Topic 7 - Magnetism and Electromagnetism Flashcards
What is an alternator?
A device that makes use of the generator effect to generate alternating current.
What is attraction?
Opposite poles will experience a force of attraction, meaning they will
experience a force towards each other. The force between a magnet and
magnetic material is always one of attraction.
What are current carrying wires?
When current flows through a wire, a magnetic field is
generated around it. The strength of the field is dependent on the magnitude of the current and the distance from the wire.
What is a dynamo?
A device that makes use of the generator effect to generate direct current.
What is an electric motor?
A current-carrying coil of wire in a magnetic field. The two sides of the coil that are perpendicular to the magnetic field experience
forces in opposite directions, causing rotation.
What is a electromagnet?
A solenoid with an iron core.
What is Fleming’s left hand rule?
A rule used to determine the orientation of the force (thumb), current (second finger) and magnetic field (first finger) when a
current-carrying wire is placed in a magnetic field (motor effect).
What is the generator effect?
When there is relative motion between an electrical
conductor and a magnetic field, a potential difference will be induced across
the ends of the conductor. A current will flow if this conductor is part of a
complete circuit.
What is an induced magnet?
A material that becomes a magnet when it is placed in an existing magnetic field, but loses its magnetism quickly once it is removed.
Induced magnetism always produces attractive forces.
What is a magnetic compass?
A device containing a small bar magnet that points in the direction of the Earth’s magnetic field.
What are magnetic field lines?
Lines representing the strength and direction of a magnetic field. The field line direction at any point is in the direction that a force would act on another north pole if placed at that point.
What are magnetic fields?
The region around a magnet in which another magnet or
magnetic material will experience a force.
What are magnetic materials?
Iron, steel, cobalt and nickel.
What are magnetic poles?
The regions of a magnet where the magnetic forces are at their strongest.
What is a microphone?
A device that uses the generator effect to convert the pressure variations of sound waves into variations in the electrical current of a circuit.
What is the motor effect?
When a current-carrying wire is placed in a magnetic field, a force will be experienced between the wire and the magnet responsible for the field.
What is a permanent magnet?
A magnet that produces it’s own magnetic field.
What is repulsion?
Like-poles will experience a force of repulsion, meaning they will experience forces in opposite directions.
What is a solenoid?
A wire wrapped into the shape of a coil, that has a strong and uniform magnetic field inside of it. The solenoid’s magnetic field strength can be increased
by adding an iron core.
What is a step down transformer?
A transformer that has a smaller potential difference in the secondary coil than in the primary core.
What is a step up transformer?
A transformer that has a larger potential difference in
the secondary coil than in the primary core.
What are Tesla?
The unit of magnetic flux density.
What is a transformer?
An iron core with a primary and secondary coil of wire wound around opposite ends.
What is the difference between a permanent magnet and an induced magnet?
- A permanent magnet produces it’s own magnetic field
- An induced magnet becomes magnetic when placed in a magnetic field
In what direction does a magnetic field point?
- In the direction that a north pole would experience a force if played in the field
- From the north seeking pole to the south seeking pole of a magnet
What is produced when current flows through a conducting wire?
A magnetic field is produced around the wire.
Describe the magnetic field found inside a solenoid?
Strong and Uniform.
What criteria must be met for the equation linking force, magnetic flux density, current and length to hold?
The conductor must be at right- angles to the magnetic field it is placed in
How do loudspeakers make use of the motor effect?
The motor effect is used to convert variations in the current of an electrical circuit into the pressure variations which produce audible sound.
Explain how a loudspeaker works.
- A cone with a wire wrapped around it is connected to an a.c power supply and is placed in a permanent magnetic field
- When current flows through the wire, it created a second magnetic field, which interacts with the permanent field.
- This produces a force which causes the cone to vibrate
How is the pitch of the sound from a loudspeaker changed?
- The frequency of the a.c current is altered
- This creates a different frequency of vibration in the cone
What electromagnetic effect does a microphone take advantage of and how?
- The generator effect
- It converts the pressure variations in sound waves into alternating current in a circuit.
