New
New
Year 11
AQA
Foundation

An electromagnet

I can describe how to test the strength of an electromagnet.

New
New
Year 11
AQA
Foundation

An electromagnet

I can describe how to test the strength of an electromagnet.

Lesson details

Key learning points

  1. When there is an electric current in a wire, there is a magnetic field around the wire.
  2. An electromagnet is a magnet that can be turned on with an electric current, and turned off.
  3. The magnetic field of an electromagnet is similar to the field around a bar magnet.
  4. A soft iron core in an electromagnet becomes magnetised and adds to the strength of field when the electromagnet is on.
  5. When there is an electric current in a coil of wire, the magnetic field around each loop adds to make a stronger field.

Common misconception

A magnetic field is the same as the electric field around a charged object.

Demonstrate that an electromagnet does not attract small pieces of tissue paper, as a balloon with a static charge can do.

Keywords

  • Coil of an electromagnet - is an insulated wire wound into the shape of a spring.

  • Turn of wire - is a single loop of wire in a coil.

  • Soft iron - is very pure iron that cannot be made into a permanent magnet.

  • Directly proportional to - describes the relationship between two variables, in which doubling the value of one variable doubles the value of the other.

  • Error bars - show the accuracy of each measurement on a graph.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Which of the following instruments can show whether you are facing north?
ruler
Correct answer: compass
protractor
pointer
trundle wheel
Q2.
Which of the following statements are correct?
All metal elements are magnetic materials.
Correct answer: Most metal elements are not magnetic materials.
All alloys (mixtures of metals) are magnetic materials.
Correct answer: Some alloys (mixtures of metals) are magnetic materials.
Some non–metal elements are magnetic materials.
Q3.
Which of the following would be attracted to the north–seeking pole of a magnet?
the north–seeking pole of another magnet
Correct answer: the south–seeking pole of another magnet
Correct answer: a piece of unmagnetised steel
a negatively charged piece of plastic
a positively charged piece of plastic
Q4.
Which of the following statements are correct?
Earth has a north–seeking pole near its geographic North Pole (in the Arctic).
Correct answer: Earth has a south–seeking pole near its geographic North Pole (in the Arctic).
Correct answer: The north–seeking pole of a magnet is attracted towards geographic north.
The south–seeking pole of a magnet is attracted towards geographic north.
Q5.
Which of the following statements about magnetic field lines are correct?
Magnetic field lines are real.
A field line of a bar magnet can have gaps in it.
Correct answer: The closer together the field lines, the stronger the field.
Correct answer: Near the S pole of a bar magnet, the field line arrows point towards the S pole.
Q6.
What do the arrows on magnetic field lines show?
The direction of force on a positive charge.
The direction of force on a negative charge.
Correct answer: The direction of force acting on the north–seeking pole of another magnet.
The direction of force acting on the south–seeking pole of another magnet.

6 Questions

Q1.
Which of the following explains why a compass is affected by a current–carrying wire made of copper?
The wire is positively charged.
The wire is negatively charged.
Magnets are attracted to copper.
Correct answer: There is a magnetic field around the wire.
Q2.
Which of the following are reasons why soft iron is used for the core of an electromagnet?
Correct answer: It is a magnetic material.
Correct answer: It loses its magnetism easily.
It is a good conductor of electricity.
It is easy to mould into the right shape.
It strengthens the field of the electromagnet.
Q3.
A pupil investigates the relationship between the current in an electromagnet’s coil and the number of pins the electromagnet can pick up. Which of the following are control variables?
Correct answer: the size of the pins
Correct answer: the material of the pins
the number of pins used
the size of the current in the coil
Correct answer: the number of turns of wire in the coil
Q4.
A pupil compares the strengths of different electromagnets by counting how many paper clips each can pick up. Which of the following explains why small paper clips are more suitable than large ones?
Larger numbers are easier to show on a graph than smaller numbers.
They are less likely to become permanently magnetised by the electromagnets.
Correct answer: Smaller differences between the strengths of the electromagnets can be measured.
Q5.
Two variables, $$p$$ and $$q$$, are related but are not directly proportional to each other. Which of the following are possible graphs of $$p$$ against $$q$$?
Correct answer: a curve that passes through (0, 0)
a straight line that passes through (0, 0)
Correct answer: a straight line that does not pass through (0, 0)
Q6.
Which of the following describes what error bars are?
markings that are made on the anomalous points on a graph
lines that show the relationship between the variables on a graph
Correct answer: lines that show the range of possible values of a point on a graph
rails put around experimental apparatus so that it does not fall off the table