1. Learning Objective
To be able to:
Describe an electromagnet and how its strength can be increased
Key Words:
Field lines, wire, current, core

2. Exam question Wednesday, 22 May 2019 Electromagnets
Date and title in books. You need a pen, pencil & ruler.
Starter Activity – 5 minutes
Exam question

3. (F)
Target 1-9
Draw a diagram to show a magnetic field around an electromagnet
(F/H)
Target 4-9
Describe an electromagnet and why is it an improvement to a solenoid
(H)
Target 5-9
Explain how factors can be changed to increase the strength of an electromagnet
Extension: Application of Knowledge
Target 8/9
Discuss the uses for an electromagnet and its limitations
Learning Outcomes

4. Making an electromagnet
When electricity is passed through a coil of wire, the coil has a magnetic field around it. This is called an electromagnet.
If the coil of wire is wrapped around a piece of iron, such as an iron nail, the magnetic field gets stronger.

5. Practical Activity
Make an electromagnet, the same way we did last week.
This time, we are going to use different materials for the core of the electromagnet.
How might we find out which magnet is the strongest?
Pick up paperclips of course!

6. Planning A Write down the question you want to answer.
B We want to find out if the core changes the strength of an electromagnet. The input (independent) variable you are changing is
•the ___________ inside the wire
C The input variable your group is going to investigate is the core material used to make your electromagnet. The outcome (dependent) variable is the strength of the electromagnet you make. We will measure this by counting how many ___________ the electromagnet will pick up.

7. D We will keep these variables the same to make it a fair test (make a list):
E We will need the following equipment (make a list using the list above to help you):
F We will _______ each measurement to make sure our results are reliable.
G We predict that the core of the electromagnet will change the ____________ of the electromagnet.
H We think this because:

8. Planning
2 Think about how you will do your investigation. Draw a diagram to show how you plan to set up your equipment. 3 How many readings do you plan to take? 4 How many times will you repeat your readings? 5 What range of values will you take for your input variable?

9. Number of paper clips picked up
Recording Results
Core material
Number of paper clips picked up

10. Conclusion Complete these sentences about your practical
I found that the most paper clip were picked up by _____________
I found that the least paper clip were picked up by _____________
I think the best material for the core of an electromagnet is ____________________

11. Investigating an electromagnet
An iron core at the centre of a coil of wire, increases the strength of an electromagnet.
Two experiments can be carried out to investigate the other factors that can affect the strength of an electromagnet:
1. Investigate how the number of coils affects the number of paper clips attracted to an electromagnet – keep the current the same in this experiment.
2. Investigate how the size of the current affects the number of paper clips attracted to an electromagnet – keep the number of coils the same in this experiment.

12. The Teams
Team Turns
Team Current

13. Our investigation
One half of the class will be investigating how current affects an electromagnet.
One half of the class will be investigating how the number of turns of coil affects the class.
You have been given a sheet for your experiment!
Write your prediction for your experiment on the sheet!

14. Feeding Back
Team Turns: What did you find out about adding more turns of wire?
Can you explain why this happens?
Team Current: What did you find out about increasing the voltage?
How is current and voltage linked?
Can you explain what you found out using science?

15. Final Task Answer the following questions in your book!
What happens to the strength of an electromagnet as your add more turns of wire?
Do you think a scrap yard electromagnet has a few or lots of turns of wire? Explain your answer.
What happens as you increase the current in an electromagnet?
Explain why this happens using scientific ideas.
Why might we not want a really big current going through a wire in an electromagnet? What could we do instead to make the electromagnet stronger?