?

This is going to be the primary coil.

■ You wrap a coil of wire the other side…

How do you build a transformer?

This is going to be the secondary coil.

A step up transformer

A step up transformer…

Has fewer turns on the primary than the secondary.

This means it STEPS UP the voltage. It STEPS DOWN the current.

10 V in

20 V out

A step down transformer

A step down transformer…

Has fewer turns on the secondary than the primary.

This meansit STEPS DOWN the voltage. It STEPS UP the current.

10 V in

5 V out

Transformers are an important part of the grid, because they reduce energy losses.

A step up transformer steps up the voltage, but steps down the current.

The energy is carried as a high voltage rather than as a high current.

The result of the lower current is that less energy is lost as heat.

This means energy can be carried long distances before entering a home. In order to enter a home, the energy has to step down to reduce the voltage

Multiple Choice

You're an electrician and you want to connect a house to the electric grid but you know the current is too high in the power line. What could you do within the transformer to safely step down the current to the home?

• Use a transformer with a higher number of turns in the secondary coil compared to the primary coil.
• Use a transformer with a lower number of turns in the secondary coil compared to the primary coil.
• Use a transformer with a larger core size to increase the current.
• Use a transformer with the same number of turns in the secondary coil compared to the primary coil.