Assessment Task #1 physics

MARCELLIN COLLEGE RANDWICK - HSC PHYSICS

Topic: Motors & Generators

Andrew JacksonHSC Practical Investigation • Marcellin College • 25 November 2011

Andrew Jackson • email: [email protected] • Marcellin College

1

mailto:[email protected]

Table of Con-tents

Background Theory 1

Aim 1

Hypothesis 1

Apparatus 1

Variables & Hazard Analysis 1

Hazards 1

Procedure Recount 1

Phasellus et ligul 1

Results 1

Analysis 1

Error Analysis 1

Hasellus et ligul 1

Conclusion 1

The relative motion between the coil and the magnet is varied: 1

Discussion 1

Hasellus et ligul 1

Andrew Jackson • email: [email protected] • Marcellin College

1

mailto:[email protected]

Background TheoryInsert Subtitle Later

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The ancient Greeks from Magnesia discovered stones called lodestones that were naturally magnetised. In 1819 Hans Christian Oersted, a Danish physicist and chemist established a link between magnetism and current when he observed a compass needle deflected when placed near a current-carrying wire, and reasoned that the wire must produce a magnetic field around it. Michael Faraday a British chemist and physicist studied this phenomenon and was the first person to realise that a changing magnetic field was able to produce electricity (electromagnetic induction). He mapped the magnetic field generated around the current carrying wire in 1821. In one of his later experiments, he achieved the induction of a current in a conductor through the application of a changing magnetic field. Faraday showed that moving a magnet near a coil could generate an electric current in the coil and when the mag-net is turned around, the galvanometer needle deflects in the opposite direction, thereby discovering that the magnitude of the current depends on the rate of move-ment of the magnet: the faster it is moving in and out of the coil the larger the cur-rent. This was called electromagnetic induction, created due to a change in magnetic flux through a conductor. This breakthrough led to further work and discoveries in the electromagnetism field and the development of electric generators and subse-quent use of electricity for lighting and the many other electrical appliances in use to-day. Society is currently reliant on technology to a much larger extent than ever be-fore and with the increase in technological devices there has been a steady growth in the rate of many cancers. Past studies discovered very small increases in these can-cers; however more recent, well-conducted studies are revealing alarming increases in the association of EMFs with leukaemia, brain tumours and breast cancer necessi-tating further studies of EMFs and the effects on humanity.

AimInsert Subtitle Later

To investigate the effect on a generated current when:

• The distance between the coil and magnet is varied

• The strength of the magnet is varied.

• The relative motion between the coil and the magnet is varied

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HypothesisPhasellus ut arcu ut nulla dignissim auctor

It was hypothesised that:

When the distance between the coil and magnet is increased, the amount of current

generated will decrease when the numbers of coils in the solenoid, the size of the so-

lenoid and the size/shape of the magnet is maintained at a constant value, and vice

versa for when the distance between the coil and magnet is decreased.

When the strength of the magnet is varied, the amount of current generated will in-

crease when the numbers of coils in the solenoid, the size of the solenoid and the

size/shape of the magnet is maintained at a constant value, and vice versa for when

the strength of the magnet is decreased.

When the relative motion between the coil and magnet is increased, the amount of

current generated will decrease when the numbers of coils in the solenoid, the size of

the solenoid and the size/shape of the magnet is maintained at a constant value, and

vice versa when the relative motion between the coil and magnet is decreased.

Faraday’s law logically supports this hypothesis as it indicates that any change in the

magnetic environment of a coil of wire will cause a voltage (EMF) to be "induced" in

the coil. Due to magnets possessing a magnetic field, a moving magnet should disrupt

the magnetic environment of the solenoid, thereby producing a current, and the fact

that Faradays law is a valid and well settled theory leads to the conclusion that the

hypothesis will be supported through the practical experiment.


ApparatusInsert Subtitle Later


The following materials are prerequisites in order to conduct this first-hand investiga-

tion:

• Three identical bar magnets

• A solenoid

• An ammeter / galvanometer

• A ruler

• Two wires.

• A metronome

Variables & Hazard AnalysisPhasellus ut arcu ut nulla dignissim auctor

Due to this experiment having three separate components, there are three sets of variables.

