Cycle 3 test magnets and electromagnets

What is an electromagnet?

A coil of wire with a current that creates a magnetic field similar to a bar magnet.

What makes a magnetic field stronger in a wire?

Coiling it around a soft iron core.

What is a solenoid?

A coil of wire that acts like a bar magnet when current flows through it.

Why is soft iron used inside electromagnets?

It becomes magnetic when current flows

Why isn't steel used in electromagnets?

Steel stays magnetised after the current stops - not helpful if you want it switchable.

How can you increase the strength of an electromagnet?

1. Use a soft iron core 2. More turns of wire 3. Bigger current.

What happens if you reverse the current in an electromagnet?

The direction of the magnetic field also reverses.

Name 3 devices that use electromagnets.

Electric bell

Why is the North Pole actually a magnetic south pole?

Because magnetic north poles are attracted to it - and opposites attract!

What's the formula for speed?

Speed = Distance ÷ Time

What's the unit for speed?

m/s (meters per second)

What's the formula for pressure?

Pressure = Force ÷ Area

What's the unit for pressure?

N/m² (Newtons per square metre)

What's the formula for moment?

Moment = Force × Distance from pivot

What's the unit for moment?

Nm (Newton metres)

What is the normal contact force?

The upward force a surface (like a chair) exerts to balance weight.

Why is Chloe wrong to say there's no force when sitting still?

Because the forces are balanced

What is a magnetic field?

a region around the magnet where magnetic materials experience a force

what are the only magnetic materials

Iron

Fridge in red light

It looks red because it reflects the red light into our eyes—red light contains only red.

Kyle's mistake

He says the fridge always looks white

Isaac's mistake

He says red and white mix

Jasmine's mistake

She says white doesn't reflect any colours

Georgia's answer

Correct—white reflects red in red light

Harvey's answer

Correct—the fridge looks red in red light as it reflects only red.

Energy transfer (Hitting a ball)

Chemical store of arm → kinetic store of racquet

Energy transfer (Boiling water)

Chemical store → kinetic + internal thermal store.

Energy transfer (Lighting bulb)

Chemical store of battery → internal thermal store of bulb and room.

Energy (Holding a book)

Incorrect: The book has energy in a gravitational store

Energy (Lifting object with see-saw)

Incorrect: Energy isn't changed into a new type—it's transferred to a gravitational store.

Electric bell loop

Cycle continues rapidly causing repeated ringing sounds.

The Electric Bell steps

1 The switch is closed
2 current flows through the coil
3 the electromagnet is now on
4 the electromagnet attracts the soft iron bar and the striker hits the bell
5 this movement breaks the circuit at the contact
6 current stops flowing
7 the electromagnet goes off
8 the springy soft bar springs back and remakes contact
9 current flows again and the whole process repeats itself

Analysing data

when writing a conclusion say what happens to one variable as the other one increases or decreases. For example

Analysing trends in graphs

The yellow line is straight because each increase in A gives the same increase in B. This is also true in the straight parts of blue and red lines. When the blue line curves horizontally