Investigating the factors that affect the strength of an electromagnet.

What I am going to do?

Equipment list

• Power pack
• (Soft) Iron core
• Wire
• Paper clips

Method

In my investigation I am going to see how many paper clips an electromagnet can pick up, varying how many times a wire is wrapped around an iron core.

1. I will connect the wire to the power pack and set the voltage to 8. I will then switch the power on.

2. I will now attempt picking up paper clips using no turns in the wire and will record the result.  

3. I will repeat this procedure but increase the turns in steps of 5, up to 40.

After carrying out a preliminary experiment the wire we were using was only able to wrap around the iron core 40 times.  We decided to go up in steps of 5 so that the electromagnet was not too strong or too weak to pick up the paper clips.

Safety Precautions

While doing this investigation we need to be aware of any safety precautions.  As we are working with electricity we must make sure the voltage is not set too high as the wire may over heat and will melt on to hands causing burns to the skin.

Prediction

I predict that the more coils wrapped around the iron core the stronger the electromagnet will become resulting in more paper clips being picked up.  I know this because it says in ”GCSE Success Double Award Physics Higher” that to make the magnet field stronger we can increase the current or make the wire into a coil.  It also says that if a solenoid is wrapped on to a core made from material such as iron, the strength of its magnetic field increases.  From this information I can predict that the amount paper clips picked up depends on the number of coils that are wrapped around the iron core, the voltage and the strength of the iron core.  If any of these factors change then the test will not be fair.  

We also know that the electricity from the power pack and the movement within the wires creates magnetism.  As we know, you need two of the above three things to create the third:-

Movement

         

Electricity                                Magnetism

So when the movement from the coil and the electricity  flowing from the power packs creates magnetism in the iron core.

Main Factors

The main factors in my investigation are the voltage, the iron nail and the number of coils.  The voltage, iron nail and the wire must be kept constant to ensure a fair test.  I will be varying the number of coils that will be wrapped around the iron core.

Obtaining Evidence

First Experiment

Second Experiment

During the investigation no changes were made to our plan but we repeated the experiment support our results.

Analysing Evidence

From my final set of results I have found out that they do not support my original prediction.   The amount of paper clips that were picked up did not increase as the number of coils increased.  For example

15 coils         41 paper clips

        The amount of paper clips

25 coils        38 paper clips        picked up has decreased

I predicted that the more coils around the iron core the more paper clips that will be picked up.  My graph shows on average a slow increase but a pattern formed where for every increase there was also a decrease in some situations.