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# electomagnet lab

Extracts from this document...

Introduction

Siddharth Nair

10 C

PHYSICS LAB REPORT

STRENGTH OF AN ELECTROMAGNET

AIM:

To investigate the factors that affects the strength of an electromagnet.

THEORY:

An electromagnet is a magnet that runs on electricity. Unlike a permanent magnet, the strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. The poles of an electromagnet can even be reversed by reversing the flow of electricity.

An electromagnet works because an electric current produces a magnetic field. The magnetic field produced by electric current forms circles around the electric current, as shown in the diagram below:

If a wire carrying an electric current is formed into a series of loops, the magnetic field can be concentrated within the loops. The magnetic field can be strengthened even more by wrapping the wire around a core. The atoms of certain materials, such as iron, nickel and cobalt, each behave like tiny magnets. Normally, the atoms in something like a lump of iron point in random directions and the individual magnetic fields tend to cancel each other out. However, the magnetic field produced by the wire wrapped around the core can force some of the atoms within the core to point in one direction. All of their little magnetic fields add together, creating a stronger magnetic field.

As the current flowing around the core increases, the number of aligned atoms increases and the stronger the magnetic field becomes. At least, up to a point. Sooner or later, all of the atoms that can be aligned will be aligned. At this point, the magnet is said to be saturated and increasing the electric current flowing around the core no longer affects the magnetization of the core itself.

FACTORS AFFECTING THE STRENGTH OF AN ELECTROMAGNET:

• Distance between each turn of the coil: If the distance between two turns in the coil of a solenoid is decreased, the electromagnetism increases. This is because; the air trapped between two turns forms an insulating barrier that doesn’t allow the passage of current, if the distance was more.
• Strength of the electric current: To make an electromagnet function correctly electricity has to be passed through it. Therefore if the current is increase the strength of the magnet will increase and vice versa.
• Number of turns of the coil: If the number of turns on the solenoid is increased then the strength of the magnet is increased and vice versa.

ROUGH PLAN:

Above I have already described the three factors that affect the strength of the magnet. Therefore in this experiment I will investigate only 2 of the factors and see the effect it has on the strength of the magnet. The two factors are:

1. Number of turns of the coil.
2. Strength of the current

For the first experimental factor I planned to wrap a wire around the electromagnet and then pass current through it and then see how many nails it attracts. I will keep reducing the number of turns and then see the effect on the nails it has.

For the second experimental factor, I will again make an electromagnet by  wrapping the wire around the iron core. Therefore in this I will see by varying the current how much of the mass is attracted to the electromagnet.

BASIC SET-UP OF THE APPARATUS:

APPARATUS:

• Power pack
• Piece of iron
• Sand paper
• Metre- rule
• Clamp stand
• 20 iron nails/ paper clips
• Digital balance
• 30cm of copper wire.
• A long iron nail
• Small Petri dish
• Plastic cup

FACTOR 1: NUMBER OF TURNS OF THE COIL

HYPOTHESIS:

According to theory to make a solenoid a wire is to be wrapped around a coil and current has to be passed therefore an electromagnet is made. There my hypothesis is that by increasing the number of turns the electromagnetism will increase.

GRAPH OF EXPECTED RESULTS:

VARIABLES:

Constant:

• strength of current passed
• distance between each turn
• surroundings
• equipment

Independent:

• number of turns

Dependent:

• number of iron nails attracted

FAIR TEST:

• The strength of the current passed should be the same for every trial. This can be done by keeping the wire plugged into the same voltage of the power pack for each trial.
• The equipment used in the experiment should remain the same so that the margin of errors is the same.
• The wire should be uniformly thick throughout its length.
• If the nails are rusted, they should be rubbed with sand paper and weighed again so that the new mass is taken into account.
• While wrapping the wire around the piece of iron, one must make sure that the distance between each turn is equal and this distance should be very less to prevent the air from acting as an insulating barrier.
• The distance between the iron nails and the electromagnet should be kept constant to reduce the margin of error.
• It should be made sure that there are no other magnets nearby so that it does not interfere with the experiment and cause anomalies in the experiment.

SAFETY PRECAUTIONS:

• The power pack must be powered on only after everything has been plugged in correctly. One must check the whole set-up at least twice before powering it on.
• The conducting wires must be insulated very well so that one doesn’t get a shock due to any bare wire.
• Make sure that there is no water spilt anywhere around the power pack because water is a good conductor of electricity.
• Rusted iron nails should be handled with care so that they don’t poke the body. If they do, one must immediately get a tetanus vaccine.
• The entire wire should be insulated excluding the part that is connected ti the power supply.
• A pure iron nail should be used to make sure that the nail does not retain its magnetism.

