Do Now (2/5/14)Do not touch the materials on your desk until instructed to do so.

1) Are all metals magnetic?

2) Can non-magnetic materials interact with magnets?

Intro to Electromagnetism

Copper Tube Demo• You will have 10 minutes to complete the Demo Activity.

• Do not drop the magnets on the floor!

• Please ignore air resistance in your answers.

Copper Tube

• What did you observe when you dropped your pencil?

• What did you observe when you dropped the magnet?

• Was the magnet attracted to the copper tube?

• What guesses did you come up with for why this occurs?

Electric Current and Magnetism

• In 1820, it was hypothesized that the electric current must produce a magnetic field around the wire.

• Michael Faraday wondered if the reverse might be true!?!

Energy Transfer

What type of energy transfer is this?

Kinetic Energy to Electrical Energy

He discovered that he could induce current by moving a wire through a magnetic field

Inducing a Current

• It is the relative motion between the wire and the magnetic field that produces a current.

What if the wire moved parallel to the Magnetic Field?Would current be produced?

NO CURRENT IS PRODUCED IF THE WIRE MOVES PARALLEL TO THE MAGNETIC FIELD

Current

• What sort of shape do magnetic field lines form around a current carrying

wire?

Exit Question:A wire of length 10 cm moves parallel along a magnetic

field of strength 8T such that none of the field intersects the wire. If the wire is moving 500 m/min what is the resulting current through the wire?

Do Now (2/6/14)1. What must be true for a current to be induced in a wire as the wire

moves through a magnetic field?

2. A uniform magnetic field B, with magnitude B = 1.2 x 10-3 T, points vertically upward throughout an enclosed space. A proton with a velocity v = 3.2 x 107 m/s enters the space moving horizontally from south to north.

• Find (a) the magnitude and (b) the direction of magnetic field.

Lets Change Gears

What is the direction of centripetal force?

Towards the center of the circle

What is the name of a force acting on an object that moves in a circular path?

Mass Spectrometer• Mass Spectrometer

o Measures the mass of an unknown atoms or molecules

RHR• Why does the particle curve downwards?

Radius of the CircleName the two forces in the diagram

Magnetic force == centripetal force

Lets solve for the radius of the circle:

r

mvqB

qB

mvr

Identify our Variables

• m = Mass

• v = Velocity

• q = Charge• B = Magnetic Field Strength

• r = Radius

Apply RHR

Is this particle an electron or proton?

Proton

RHR

How do we know if this particle is an electron or proton?

Moving through a Voltage

• V = voltage• v = velocity• Q = Charge• M = Mass m

qVv

2

Classwork

Use the rest of class time to work on your homework.

‘Interaction between E and B and matter’

Do Now (2/7/14)

• An electron moves at 4.2 x 105 m/s as it passes through a magnetic field. What is the radius of it’s circular path?

Electricity• What are different ways we generate electricity?

• Hydro-electric Dams• Wind Power• Generators• Solar Power• Fossil Fuels

What type of energy transfer is this?

Kinetic Energy to Electrical Energy

EMF

A current is induced

• A force is exerted on the charges in the wire.

• This increases the electric potential energy on the charges.

What occurs if a wire moves through a magnetic field?

EMF

• What have we learned before that uses the word ‘potential’?

Potential Difference! (ΔV)

This change in potential, or potential difference is called the induced electromotive force, or EMF.

• Electromotive Force (emf) - IS NOT A FORCEo It was defined before we fully understood electricity.o Think of it as a voltage.

• The EMF (ε) is measured in volts and depends on:

ε = B l vWhere l is the length of the wire.

EMF

Classwork

Use the rest of class time to work on your homework. Either:

‘Interaction between E and B and matter’Or

‘Electromagnetic Induction’

Cool videosFeel free to watch these on your own time

http://www.youtube.com/watch?v=txmKr69jGBk

magnet:http://www.youtube.com/watch?v=FM3LVrKXFcA