T7:Magnetism and electromagnetism

1. What place on a magnet is where the magnetic forces are the strongest?

2. What happens when two magents are brought close together?

3. What happens when two like poles are brought together?

4. What happens when two unlike poles are brought together?

5. What kind of force is attraction and repulsion between two magentic poles an example of?

1. The poles.

2. They exert a force on each other.

3. They repel each other.

4. They attract each other.

5. A non-contact force.

1. What is a permanent magnet?

2. What is an induced magnet?

3. What kind of force does induced magnetism always cause?

4. What happens when an induced magnet is removed from a magentic field?

1. A permanent magnet produces its own magentic field.

2. An induced magnet is a material that becomes a magnet when it is placed in a magentic field.

3. A force of attraction.

4. It loses most/all of its magentism quickly.

1. What is a magentic field?

2. What are the 4 magnetic material?

3. What is always the force between a magnet and a magnetic material?

4. What does the strength of a magnetic field depend on?

5. Where is the magentic field the strongest at?

1. A magnetic field is the region around a magent where a force acts on another magnet or on a magnetic material.

2. Cobalt,iron,Nickel and Steel.

3. A force of attraction.

4. The distance from the magnet.

5. The poles.

1. What is the direction of a magentic field line?

2. What does a magnetic field compass contain?

3. What direction does the needle of the magnetic field compass point in?

4. What can be used to plot the magentic field patttern of a magent?

5. Draw the magentic field pattern around a bar magnet?

6. What evidence is there that the core if the earth must be magentic?

1. From N to S.

2. A small bar magnet.

3. The direction of the Earth’s magnetic field.

4. A compass.

5. To the left.

6. When not near a magnet, a compass needle always points North.

1. What is produced when a current flows through a conducting wire?

2. What 2 things does the strength of the magnetic field depend on?

3. what is the name of the shape of wire used to increase the strength of a magentic field created by a current through a wire?

4. How can we describe the magentic field inside a solenoid?

5. What is the shape of the magnetic field around a Solenoid similiar to?

1. A magnetic field.

2. The current through the wire and distance from the wire.

3. A solenoid.

4. Strong and uniform.

5. A bar magnet.

1. What can you add to increase the strength of a Solenoid?

2. What is an electromagent?

3. What can be used to demonstrate the magnetic effect of a current?

4. Draw the magentic field pattern for a solenoid

5. What are two different elctromagentic devices it can be used in?

6. What rule is used for to fidn the direction of the magentic field in a solenoid?

1. An iron core.

2. An electromagent is a Solenoid with an iron core.

3. A compass.

4. To the right.

5. A relay or a door bell.

6. The right hand rule.

1. What is the motor effect?

2. What does each finger represent in Flemming’s left hand rule?

3. What three factors affect the size of the force on the conductor?

4. What is the formula to calculate the force exerted ona conductor at right angles to a magnetic field and carryign a current?(include units)

1. When a conductor carryibng a current is placed in a megntic field, the magnet producing the field and the conductor exert a force on each other.

2. Thumb=force, First finger=field and Second finger=current.

3. Magnetic flux density, Current and length of conductor.

4. [Image]

Come back to electric motors.

1. How does a moving coil loudspeaker works?

2. What effect do louspeakers use?

• Current creates a magentic field around the coil.

• which interacts with the permanent magnetic field.

• Producing a resultatnt force casuign the coil/cone to move.

• When the direction of the current revrses, the direction of the resulatnt force reverses.

• This produces a sound wave.

• Th motor effect.

Induced potential

Uses of generator effect.

1. What do microphones use the generator efefct to do?

2. How does a microphone work?

• Microphones use the egnerator effect to convert the pressure variations in sound waves into vraiations in current in electrical circuits.

• Sound waves cause the diaphragm to vibrate

• The diaphragm causes the coil/wire to vibrate.

• The coil/wiore cuts magentic field lines.

• A potential difference is induced across the ends of the coil of thw wire.

1. What does a basic transformer conists of?

2. Why is iron used in a transformer?

3. What is the equation to calculate the number of turns on a primary or secondary coil of a transformer?

4. What would it mean fi trasnformers were 100% efficient?

1. a basic transformer consists of a primary coil and a secondary coil wound on an iron core.

2. It is easily magnetised.

3. [Image]

4. The electrical power output would equal the electrical power input.

1. How is a current induced in a transformer?

• An alternating pd is applied to the primary coil.

• The iron core magentsises and demagnetises quickly.

• This changing magentic field induces a pd n the secondary coil.

• If the secondary coil is part of a complete cirucit, a current is induced.