The distance between the coil and magnet is varied:

• Independent - The distance between the coil and the magnet

• Dependent - The amount of current generated

• Controlled - Number of coils in solenoid

- Size of the magnet

- Shape of the magnet

- Size of the solenoid

The strength of the magnet is varied:

• Independent - The strength of the magnet

• Dependent - The amount of current generated





The relative motion between the coil and the magnet is varied:

• Independent - The relative motion between the coil and the magnet

• Dependent - The amount of the current generated





Hazards

Nullam tortor. Fusce malesuada. Quisque dolor mauris, malesuada quis, ultricies non,

interdum blandit, lectus. Etiam nulla lacus, nonummy a, blandit sed, pellentesque

eget, arcu. Phasellus id pede. Vivamus tortor nibh, tempus auctor, interdum a, fau-

cibus ut, mi. Aliquam tincidunt turpis eleifend orci. Mauris at odio vel metus ullam-

corper blandit. Nullam tortor. Fusce malesuada. Quisque dolor mauris, malesuada

quis, ultricies non, blandit, lectus. Etiam nulla lacus. Etiam nulla lacus, nonummy a,

blandit sed, pellentesque eget, arcu. Phasellus id pede. Vivamus tortor nibh, tempus

auctor, interdum a, faucibus ut, mi. Aliquam tincidunt turpis eleifend orci. Mauris at

odio vel metus ullamcorper blandit. Mauris at odio vel metus ullamcorper blandit.

Nullam tortor. Fusce malesuada. Quisque dolor mauris.

Procedure RecountPhasellus ut arcu ut nulla dignissim auctor


Phasellus et ligul

1. A circuit was constructed, consisting of a solenoid, two wires and a Gal-

vanometer.

2. To measure the effect on a generated current when the distance between the

magnet and the coil is varied, one magnet was placed directly next to the solenoid

with the north end of the bar magnet facing towards the solenoid. Then the bar

magnet was quickly withdrawn away from the solenoid.

3. Any movement of the needle of the galvanometer was recorded.

4. Then the magnet was placed 1.5 cm from the solenoid and moved in the same

fashion as before.

5. Any movement of the needle of the galvanometer was recorded.

6. The magnet was then placed 3 cm away from the solenoid and withdrawn

swiftly.

7. Any movement of the needle of the galvanometer was recorded and the re-

sults were compared to verify effects on a generated current when the distance

between the magnet and coil is varied.

8. To measure the effect on a generated current when strength of the magnet is

varied, one magnet was placed inside the solenoid and swiftly removed.

9. The movement of the needle on the ammeter was recorded.

10. Two magnets with the two north poles connected and the two south poles

connected were then placed inside the solenoid and quickly withdrawn.

11. The movement of the needle on the ammeter was recorded.

12. Three magnets were then connect in the same manner as step 10, placed in-

side the solenoid and quickly withdrawn.

13. The movement of the needle on the ammeter was recorded and compared

with the other results to verify the effects on a generated current when the

strength of a magnet is varied.

14. Through the use of a metronome set to a tempo of 120, one magnet was

moved back/forth every beat.

15. The movement of the needle of the galvanometer was recorded.

16. The metronome was then set to a tempo of 250 and the magnet was moved

back and forth every beat.

17. The movement of the needle of the galvanometer was recorded.

18. The metronome was then set to a tempo of 30 and the magnet was moved

back and forth every beat.

19. The movement of the needle of the galvanometer was recorded and com-

pared with the other results to verify the effect on a generated electric current

when the relative motion between the coil and the magnet is varied.

ResultsPhasellus ut arcu ut nulla dignissim auctor

Distance

Displacement from

the solenoid (cm)

0 1.5 3

1st test (µa) -4 -2 -1

2nd test (µa) -4 -2 -1

3rd test (µa) -4 -2 -1

Strength

Number of mag-

nets used simulta-

neously

1 2 3

1st test(µa) -4 -12 -18

2nd test (µa) -4 -12 -18

3rd test (µa) -4 -12 -18

Motion

Beats Per Minute

(bpm)

120 250 30

1st test(µa) -2 to 2 -1 to 1 -4 to 4

2nd test (µa) -2 to 2 -1 to 1 -4 to 4

3rd test (µa) -2 to 2 -1 to 1 -4 to 4

AnalysisPhasellus ut arcu ut nulla dignissim auctor

Whilst the experiment was being performed, the results gathered were organised

into multiple tables. Through the tables, the results were correlated in order to ver-

ify the hypothesis. The results demonstrated that:

• As the distance between a magnet and the solenoid increased, the amount of

current generated in the coil was reduced.

• As the strength of the magnet increased, the amount current generated in the

coil increased.

• As the relative motion between the magnet and the solenoid increased, the

amount of current generated decreased.