MODIFICATIONS:

• The clamp stand was not used because the length of the wires in the circuit was too less to be suspended from the clamp stand.
• The power pack was not able to give a high current to the circuit and it was very less to make the iron nail a strong electromagnet. Thus, the small iron nails were not being attracted and so iron filings having a less mass were used for the experiment.
• A plastic cup was used to collect the iron filings that fall after the power is turned off.
• It was not possible to use a piece of iron for the experiment since it was not available in the lab. Therefore, I used an iron nail for my experiment.

Middle

Weigh the plastic cup and record its mass in the raw data table.In a Petri dish, place some iron filings. It is not necessary to record their mass.Wrap the non- insulated wire to the long iron nail certain number of times to make it a temporary electromagnet.After making the desired number of turns, the wire should be attached to another insulated wire using crocodile clips.While wrapping the insulating wire, care should be taken that there is no space left between any of the turns.Hold up the apparatus using two insulated ends of the conducting wires.The iron filings must be placed exactly below the electromagnet.One must make sure that the distance between the surface of the desk (where the nails/clips are kept) and the suspended electromagnet is very small. This is so that the filings get attracted more easily to the electromagnet.After checking and re-checking that everything has been set up correctly, the power supply must be turned on for two minutes.The electromagnet must be held over the iron filings kept inside the Petri dish using the two insulated ends of the crocodile clips which are attached to the insulating wire.Just before two minutes, the plastic cup must be placed below the electromagnet so that the iron filings which will fall when the power is turned off can be collected.After about two minutes, the power must be switched off and the plastic cup in which the iron filings have fallen back due to demagnetisation of the iron core should be removed from below the suspended electromagnet.The plastic cup should be re-weighted to see the change in the mass because of the iron filings.(mass of plastic cup + iron filings)- (mass of plastic cup)

Conclusion

For the results obtained without using the iron core, the graph again shows a positive relationship. Therefore my hypothesis is also right as, as I increased the current the mass of the nails attracted increased.

SUGGESTED IMPROVEMENTS:

• The experiment could have been done again and therefore more results could be obtained.
• The distance between each of the turns could have been accurately measured to see if it was kept constant.
• More trials could have been taken to get a clearer trend for the graphs and a better relationship in the results.

SOURCES OF ERRORS:

• The current to the magnet was not accurately supplied according to the given specific value. This could have also affected the magnetization.
• The distance between each turn may not have been equal and this would have also affected the strength of the magnet.
• The wire was not tightly wrapped around the whole iron nail because it was very firm and it took a lot of effort to make the turns manually.
• When the current supply was stopped some of the iron filings were stuck to the iron nail and could not be removed.

CONCLUSION:

After performing the experiment successfully it is verified and proved that my hypotheses were right. Therefore as you increase the number of turns on the coil the strength of the magnet increases and therefore more mass of nails are attracted. Also my other hypothesis was proved right which was that as the strength of the current would be increased the strength of the magnet would also increase. Therefore my experiment was successful and therefore all my hypotheses were proved right.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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## Here's what a star student thought of this essay

3 star(s)

### Response to the question

The facts in this experiment are good, but the analysis is largely missing. You have demonstrated well every step of this experiment. You have detailed your pre-experiment hypothesis and analysed your findings and compared them to your original findings in ...

### Response to the question

The facts in this experiment are good, but the analysis is largely missing. You have demonstrated well every step of this experiment. You have detailed your pre-experiment hypothesis and analysed your findings and compared them to your original findings in the second experiment, but nothing in the first section. There is not enough analysis in the analysis section for either experiment let alone both. You need to talk about errors, the cause of errors, and the science behind proving your hypothesis. More appropriate diagrams could help add to the text.

### Level of analysis

You have successfully proven your initial theory, but you need more proof Ã¢â‚¬â€œ which can be obtained from the results you have already gathered; however, it would improve the reliability of your results by repeating your experiment and taking an average of the results and adding error bars to your graph. This would also help explain why your points do not exactly lie on the line of best fit if they are inside the error range. Without analysis of the errors, it does not show you understand the experiment as well as you should.

### Quality of writing

While the piece is of a high standard, a few sections would benefit from being rewritten, such as the final conclusion. Phrases such as Ã¢â‚¬Å“very lessÃ¢â‚¬Â in the factor 1 - fair test section should be the focus of this. Technical terms are used sparsely, but are always used well and add to the piece. More technical language could be added, but it shouldnÃ¢â‚¬â„¢t be a cause for concern if left as it is.

Reviewed by pratstercs 29/02/2012

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