# Magnetism - PowerPoint PPT Presentation

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Magnetism. Observe:. N. S. N. S. Attract or repel?. Observe:. S. N. N. S. Attract or repel?. Observe:. N. S. S. N. Attract or repel?. Observe:. N. S. N. S. Attract or repel?. Observe:. N. S. Make a map of the magnetic field around the bar magnet. N. S.

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Magnetism

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## Magnetism

### Observe:

N

S

N

S

Attract or repel?

### Observe:

S

N

N

S

Attract or repel?

### Observe:

N

S

S

N

Attract or repel?

### Observe:

N

S

N

S

Attract or repel?

N

S

### Make a map of the magnetic field around the bar magnet

N

S

Make a map of the magnetic field around the horseshoe magnet

S

N

### Try this.

What does the current in the wire do?

B

S

N

I

B

### A current makes a magnetic field

I

I

B

B

• This is called the right hand rule

### Fields

• If you put a ______ in a __________ field, it will experience a force.

### Fields

• If you put a ______ in a __________ field, it will experience a force.

• If you put a mass in a gravitational field, it will experience a force.

### Fields

• If you put a ______ in a __________ field, it will experience a force.

• If you put a mass in a gravitational field, it will experience a force.

• If you put a charge in an electrical field, it will experience a force.

### Fields

• If you put a ______ in a __________ field, it will experience a force.

• If you put a mass in a gravitational field, it will experience a force.

• If you put a charge in an electrical field, it will experience a force.

• If you put a magnetin a magnetic field, it will experience a force.

### Oddly enough…

Electrical and magnetic fields can attract and repel.

Gravitational fields seem to only attract

### The relationship between electricity and magnetism

A moving charge affects a magnet

A moving magnet affects a charge

### The relationship between electricity and magnetism

A moving charge affects a magnet

… it makes a magnetic field

A moving magnet affects a charge

… it makes an electrical field

### The relationship between electricity and magnetism

A moving charge affects a magnet

… it makes a magnetic field

A moving magnet affects a charge

… it makes an electrical field

• There is an application of the right hand rule for each of these

### The relationship between electricity and magnetism

A stable magnetic field affects a charge…

A stable electrical field affects a magnet…

### The relationship between electricity and magnetism

A stable magnetic field affects a charge…

… only if the charge is moving

A stable electrical field affects a magnet…

…only if the magnet is moving

### The relationship between electricity and magnetism

A stable magnetic field affects a charge…

… only if the charge is moving

A stable electrical field affects a magnet…

…only if the magnet is moving

• There is an application of the right hand rule for each of these

### Electromagnets

• A coil of wire, carrying a current makes a magnetic field.

• If you put the coil around a piece of iron or steel, it becomes an electromagnet.

### Electromagnets

• A coil of wire, carrying a current makes a magnetic field.

• If you put the coil around a piece of iron or steel, it becomes an electromagnet.

• Where could you use an electromagnet?

### Solenoid

If a magnet can move into and out of the coil, it is called a solenoid.

### Solenoid

If a magnet can move into and out of the coil, it is called a solenoid.

• Where could you use a solenoid?

### Electric motors

• An electric motor converts electrical energy into work, usually rotational motion.

• Usually, a magnet makes coil of wire rotate when a current is flowing.

### Which direction is the force on the wire?

• Use the right hand rule !

• B = the magnetic field =index finger

• F = force on the wire =palm

• I = the (+) current=thumb

• F = force on the wire =palm

• I = the (+) current=thumb

• B = the magnetic field =index finger

I

B

I

B

### Mechanical Energy Electrical Energy

Motors

--Convert electrical energy into mechanical energy

--An electric current causes a coil of wire to spin in a magnetic field

--The rotational motion can do many jobs

### Mechanical Energy Electrical Energy

Generators

--Convert mechanical energy into electrical energy

--A coil of wire spinning in a magnetic field causes an electric current

--There are many ways to spin the generator

### Mechanical Energy Electrical Energy

Motors

--Convert electrical energy into mechanical energy

--An electric current causes a coil of wire to spin in a magnetic field

--The rotational motion can do many jobs

Generators

--Convert mechanical energy into electrical energy

--A coil of wire spinning in a magnetic field causes an electric current

--There are many ways to spin the generator

1

2

3

4

5

6

Mechanical Energy Electrical Energy

Generator: If you move the wire, the force is exerted on the charge

Motor: If you move the charge (a current), the force is exerted on the wire

• I

• B

• B

• EMF

• Force

• B = the magnetic field =index finger

• EMF = force on the charge

• =palm

• v = velocity of moving wire=thumb

v

B

v

B

EMF

v