Chapter 7 Magnetism - 7.3 Onwards

Chapter 7 Magnetism

by Ren Ghee Lee

Video Time​​

There is a (very easy) question after this to ask on your thoughts​

​

​https://youtu.be/6yhNOXQkMpY​

Open Ended

How do you think the crane can move the pieces of junk metal?

​Look at the simulation​

I will change the direction of the current. Notice what happens to the direction of the magnetic field lines?​​

Open Ended

What happens to the direction of the magnetic field lines when I switch the direction of the electrical current?

Open Ended

The core is usually made of iron, why do you think that is the case?

Question Time​

​Get ready

Open Ended

Describe how you could use an electromagnet to sort a mixture of iron and copper pieces into two separate piles of iron and copper.

Answer​

Switch on the electromagnet to attract the iron pieces. Move the magnet away and switch it off. The iron pieces then are dropped and separated from the copper​

Open Ended

What do you think would happen to the magnetic field around the single piece of wire if the direction of the current was reversed?

Answer​

It will reverse​

Open Ended

Why is iron usually used as the core for electromagnets?

Answer​

Iron is easily magnetised, but it doesn't stay magnetised when the electrical current is switched off.​

Open Ended

What would happen if you used steel as the core?

Answer​

The steel core will stay magnetised even if the electrical current is switched off​

Open Ended

A student says that an electromagnet is stronger when it has an iron core because the electric current flows through the iron as well as the wire. 

Is this correct? What would you say?

Answer​

The wire wrapped around the core is insulated. Electricity doesn't flow through the core.

​

​An electromagnet with an iron core is stronger because iron is easily magnetised.

Multiple Select

Which of the following statements is/are correct?

• You can switch off a permanent magnet

• Cranes in scrapyard use electromagnets to move iron and steel pieces

• Electromagnets can be made stronger by coiling more turns of wire around the core

• When the electrical current flowing through the solenoid is higher, the magnetic field generated is stronger

• Using a copper core in an electromagnet makes it stronger

Question Time​

Get ready​

Open Ended

What shape is the magnetic field of a wire?

Multiple Choice

What can you do to make an electromagnet stronger?

• Increase the number turns of the coil 

• Increase the current in the wire

• Use a magnetic material as the core of the electromagnet

• All of the above

Multiple Choice

When you reverse the direction of the electrical current around an electromagnet, what happens to the direction of the magnetic field?

• It stays the same

• It reverses

Experiment Time​

Let’s say we want to test how different factors affect how strong is an electromagnet.​

Open Ended

How do you think we can measure how strong is an electromagnet in a simple way?

Poll

We will be doing a simulation.

Which one of these two factors do you want to set as the independent variable?

• Number of turns of the coil

• Voltage / Number of batteries

Poll

When we are testing how the number of coils/number of batteries affects the strength of the electromagnet, can we change the other variables in the experiment?

• Yes

• No

Question Time​

Get ready​

Open Ended

Explain in your own words, what is the dependent variable of an experiment?

Fill in the Blanks

Fill in the Blanks

Fill in the Blanks

Open Ended

A group of students plan to investigate how high a ball bounces on different surfaces. The image on the left shows part of their plan.

Suggest a way to improve the accuracy of their results?

Multiple Choice

A group of students plan to investigate how high a ball bounces on different surfaces. The image on the left shows part of their plan.

A table with two columns is used to tabulate the results for the experiment.

The header for the left column is _____________, and the header for the right column is _______________.

• the type of surface, the height of the bounce

• the height of the bounce, the type of surface

Open Ended

What was one use of an electromagnet we have learnt?

Multiple Choice

Which circuit do we control with a switch?

• Low-current circuit

• High-current circuit

Multiple Choice

Which part of the circuit contains an electromagnet?

• Low-current circuit

• High-current circuit

Open Ended

What if we used permanent magnets in these machines? What would happen?

Recap Time​

Get ready​

Open Ended

Name 3 things that uses electromagnets in our everyday lives.