Compacted magnetism and electromagnetism full set

What is a magnetic field?

A region where magnetic materials experience a force.

What are the magnetic materials?

Iron, steel, cobalt, nickel.

What do magnetic field lines show?

The direction and strength of a magnetic field.

Where is the magnetic field strongest?

At the poles of the magnet.

What is an induced magnet?

A material that becomes magnetic when placed in a magnetic field.

What happens when you remove an induced magnet from a magnetic field?

It loses its magnetism.

What happens when two like poles are brought together?

They repel each other.

What happens when two unlike poles are brought together?

They attract each other.

What is a permanent magnet?

A magnet that produces its own magnetic field all the time.

What does a compass contain?

A small bar magnet that aligns with Earth's magnetic field.

What does a compass show?

The direction of the magnetic field.

What is the Earth's magnetic field caused by?

Movements in the molten outer core of the Earth.

What is the shape of the magnetic field around a bar magnet?

Field lines go from north to south, forming loops.

What is the magnetic field like around a straight wire?

Concentric circles around the wire.

How do you increase the strength of the magnetic field around a wire?

Increase the current or wrap the wire into a coil.

What is a solenoid?

A coil of wire that creates a strong magnetic field when current flows.

How can you increase the strength of a solenoid’s field?

Add more turns, increase current, or use an iron core.

What is an electromagnet?

A solenoid with an iron core that can be turned on and off.

What are electromagnets used for?

Relays, cranes, circuit breakers, and MRI machines.

What is the motor effect?

A force on a current-carrying wire in a magnetic field.

What rule is used to find the direction of the force in the motor effect?

Fleming’s Left Hand Rule.

What are the directions in Fleming’s Left Hand Rule?

Thumb = Force, First finger = Field, Second finger = Current.

When does the motor effect happen?

When the wire is at right angles to the magnetic field.

What equation links force, magnetic field, current, and length?

Force = magnetic flux density × current × length (F = BIL).

What is the unit of magnetic flux density?

Tesla (T).

What is a simple electric motor?

A coil of wire in a magnetic field that spins when current flows.

What keeps the motor spinning in one direction?

A split-ring commutator.

What happens if the current or magnetic field direction is reversed in a motor?

The motor spins in the opposite direction.

What is electromagnetic induction?

The generation of a potential difference when a conductor moves through a magnetic field.

What causes a bigger induced potential difference?

Faster motion, stronger magnetic field, or more turns in the coil.

What is the generator effect?

Using electromagnetic induction to generate electricity.

What happens if the wire is part of a complete circuit during induction?

A current flows (not just potential difference).

What is an alternator?

A device that generates alternating current using slip rings.

What is a dynamo?

A device that generates direct current using a split-ring commutator.

What is the difference between AC and DC?

AC changes direction, DC flows in one direction only.

What is a transformer?

A device that changes the potential difference of an alternating current.

How does a transformer work?

It uses electromagnetic induction between two coils of wire.

What are the parts of a transformer?

A primary coil, secondary coil, and iron core.

What is a step-up transformer?

It increases the potential difference.

What is a step-down transformer?

It decreases the potential difference.

What equation links voltage and number of turns?

Vp / Vs = Np / Ns.

What is the transformer equation including current?

Vp × Ip = Vs × Is (for 100% efficiency).

Why is electricity transmitted at high voltage?

To reduce current and minimise energy loss as heat.

What is the National Grid?

A network of cables and transformers that distribute electricity.

Why is the iron core used in transformers?

It improves magnetic induction by being easily magnetised.

What type of current do transformers work with?

Alternating current (AC).

Why doesn’t the generator effect work with direct current (DC)?

Because the magnetic field must be changing.

How is energy lost in the National Grid?

As heat due to resistance in transmission wires.

How can energy loss in transmission be reduced?

Use thicker cables or higher voltage.

What does a relay do?

Uses a small current to control a larger current using an electromagnet.

Why are electromagnets used in scrap yards?

They can be switched on and off to pick up or drop metal.

How is a loudspeaker related to electromagnetism?

It uses a coil in a magnetic field to convert electrical signals into sound.

How does a microphone use electromagnetism?

Sound waves move a coil in a magnetic field to generate a current.

What affects the pitch of the sound in a loudspeaker?

The frequency of the current.

What affects the volume of the sound in a loudspeaker?

The size of the current.

How is magnetic field strength shown in diagrams?

By the closeness of the field lines – closer = stronger.

What happens if a magnet is cut in half?

Each piece becomes a smaller magnet with a north and south pole.

What is a magnetic domain?

A region within a material where magnetic fields of atoms are aligned.

Why do soft iron cores improve electromagnets?

They are easily magnetised and demagnetised.