MIMTY 3/2/11 or 3/3/11 What would you do if you had a super-powerful magnet? MIMTY.

MIMTY 3/2/11 or 3/3/11

What would you do if you had a super-powerful magnet?

MIMTY

Notes on Magnetism from CurrentMagnetic Fields

We’ve seen that electric charge creates electric fields. Magnets similarly create magnetic fields.

notes


We’ve seen that electric charge creates electric fields. Magnets similarly create magnetic fields.

Field lines travel from North to South in the most efficient path possible.


We can draw up, down, left, or right fields. But what about towards or away? We draw it like this:

•

Towards or Away or

out of the page into the page

X


We can draw up, down, left, or right fields. But what about towards or away? We draw it like this:

•

Towards or Away or

out of the page into the page

These symbols come from arrows. Toward is like the tip coming toward you. Away is like the feathers in the back.

X


The unit for measuring the strength of a magnetic field is the Tesla

How strong is this?


The unit for measuring the strength of a magnetic field is the T

How strong is this?

Small bar magnet – 0.01 T

Neodymium magnet – 0.2 T

Speaker electromagnet – 1 T

Strong lab magnet – 10 T

Notes on Magnetism from CurrentEarth’s Magnetic Fields

Earth itself has a magnetic field.

Notes on Magnetism from CurrentEarth’s Magnetic Fields

Earth itself has a magnetic field.

This field is weak, measuring only 0.00005 T. However, this is strong enough for things like compasses to work and protects us from particles streaming out from the sun.

Notes on Magnetism from CurrentInduced Magnetism

How are magnetism and electricity related? L ‘Oersted found that if he brought an electric wire near a magnet (compass), the magnet would deflect.

Notes on Magnetism from CurrentInduced Magnetism

How are magnetism and electricity related? L ‘Oersted found that if he brought an electric wire near a magnet (compass), the magnet would deflect.

It seems that moving electricity – or electric current – induces a magnetic field!

Notes on Magnetism from CurrentField around a straight wire

A straight wire is the simplest setup we can create.

The magnetic field goes

around the wire

perpendicular to it.


A straight wire is the simplest setup we can create.

The magnetic field goes

around the wire

perpendicular to it.

The farther we get from

the wire, the weaker the field gets.

There’s a trick to remembering which way the field goes.


This is called the right hand rule.

If you point your thumb along the wire, your fingers will curl in the direction of the magnetic field.

Notes on Magnetism from CurrentElectromagnets If electricity can create magnetic field

lines, it can turn ferromagnets into magnets as long as a current is running through it.

Notes on Magnetism from CurrentElectromagnets If electricity can create magnetic field

lines, it can turn ferromagnets into magnets as long as a current is running through it.

We’ll go into more depth on this later!

Notes on Magnetism from CurrentMagnetism on moving charged particles

If we shoot a charged particle into a magnetic field it will be deflected. For an electron, we can use the relationship shown here:



“Current” is the

direction the electron

is moving.

“Force” is the direction the electron will be bent.



“Current” is the

direction the electron

is moving.

“Force” is the direction the electron will be bent.

This is usually called the “FBI” rule.


For positively charged particles, just use your left hand instead of your right.

Notes on Magnetism from CurrentMagnetism on current carrying wires

Imagine we place a wire in a magnetic field. This has a whole stream of charged particles and will be bent as well.

Notes on Magnetism from CurrentMagnetism on current carrying wires

Imagine we place a wire in a magnetic field. This has a whole stream of charged particles and will be bent as well.

Our FBI rule works to predict this as well.

Vocabulary Magnetic Field

Tesla

Induction

Electromagnet

Deflection

Force field generated by a magnet.

Unit of magnetic field strength.

When one type of field is created by another type of field.

A magnet formed by the induced field of moving electric charge.

The bending of a charged particle by a magnetic field.

vocab

Summarizing Notesnotes

Take the next 5 minutes and do the following:

1) Summarize your notes in a paragraph.

2) Create 3 questions you could ask about these notes. Your questions should use verbs from the following parts of your verb sheet:

- 1 question using “knowledge” or “comprehension”

- 1 question using “application” or “analysis”

- 1 question using “evaluation” or “synthesis”

1 more question using “synthesis”

Magnetism from Current ReviewTwo magnets are shown below. Which situation best shows how the magnetic field lines will look?

SETUP A B

C D E

Magnetism from Current ReviewThe core of the Earth acts like one giant magnet. So why does a common refrigerator magnet measure a much higher strength of magnetic field in Teslas?

<

A) Because you’re farther from Earth’s core than a common magnet.B) Because the Earth’s magnetic field is spread over a whole planet.C) The materials in a refrigerator magnet can generate magnetism more efficiently than those in the center of the Earth.D) All of the aboveE) None of the above

Magnetism from Current ReviewA “dip needle” is like a compass, but moves up and down instead of side to side. At what location would you need to stand on the Earth to get the dip needle pointing straight down?

A

B

C

D

E

Magnetism from Current ReviewWe have a particle in a magnetic field as shown, moving down. Which diagram best shows which way the electron will move next?

B

SETUP A B

it won’t move

C D E

e

x x x x x

x x x x x

x x x x x

x x x x x

e e

e ee

Magnetism from Current ReviewWhich of the following would make the best material for an electromagnet?

A) wood B) pencil lead

C) skin D) iron

E) water

Magnetism from Current Practice Problems1) What would have happened in Oersted’s experiment if he had

begun rotating the wire held over the compass?2) Why does the right hand rule only work for the right hand and not

for the left? What situations might it work for the left hand?3) Explain how you would be able to determine which end of the

Earth’s magnetic field was north and which was south.4) If wires make magnetic fields, why will a magnet not stick to an

electrical wire after it’s plugged in? What does this say about the strength and direction of the induced field?

5) Older TVs work by bending charged particles with a magnetic field to hit the screen at the right spot. What would happen to the image if the strength of that field were increased? If it were decreased?

Two parallel wires are shown at right. Explain the direction each wire will bend from magnetic

fields if both have equal current flowing through them Imagine that instead of a charged wire, we had a huge, flat charged

sheet of metal with all the electrons flowing in one direction. Explain the shape of the magnetic field made by this sheet.

classwork

Exit Question #21

Why does electricity moving through a wire make magnetism?

A) All magnetic fields create electric charge

B) All electric fields create magnetism

C) Moving magnetism creates electric charge

D) Moving electric charge creates magnetism

E) Electric fields create moving magnetism

F) They aren’t related at all

MIMTY 3/2/11 or 3/3/11 What would you do if you had a super-powerful magnet? MIMTY.

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