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Electromagnets - What factors affect strength of an electromagnet?

Extracts from this document...


Manal Javed                                                                                                                                                                  08/11/2008                    

A magnet consisting essentially of a coil of insulated wire wrapped around a soft iron core that is magnetised only when current flows thought the wire.


What factors affect strength of an electromagnet?


To investigate the factors affecting the strength of an electromagnet. (Attraction of paperclips)


In this coursework I will be investigating the factors that affect the strength of an electromagnet.

The main factors that affect the strength of an electromagnet are:

  • Number of turns on the coil of wire around the core
  • Strength of the current applied
  • The material of the coil

In this coursework, I have chosen to investigate:

  • How will varying the number of turns on the coil affect the strength of an electromagnet?
  • How will applying different Current affect the strength of an electromagnet?

To do this affectively, I will be carrying out series of possible experiments and then by using the results making possible hypothesis, which I will investigate further, using appropriate scientific knowledge.

Background knowledge

A magnet is an object that has a magnetic field around it. It causes materials like iron, steel and nickel to attract to it.

Electrons behave like tiny magnets, because when they spin in the same direction, a magnetic field is generated. Placing a compass near a wire carrying direct current can show that a magnetic field is created; due to the electrons moving thought the wire.

A coil of wire acts like a bar magnet when an electric current flows through it, it becomes an electromagnet. All the magnetic fields we can create are the result of moving charges.  Electromagnets make fields through large currents in wires we make.  Permanent magnets produce fields through the orientation of the electron orbits and spins of the atoms in the magnet.

...read more.


Record the number of paper lips picked up. Repeat each experiment three times with the different number of turns on core each time, to get an average.

Diagram 1, showing the position of the apparatus for experiment one.


Experiment 2: How will applying different current affect the strength of an electromagnet?

Apparatus required

  • Power pack
  • Few paper clips
  • The inside of tissue role
  •  Metre of insulated wire (to wrap around)
  • Ammeter
  • Connecting wire
  • Iron bar

Procedure of the experiment

  1. Take the wire and wrap around the tissue role’s core making a coil. Making sure that the two inches of unwound wire on each end is left.
  2. Make sure that the wire is wrapped tightly and close together.
  3. Connect the power pack with two wire ends.
  4. Connect the variable resistor to the power pack.
  5. Connect the ammeter in series.
  6. Connect the electromagnet with the ammeter.
  7. Connect the electromagnet back to the power pack to complete the circuit.
  8. Used the resistor to vary the current to the desired value.
  9. Check that this value is shown on the ammeter.  
  10.  Using the core of the electromagnet, try to pick up the paperclips.
  11. Record the number of paperclips picked up
  12. Repeat each experiment three times, with different current values to get an average result.

Diagram 2, showing the position of the apparatus for experiment two


Safety measures

Safety is needed during any type of experiment carried out. Experiment I carried out, involved handling with electricity, therefore taking safety measures was an important part of experiment:

  • Make sure that there was no bare insulation or any water near any electrical appliance to prevent electrocution.
  • Make sure that too much current is not applied to the circuit, as a greater current can make the wire too hot, and cause a fire hazard.
  • Make sure there is no water around the equipment and that hand is not wet when carrying out the experiment.
  • Don’t touch the rheostat/variable resister, as it can get hot.
...read more.


If I were to change my experiment, I would try using iron fillings instead of paperclips to see whether it would give me more accurate and reliable results. Irons filling are appropriate, because they would be more accurate in weight as they are smaller. I would also use a better power pack, one which can exceed above 5 amps. This would help me obtain more results and a greater graph to see if my straight line continues on. I would also have a bigger coil, to be able to attract more paperclips, so that it would also have more turn on the coil and more paperclips attracted, which would again increase my results capability.

To increase the reliability of my results, I would use fresh paperclips after each test, because I believe that paperclips that have already been used in the experiment still carry the magnetic charge, which could distort the results.

I could carry out further work related to this investigation.  I could also investigate the material of the coil, which is another factor affecting the strength of an electromagnet. I could investigate this, by placing different materials, like iron, copper, and steel inside the core of the electromagnet, I would keep current and the number of turns constant. The strength will be tested, by the number of paperclips attracted. The evidence I should achieve is, when the current increases in a material with a less resistively, the strength of an electromagnet also increases.  

Overall I did enjoy investigating the aspects of electromagnet. I manage to prove my hypothesis, with my results, obtained during the experiment.

Physics investigation: Electromagnets

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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