An investigation into how the strength of an electromagnet is affected by varying the current

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An investigation into how the strength of an electromagnet is affected by varying the current


I am investigating whether, and if so, how an electromagnet is affected by varying the current. An electromagnet is a magnet created by winding a wire around a soft iron c-core and running a current through the wire. Current is measured in Amperes (A).

Variables available



·N0 of coils around the c-core

Size of the c-cores (thickness/length)

Type/size of the wire coiled around the c-core

I chose to use current as my variable. I decided this because I have access to accurate equipment to measure the current, when I change it. The other available variables will be kept constant throughout the experiments.


I aim to find how varying the current in an electrical circuit affects the strength of an electromagnet.

Background Scientific Knowledge

My c-cores that I will be using will be ferromagnetic, meaning that it quickly becomes demagnetised when the current is switched off and that it is very good at increasing the strength of the magnetic field produced by the current in the wire. To become magnetic in the first place, the electrons in the c-core (the one with the wires around) will have to align themselves. This happens when they group together in domains. The majority of these domains are usually only partly aligned. When every electron in every domain is aligned, then the magnet has reached its potential and is described as "saturated." I also know that if there are more coils around the core, the electromagnet is stronger. Also the type of wire

Will affect the electromagnet's strength. I will use the Internet or an encyclopaedia to help me. I also know that Hans Christian Oersted (Ä) and Michael Faraday (Å) both found that magnetic fields and an electrical current were directly related to each other (a current can create a magnetic field).


I predict that as the current increases, the strength of the electromagnet will also increase. Furthermore, I predict that when current doubles, the strength of the electromagnet will also double.

I can see that if there is more current running through the coils:

Power = Voltage * Current (P=VI) (* means times)

This shows that if the current increases, so does the power, thus increasing the strength of the electromagnetic field. This means that as the electromagnetic field is stronger, a larger force is required to pull the metal from the electromagnet. Using my background knowledge, I know that magnetic effects are produced by a moving electrical charge (current). This tells me that the current will cause the c-core to have a magnetic field.

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I will need to use goggles in my experiment, because I will be pulling c-cores apart, and when they come apart, there will be a danger of one hitting me in the face. Common sense dictates that the variable resistor could become hot, so it will not be touched, apart from when the resistance is required to change.

Preliminary experiments

I tested my plan by doing a preliminary experiment. I checked whether I had too many coils and how easy it was to keep the voltage constant. I found that the electromagnet was too strong (I ...

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