What factors affect the strength of an electromagnet?

Davinder Singh Poonia 10/1

Introduction

I will be testing the factors which will make an electromagnet stronger. When insulated wire is wrapped round an iron nail and the ends of the wire are connected to a battery the nail becomes capable of picking up iron filings and paper clips. This is called an electromagnet. The nail is magnetised by the current in the wire. If the battery is disconnected then the iron clips will fall off. This is because most of the magnetism has been lost. The passage of an electric current along a wire creates a magnetic field around the wire. The fields are in the shape of a series of concentric rings. The more coils used in the electromagnet, the stronger the magnet is. If there is one coil, and another is added, then the two coils have twice the strength of one. This is because the current going through the wire makes the soft-iron core is the factor that induces electromagnetism, as so when there is more current, there will be more wire or a more magnetised core. Electromagnets are magnets which are created and are easily controlled by electricity. All magnets have a region of space around them called the magnetic field which exerts a force on any magnetic material such as iron and steel or any other magnet which enters it. This force can be attractive and repulsive. If an electric current flows through a coil of wire a magnetic field is formed around the coil creating an electromagnet. This is a magnet which can be switched on and off.

Here is a diagram which shows the magnetic fields around one turn of a coil

To carry out this investigation I will follow the following steps: Insulated copper wire was coiled around a metal nail to make turns and then inserted into a power supply box. The coiled nail was put over a sheet of paper which had iron filings on, 6v was used and when the power was switched on the wire appeared to pick up the iron filings and this told us that an electromagnet was formed, because it was a short circuit the power supply switch of by itself and we had to reset it. As I stated before that the force can be attractive or repulsive in this case the force was attracted.

For our investigation we didn’t use iron filings but we used a soft iron which was the nail, and the wire was wrapped around the core of the soft iron. We used 'soft' iron because soft iron loses its magnetism very quickly when the current stops and normal iron keeps its magnetism when the current stops. The magnetic strength can be increased significantly if the wire is wrapped around the core of the soft iron which forms a coil which is called a solenoid. The magnetic field of each single coil builds up to produce a stronger field around the solenoid. The solenoid behaves as a weak magnet; one side behaves as a north pole and one as a south pole. When current flows through the coil, the iron becomes magnetised. When the current is switched off the magnetic field collapses and the iron becomes demagnetised. This is the principle of an electromagnet. Electromagnets are ‘multi – purpose’ because they are so easily controlled and they are used in places like trains and circuit breakers. The strength of an electromagnet can be varied by: changing the number of coils of wire – the more coils, the stronger the magnet. More wire in one area means that the magnetic field is reinforced by other magnetic fields. A larger magnetic field is created (assuming that the current stays the same), and also by changing the current – the larger the current, the stronger the magnet (assuming the number of coils stays the same). The wire also has to remain the same because different wires could have different resistance. Presuming that the resistance of the wire stays the same then you have to change the voltage to change the current. Current changes in direct proportion to the voltage.

Hypothesis

I hypothesise that the variables that will change the strength of the electromagnet are the number of turns in the coil of wire. I also predict that the increase of current (voltage) will make the electromagnet stronger. The points I have made in my introduction back up my predictions.

This is a preview of the whole essay

Hypothesis

To keep the wire variable the same I will use the same wire for each experiment, this keeps the resistant constant. The amount of current (voltage) will be easy to keep the same as you need a key to change the voltage in the power supply I will be using, when we need to change the voltage we will just have to call the teacher over and he will change it because there will be not enough keys to have one per group.

Plan

I am going to test how my variables will influence the strength of the electromagnet. My variables will be amount of turns on the coil and the amount of current. I will use power supply, wire, steel nail, paper with lines marked on keeping 2 mm distance apart and also we need a paper clip. This is how I will carry out my experiment:

I will get a sheet of plain A4 paper and mark on horizontal lines across the page, 2mm apart. This will act as my ruler when measuring the strength of my electromagnet.
I will plug in my power supply to the plug and check that it is on the correct voltage.
I will then coil my wire around my steel nail. Checking that I have used the appropriate amount of turns, for the experiment I will carry out.
I will connect my electromagnet to my power supply and turn it on so the electromagnet becomes magnetised.
Before I turn the electromagnet on I will put the nail on a line where it is 0mm to keep it a fair test.
I will measure how far apart the paper clip will be before being picked up.

Here is a diagram to show how my experiment will be set out

To keep this a fair test I will use the same wire as it will have the same amount of resistance. I will also use the same paperclip as other paperclips could be slightly charged. The same power supply will be used as some power supplies give out different voltage even if the difference is small.

