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Investigate the strength of an electromagnet

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Investigate the strength of an electromagnet.


Battery : to give the electrons a push and supply the power.

Ammetre : to measure current flowing through the component (in amps)

Electromagnet : to measure its strength and see if it connects with the amount of coils wrapped around it.

Variable Resistor : to control the amount the electrical energy flowing through the circuit. It will be used as a safety device as it can make sure that the current does not exceed 3 amps. This is because the wire can get hot and this is not safe. It will also effect our results if the wire gets hot.  

Switch : Control flow of electrons. It is also a safety device to stop the current flowing unnecessarily.


  • First we will set up the circuit as shown above wrapping ten coils around the electromagnet as this is the minimum number of coils we are going to use.
  • Place 100 staples in your hand and hold it out with a distance of 3cm in between your hand and the electromagnet.
  • Switch on the voltage of the power pack to 3v.
  • Switch on the ammeter and switch.
  • Remove your hand so there are staples hanging from the electromagnet.
  • Check the ammeter and make observations before removing your hand from the switch.
  • Record results.
  • Take the staples and count them and record results.
  • Repeat this procedure ten times in exactly the same way but each time increasing the number of coils wrapped around the electromagnet by ten (e.g: 10, 20, 30, 50 ……..)


The number of coils wrapped around the electromagnet. (increase by ten)


The number of staples picked up; therefore determining the strength of electromagnet.


  • Same voltage on power pack (3volts.) This is because if the voltage is not the same the results will be affected as a higher voltage means more staples picked up as there is a larger magnetic field
  • Same size of staples; as the electromagnet may pick up many small staples and only a couple of big ones.
  • Same amount of staples held out.
  • Same electromagnet. i.e size etc. as larger electromagnet may mean stronger therefore larger magnetic field.
  • Same wire. i.e strength, thickness, and length
  • Same distance between hand with staples and electromagnet. As the further away the hand is to the electromagnet the less it will pick up making inaccurate results.


  • We will have a variable resistor in the circuit to make sure that the ammeter reading does not go over 3 amps which may cause it to heat up and this is dangerous
  • We will have a switch so that the flow of electrons is controlled and the wires do not heat up. This will also mean that the circuit will only be used when necessary.
...read more.



Number of

Number of nails picked up in the:



coils wrapped

(of two best

(in volts)

around iron

1st attempt

2nd attempt

...read more.


I believe that the scientific reasoning in my prediction matches the reasoning of the actual test as I said that more coils will mean larger magnetic field and consequently more nails are picked up. This is what happened and as more wire was wrapped around the iron core, the magnetic field became stronger and more nails were picked up.

I think that my conclusion is firm in showing a trend, so is my graph as I now know the general rule. Unfortunately, it is not very firm in showing the exact increase and decrease of strength as the number of coils increase and decrease. However, I did manage to observe that the average results were increasing by about 2-3 each time, but there is no exact constant increase.    

Finally, I can say that I am fairly happy with my results as I have successfully ‘investigated the strength of an electromagnet’ even though they are not brilliantly precise.

Physics coursework

-  -

...read more.

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