Strength of the electromagnet

Aim:

To investigate how different factors affect the strength of the electromagnet.

Introduction:

There are totally two factors that I am going to investigate in this experiment:

m F1: How the number of coils affects the strength of the electromagnet.

m F2: How a change in current affects the strength of an electromagnet.

Hypothesis:

m F1: I think as the number of coils increase the strength of the electromagnet would also increase.

m F2: I think as the current increases the strength of the electromagnet would also increase.

Variables:

m F1:

* Independent: Number of coils.

* Dependent: Distance at which compass needle deflects.(+/-0.05 cm)

· Constants: Current, diameter of the wire, temperature, same iron core.

m F2:

* Independent: Current (+/-0.01amps)

· Dependent: Distance at which compass needle deflects.(+/-0.05 cm)

· Constants: Number of coils, diameter of the wire, temperature, same iron core.

Apparatus:

* Power Supply

* Ammeter (±0.01amps)

* Electromagnets with different number of coils

* Plastic Ruler (±0.05cm)

* Plotting Compass

* Crocodile clip wires

* Rheostat

Procedure:

· Using crocodile clips connect the circuit in the following way:

· F1:

§ Take an iron nail and with the help of a nichrome wire, coil it around the nail 5 times.

§ Switch the circuit on and wait for a minute.

§ Note down the constant current.

§ Take the plotting compass and steadily place it close to the electromagnet and slide it away in a straight line till the needle deflects slightly to one side from its vertically straight position.

§ Place a ruler from the north pole of the electromagnet and note the distance where this deflection occurs. This where the magnetic field lines would approximately end, and hence more the distance more the field lines and greater the strength.

§ Repeat the steps above but with 10, 15, 20, 25, 30 and 35 coils.

§ For the same number of coils measure the distance of deflection 2 times for a second trial.

· F2:

§ Using the same circuit now adjust the variable resistor so that u have a current of 0.5amps flowing through the circuit.

§ Make the constant number of coils to be 10 coils.

§ Take the plotting compass and steadily place it close to the electromagnet and slide it away in a straight line till the needle deflects slightly to one side from its vertically straight position.

§ Place a ruler from the north pole of the electromagnet and note the distance where this deflection occurs. This where the magnetic field lines would approximately end, and hence more the distance more the field lines and greater the strength.

§ Repeat the steps above but with 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.5 amps.

§ For the same current record the distance two times for a second trial.

Raw Data Table

F1: Effect of the number of coils on the strength of the electromagnet.

Number of Coils of electromagnet

Distance of deflection from North Pole of the magnet(+/-0.01cm)

Trial 1

Trial 2

5

1.7

1.9

10

4.9

5.1

15

7.6

7.5

20

9.5

9.5

25

12.3

12.1

30

14.8

15

35

16.9

17.2

Constant Current

0.75 A

F2: How changing current affects the distance at which the needle deflects.

Current (+/-0.01A)

Distance from North Pole of the magnet(+/-0.05cm)

Trial 1

Trial 2

0.5

1.3

1.2

1.0

2.9

3.0

1.5

4.6

4.6

2.0

6.2

6.3

2.5

7.9

8.0

3.0

9.3

9.5

3.5

10.7

10.8

4.0

11.6

11.8

4.5

12.1

12.3

5.0

12.6

12.9

5.5

12.8

12.8

Constant No. of Coils

10

Processed Data Table:

The only processing that can be done in this experiment is to find the average distance for the investigations for both the trials and hence making it easier to make the graph.

F1: Effect of the number of coils on the strength of the electromagnet.

Number of Coils of electromagnet

Average Distance of deflection from North Pole of the magnet(+/-0.05cm)

5

1.8

10

5

15

7.55

20

9.5

25

12.2

30

14.9

35

17.05

Constant Current

0.75 A

F2: How changing current affects the distance at which the needle deflects.

Current (+/-0.01A)

Average Distance from North Pole of the magnet

(+/-0.05cm)

0.5

1.25

1.0

2.95

1.5

4.60

2.0

6.25

2.5

7.95

3.0

9.40

3.5

10.75

4.0

11.70

4.5

12.20

5.0

12.75

5.5

12.80

Constant number of coils

10

Now I will plot the graphs of both these averages.

Graph Analysis: (Graph at the End)

F1: As you can see the graph is proportionate. As the number of coils increases the strength of the electromagnet also increases. There is a positive co-relation and this can be proved by theory as well. As the number of coils increase, the magnetic field of each coil also increases and hence a larger magnetic field would cause the electromagnet to be stronger. There is only one anomaly in our results at 20 coils and this can be neglected as it is a very minor anomaly.

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F2: In this graph also we notice that there is a positive co-relationship and hence the current is proportionate to the strength of the magnet. As current in a circuit increases the strength of the magnet would also increase as the coil is provided with more charge and hence the field lines would be spread over a larger area and the strength would be larger. But in this graph after 4.0 amps the graph is no longer proportionate. This can be due to the large amount of heat generated in the wires causing more resistance and the value of current would have changed and hence the curve in the graph.

Conclusion:

Our hypothesis for both the factors was proven right by our graphs. Strength of an electromagnet is proportionate to the current and the number of coils in the solenoid. As the number of coils increase the area of the magnetic field lines also increases hence a stronger electromagnet is produced. It is the same for an increase in current. But after a certain current it becomes tough to maintain other constant factors like temperature which might cause inaccurate results.

Evaluation:

· We could have taken more trials to get better results.

· We could have used an insulated wire so that the wire won’t heat up so fast and it wouldn’t have changed our results.

· The current wasn’t always exact. It kept fluctuating hence it may have given inaccurate readings.

· The exact distance where the needle turned would be very tough to find out as it turns over a range of distance hence that may have given inaccurate results.

Fair Test:

* The distance between the coils was kept the same in all the trials.

* For the first experiment we kept the current constant so that we can fairly compare the results.

* For the second experiment we kept the number of coils the same so that we can fairly compare the results.

* And for both the experiments we kept the same material of the core and the wire.

Safe Test:

· As it was dealing with electricity we made sure we did not touch any open ends to prevent ourselves from getting a shock.

· Also we did not touch the wire right after the experiment was over as it may have been quite hot.