Because my variables will be the same, I can expect my results to be of suitable accuracy. I think that these steps are reliable and anyone, anywhere, anytime can carry this experiment out following my steps and I am confident that they will get similar results but there might be a slight difference because of the equipment is different. I think that the variable which will have the biggest influence on how strong my electromagnet is will be the coils and the number of turns. I predict this because the bigger the range of the magnetic field the more distance the paperclip can be picked from.

Aim

To find out what factors affect the strength of an electro magnet.

Method

We got a power supply and connected an insulated copper wire to it. We coiled the wire around an iron nail. We coiled the wire different amounts of times and different voltages. We then got a piece of paper and we put some measurements on it which went up in 2mm, and at the point of 0 we put a line going vertical, we did this because we know where to put the nail each time so it is a fair test. Then we put the paper clip on different measurements, and put the switch on and measured where the paper clip was attracted by the magnetic pull. To keep it a fair test we kept the same power supply, the same paper clip, we kept the same iron nail, the same position of the iron nail, the same insulated copper wire, the same paper which has got the measurements. We changed the number of turns to 10, 20 and 30 and we kept the voltage the same. Then we kept the coils the same and changed the voltages. We did the experiment twice for each one, to get and accurate reading.

Results

Here are the averages for the results above

I also collected Anisha’s group’s results so I can compare if the equipment makes any difference to the strength of the electromagnet.

Analysing- conclusion

My results show that the more voltage there is the further distance the paperclip can jump from and also the more coils the more distance the paperclip can jump from.

I have drawn graphs to show my results which will make it easier to see the dissimilarity and also to compare them. Here are my graphs

With the first and second test I can see that they are nearly the same and don’t have much difference between them. This shows to me that I have carried out a fair test and also it shows me that the electromagnets strength was altered with both the coils and the voltage. With our average and Anisha’s group’s average I can clearly see that they had 1 unexpected result and also it tells me that the equipment that we use can affect the strength of an electromagnet if changed.

With the results that I have gained I can reach to a conclusion. My experiment worked and I can prove this with my results because I know that the strength can be affected if we change the number of coil turns and also the voltage. I know my experiment worked because my results clearly state that the electromagnets strength was affected by the coils and voltage. My experiment produced these results because we carried out a fair test be keeping all the equipment the same and also we had set it out right because if it was set out wrong then the results would have not proved that the strength can be affected by the no. of coils and the voltage.

On the graph which shows the averages I decided to do a line of best fit because that one joins both tests into one. We never had an unexpected result but if we did then we could have used the line of best fit to estimate where about the mistake should be if we never made a mistake.

To explain my results I will use scientific knowledge. When I was doing my experiment when I switched the power supply off the paperclip fell in a few seconds later, this was because when the current is switched of the magnetic field collapses and the iron becomes demagnetised.

My results show that if we change the no. of coils or the current its changes the strength of the electromagnet, this is because the electromagnets are versatile because they are so easily controlled.

The conclusion I have reached is that the strength of an electromagnet can be varied by changing the number of coils of wire, changing the current and changing the equipment. This is correct because on my results the higher the voltage the more distance the paperclip can jump from and also the higher the number of coils the further distance it can jump from. To prove that we can affect the strength with different equipment is the graph of Anisha’s results which clearly show the difference the equipment can make. My prediction was correct because in my prediction I predicted that that the variables that will change the strength of the electromagnet are the number of turns in the coil of wire. I also predict that the increase of current (voltage) will make the electromagnet stronger. This was my prediction and I was correct because from the graphs I came to a conclusion and the conclusion was that the no. of coil turns and the voltage will affect the strength of the electromagnet.

Evaluation:

This experiment has worked well and has produced sufficient results that produced an accurate conclusion. I did not have any unusual and anomalous results. However, the methods used were not in such way that gives the most reliable results, as, the coils were not done in exactly the same way, so the length of the coils inside the magnetic field is not precisely the same in all cases. A mechanical device could be utilized instead of doing it by hand. The results, however, are not strictly and totally accurate, as the circuit itself is not 100% efficient. The resistance inside the wires drains up some of the energy. Although I got accurate conclusion and I have backed it with scientific knowledge and I got reliable results I could have still done better. If I had to do the experiment again I would try my very best to make the coils the same and they are equally apart from another and also I would put in ammeter to get a precise reading of the current going in. This would not change my results but it will give me precise readings which will make my experiment more accurate then jus saying 2v, 6v, 12v when some of it is being decreased by resistance. I think I have carried out a fair trial.

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