[P7] Magnetism and electromagnetism

How will like poles (north & north or south & south) behave when they interact?

They will repel and push away from each other

How will opposite poles (north & south or south & north) behave when they interact?

They will attract and pull towards each other

On a magnet, where is the magnetic field strongest?

The magnetic field is strongest at the poles of a magnetic

Is the magnetic force a contact or a non-contact force?

Non-contact

What is a permanent magnet?

A magnet that produces its own magnetic field

What is an induced magnet?

A material that becomes magnetic when it is placed in a magnetic field

What is the difference between a permanent and an induced magnet?

A permanent magnet always has a magnetic field, but an induced magnet only becomes magnetic when it is placed into a magnetic field

What is a magnetic field?

The region of space where a magnetic force will act on a magnet or a magnetic material

What are the four types of magnetic material?

Iron, nickel, cobalt and steel

Is the force between a magnet and a magnetic material attractive or repulsive?

Attractive

What shape is the magnetic field around a bar magnet?

Many loops going from the North pole to the South pole

In which direction should magnetic field lines point?

Magnetic field lines point towards the south pole of the magnet

What is a magnetic compass?

A small bar magnet mounted on a pin so that it can spin around. It will point in the direction of a nearby magnetic field

Is the magnetic field around the Earth permanent or induced?

Permanent

What does the strength of a magnetic field depend on?

The strength of the magnet AND the distance from the magnet

What is a solenoid?

A coil of current-carrying wire

What is an electromagnet?

A solenoid (coil of current-carrying wire) with an iron core

What is the shape of the magnetic field around a wire?

Circular field lines around the wire

What is the shape of the magnetic field around an electromagnet?

Similar shape to the field around a bar magnet: many loops going from one end to the other end

How can a magnetic field be produced around a metal wire?

When current flows through the wire

What does the strength of a magnetic field around a wire depend on?

The size of the current in the wire AND the distance from the magnet

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What is the motor effect?

When a conductor carrying a current is placed in a magnetic field the magnet producing the field and the conductor exert a force on each other

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] In Fleming's left hand rule, state what the thumb represents

Force, F (measured in Newtons, N)

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] In Fleming's left hand rule, state what the first finger represents

Magnetic flux density, B (measured in Tesla, T)

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] In Fleming's left hand rule, state what the middle finger represents

Current, I (measured in Amps, A)

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] What affects the size of the force on the wire in the motor effect?

The size of the magnetic field, the size of the current in the conductor, the length of the conductor that is in the magnetic field

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] Describe how an electric motor works

A coil of wire carrying a current in a magnetic field will experience a force on opposite sides of the wire - this is because the direction of the force depends on the direction of the current. These opposite forces cause the wire to rotate

What effect is used inside headphones and loudspeakers?

The motor effect

What do headphones and loudspeakers convert current variations into?

Pressure variations in sound waves

What is the generator effect?

When motion between a conductor and a magnetic field induces a potentital difference, and then induces a current when connected to a complete circuit

How can induced potential difference or induced current be increased?

the speed of movement is increased OR the magnetic field strength is increased OR the number of turns on the coil is increased

What effect is used in microphones?

Generator effect

How can the direction of induced current or induced potential difference be changed?

the magnet is moved out of the coil OR the other pole of the magnet is moved into the coil

What is the basic structure of a transformer?

A primary coil and a secondary coil wound on an iron core

Why are iron cores used in transformers?

They are easily magnetised

In a step-up transformer, what is the relationship between the secondary coil potential difference and the primary coil potential difference?

The potential difference across the secondary coil is greater than that of the primary coil

In a step-down transformer, what is the relationship between the secondary coil potential difference and the primary coil potential difference?

The potential difference across the secondary coil is smaller than that of the primary coil

What type of input current is used in transformers?

Alternating current

What is the output potential difference of a step down transformers to homes and schools?

230 V