Error Analysis

You will need to undertake an error analysis. This could be as simple as a qualitative description or as complex as a full numerical error calculation. However, it is the logic that is important and some quantification of accuracy should be evident. Consult a text to find out the way to do it.

Heinrich Emil Lenz put a definite direction to induced currents when the magnetic

flux was changing.

"The Induced current is such as to oppose the change in the applied field."

Whenever there is a change in the number of magnetic field lines passing through a loop of wire, a voltage (or electromotive force) is generated (or induced) in the loop of wire. This is how an electric generator works. The phenomenon is known as elec-tromagnetic induction and is explained by Faraday's law of induction:

e = - dF / dt

where e


Lasellus ut arcu ut nulla dignissim auctor. Etiam sed elit sed diam tempus con-

sectetuer. Proin dignissim, velit a gravida elementum, metus tellus dictum mauris,

quis auctor est lectus in sapien. Fusce diam arcu, ultricies non, ullamcorper feugiat,

semper quis, tortor. Phasellus egest feugiat augue. Vestibulum nec wisi. Vivamus la-

cus wisi, tincidunt qui.

ConclusionPhasellus ut arcu ut nulla dignissim auctor

The distance between the coil and magnet is varied:

• The closer the magnet, the stronger or the more larger electromotive force

produced and as a result the larger the current produced.


The strength of the magnet is varied:

• The stronger the magnet, the more movement in the needle occurs because

the stronger the magnet, the higher the magnetic flux density via the magnetic flux

strength. Therefore more flux lines pass through a given area and thereby increas-

ing the magnetic flux density.

The relative motion between the coil and the magnet is varied:

• The faster the magnet is moved, the more magnetic flux lines are being cut.

Therefore a larger EMF is being produced and thereby a stronger current.

DiscussionPhasellus ut arcu ut nulla dignissim auctor

Explanation of the strengths and weaknesses of the experiment; discussion of accu-

racy, validity and reliability of results; modifications to experiment are recom-

mended; explanation of possible sources of variation are included

The experiment performed provided a clear illustration of Faraday’s law. However,

there were many aspects of the experiment that could have been altered in order to

reduce/remove error:

• In order to reduce inaccurate readings of the galvanometer, a digital gal-

vanometer should be used to reduce human error.

• A method of removing the magnet from the area of the solenoid at the same

velocity for all repetitions of the experiment should be used to remove human er-

ror.

The experiment was valid as it correctly tests the hypothesis by experiment the effect

on a generated current when the distance between the coil and magnet is altered,

the strength of the magnet is altered and the relative motion between the coil and

magnet is altered.

The experiment was reliable as it underwent multiple repetitions in order to achieve

reliable results and verify the hypothesis.

The experiment was accurate as it ...


Lasellus ut arcu ut nulla dignissim auctor. Etiam sed elit sed diam tempus con-

sectetuer. Proin dignissim, velit a gravida elementum, metus tellus dictum mauris,

quis auctor est lectus in sapien. Fusce diam arcu, ultricies non, ullamcorper feugiat,

semper quis, tortor. Phasellus egest feugiat augue. Vestibulum nec wisi. Vivamus la-

cus wisi, tincidunt qui.

Hasellus et ligul

Nullam tortor. Fusce malesuada. Quisque dolor mauris, malesuada quis, ultricies non,

interdum blandit, lectus. Etiam nulla lacus, nonummy a, blandit sed, pellentesque

eget, arcu. Phasellus id pede. Vivamus tortor nibh, tempus auctor, interdum a, fau-

cibus ut, mi. Aliquam tincidunt turpis eleifend orci. Mauris at odio vel metus ullam-

corper blandit. Nullam tortor. Fusce malesuada. Quisque dolor mauris, malesuada

quis, ultricies non, blandit, lectus. Etiam nulla lacus. Etiam nulla lacus, nonummy a,

blandit sed, pellentesque eget, arcu. Phasellus id pede. Vivamus tortor nibh, tempus

auctor, interdum a, faucibus ut, mi. Aliquam tincidunt turpis eleifend orci. Mauris at

odio vel metus ullamcorper blandit. Mauris at odio vel metus ullamcorper blandit.

Nullam tortor. Fusce malesuada. Quisque dolor mauris.

What needs to be done

- Analysis: Error analysis

- Discussion: Explanation of possible sources of variation; accuracy

- Variables and Hazard Analysis: Hazards

- Bibliography

Documents

Assessment Task #1 physics