To find out how the positioning of a solenoid (wire that has been coiled) on a metal core (iron core in our case) affects the strength of an electromagnet

Method: After all the apparatus is collected a 30 cm long copper wire has to be equally coiled around the iron core (tightly) to form a solenoid (3 times in the middle, 3 times right than left). Then the solenoid will be connected to the power supply (9V), however with an ammeter in series and a voltmeter in parallel to the battery (see Fig. 1.2) to control two of the constants. After that a sheet of paper with iron filings equally spread over it will have to be prepared. Then the solenoid connected to the power supply, voltmeter and ammeter has to be placed very carefully on top of the sheet of paper with the iron filings (but the iron core with the solenoid has to be parallel to the sheet of paper with the iron filings so the contact area between the solenoid and the iron filings is the same throughout all the nine experiments). Then after ten seconds the solenoid has to be picked up with the iron filings it has collected and placed a few centimetres above the balance (making sure the solenoid is not disconnected from the power supply). Only after that, the solenoid can be detached from the power supply since then the iron core with the solenoid will lose its magnetism and drop the iron filings on top of the balance. Then the reading from the balance will have to be recorded in a table as well as the ammeter readings and the voltmeter readings (voltmeter and ammeter readings have to be made while the power supply is connected). Each experiment (Middle, Right and Left) has to be done 3 times so in other words 9 experiments in total to receive a reliable and variety set of results.

Diagram:

Fig. 1.2

Fig. 1.3

List of Equipment:

> Power Supply

> Balance (Top pan)

> Ammeter (digital)

> Voltmeter (digital)

> 2 grams of Iron Filings

> Copper Solenoid (copper wire coiled around)

> Iron Core

> Sheet of Paper

> Crocodile Clips

Safety:

Since in the following experiment we are dealing with electricity some very important safety measures have to be kept in mind at all times.

. While connecting the apparatus always check if the power supply is turned off.

2. Too much electricity is dangerous because it might cause the equipment to over load causing it to burn or making the circuit wires start to melt.

3. Always wear safety goggles and be attentive all the time during the actual experiment.

4. Always connect the ammeter in series because if connected in parallel then it will overheat (depending on its resistance) and start to burn.

Results:

Fig 1.4

Positioning of the Solenoid

Middle

Left

Right

Mass of iron filings attracted in grams (g)

0.0190

0.0170

0.0190

Mass of iron filings attracted in grams (g)

0.0190

0.0190

0.0190

Mass of iron filings attracted in grams (g)

0.0185

0.0190

0.0185

Mass of iron filings attracted in grams (g)

0.0185

0.0175

0.0180

Mass of iron filings attracted in grams (g)

0.0185

0.0190

0.0180

Average Mass of Iron filings in grams (g)

0.0187

0.0187

0.0185

Average Current in Amps (A)

2+

2+

2+

Average Voltage in Volts (V)

3

3

3

Graphs:

Fig 1.5

Fig 1.6

Conclusion:

From the results obtained in this experiment, it becomes very clear that changing the positioning of the solenoid on the iron core has no effect on the electromagnet's strength. This is because from Fig 1.4, 1.5 and 1.6 the results show that there is hardly any significant change in the results. However when the solenoid is placed on the right hand side of iron core there is a slight change of 0.0002 grams of iron filing collected in comparison to the other two positions (middle and left hand side) but this change is quite insignificant. The voltage also remained the same throughout all the nine experiments (as expected) and was measured with a voltmeter since the power supply was set to 3 volts at all times and therefore was anyway a constant (the voltage was measured with a voltmeter eventhough it wasn't really needed because the power supply was set to 3V). From the results that were obtained for current a conclusion could not be drawn and there for it is difficult to say anything about current in this specific experiment. There was one set of results (Fig 1.4, Right hand side position) that was slightly anomalic (0.0002g) in comparison to the other results but this will be later on analysed in the evaluation.

I can conclude by saying that my hypothesis was correct since the results (except for current in Amps) received were as I thought they would be.

Evaluation:

As in most of the experiments there are always a few improvements that can be made to get even better and more reliable results than the ones obtained from the previous one. The first factor in this experiment that could be improved is that of the ammeter readings, since the ammeter that was used was first of all not digital and only went up to 2 amps (however for this experiment we were looking at a greater current than just 2 amps). So either a potentiometer /variable resistor (to decrease the current) or a digital ammeter could be used, which would display higher currents than just 2 amps. The second factor in this experiment that could be improved would be that of the coiling of the wire around the metal coil because the wires were supposed to be tightly wrapped around the coil so there would be a 1 mm space between the wires (the solenoid was made up of 25 loops of insulated wire). Not following this factor was the reason for slight anomalic results (see Fig 1.5) between the positions middle and right plus left and right because for the two sides (middle and left) one partner looped the wires around the metal core and for the other side (right) the second partner looped the wires around (obviously differently than the first partner) the metal core. The third factor that could be improved in this experiment would be that of the tape (to keep the solenoid in place), since this could have been measured (e.g. 4cm per experiment) because in this experiment the tape was not measured and therefore became an uncontrolled variable. It is very difficult to say whether the last position's (right) results were anomalic because of the third factor or simply because the balance might have been reset incorrectly since the difference between the right hand side position and the other two positions (middle and left) was just 0.0002 grams. If this experiment was to be done again then it would a good idea to have a closer look at the three factors mentioned above.

Altogether this was a successful experiment because not only was the aim met but also the hypothesis was proved to be correct and most of the results were also reliable except for perhaps that one set mentioned above.

Bibliography:

http://www.essaybank.co.uk/free_coursework/158.html

GCSE Double Science Physics Book - The Revision Guide

From the GCSE Double Science Physics HL Revision Guide

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Physics Investigation Ajitesh Ghose 10A