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How does the number of coils on an electromagnet affect its strength?

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How Does The Number of Coils On An

Electromagnet Affect Its Strength?

Aim: To find out how the number of coils on an electromagnet affects its strength.

Scientific Knowledge:

An electromagnet is a temporary magnet; the magnetic field only exists when an electric current is flowing. Any electric current produces a magnetic field, but the field near an ordinary straight conductor is rarely strong enough to be of practical use. A strong field can be produced if a wire is wrapped around a soft iron core and a current is passed through the wire. The strength of the electromagnet depends on how many coils you wrap round and how high the voltage is.

The area of force (magnetic field) surrounding a bar magnet can be shown by the lines of force as shown below, although these lines are no more real than the lines of latitude and longitude on a map or globe.


When opposite poles of a magnet are brought together, the lines of force join up and the magnets pull together.


When like poles of a magnet are brought together, the lines of force push away from each other and the magnets repel each other.

Electromagnets are used to lift large masses of magnetic material such as scrap iron.  Electromagnets are also found in electrical generators, electric motors, doorbells, circuit breakers, television receivers, loudspeakers, etc.

The factors that increase the strength of an electromagnet are;

  • Increasing the number of coils, which adds more field lines and makes the electromagnet stronger.


...read more.



I predict that as the number of coils are increased the magnetic field will become stronger, because each coil has its own magnetic field, so the more coils there are the more field lines there are which means it would be a stronger electromagnet. The electromagnet will become stronger if we add more coils because there are more field lines in a loop then there is in a straight piece of wire. In a solenoid there are a lot of loops and they are concentrated in the middle, as more loops are added the field lines get larger, therefore making the electromagnet stronger. The magnetic field becomes stronger because the magnetic field around a wire is circular and vertical to the wire, but the magnet fields from each of the turns in the coil add together, so the total magnetic field is much stronger. The magnetic field around a solenoid is much stronger than a bar magnets because each coil acts like a magnet when a current is passed through it, when the coils are repeated several times it is like having several mini magnets in a row, making it more stronger than bar magnet.


Iron Nail

Power pack

Paper clips

Coil wire


Crocodile clips


  1. Collect all the equipment and paper clips, demagnetise the nail by hitting it with a hammer
  2. Connect everything together and put the voltage on the power pack to 4V
  3. Wrap the coil around the iron nail 5 times and turn the power supply on
  4. See how many paper clips it picks up then turn the power pack off  
...read more.


By looking at the graphs and lines of best fit, a few anomalous results. The first time we done the experiment we got one anomalous result, the rest of the results were quite near the line, I think this is because some of the paperclips got tangled together. In the second experiment there was only one anomalous result. I think this is because the metal was already magnetised before from the first experiment. On the third experiment there were two anomalous results, this is because the magnetism had built up from the two previous results making the third the most inaccurate result. This is mainly due to the fact that the electromagnets had not been demagnetised before each of the experiments.

If I could repeat this experiment I would demagnetise the magnet after each time I repeated the experiment, this would give a more accurate result, because I didn’t demagnetise the magnet the electromagnet kept increasing its magnetism each time. Also if I could do the experiment again I would do it much more quickly because as the metal heats up it slowly demagnetises the magnet. Another thing that I would change, is that I would change the voltage on the power pack instead of the coils, I would have done this at 1V, 2V and 3V because it would be another way of testing to see if my theory was right, by changing the continuous result. I would also change the way I conducted the experiment, instead of just dipping the paperclips into the pot, I would dangle them off each other. This would give me an accurate reading of how strong the electromagnets field is.

...read more.

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