ee lab report(final)

Faraday’s law experiment 2013

4.0 Results and discussions

4.1 Part A:

-By taking figure 2 experimental setup as reference, the direction of B is outside the

page and the direction of potential ФAirgap is negative when the current is positive and

decreasing. The direction of B is into the page and the direction of potential ФAirgap is

negative when the current is negative and increasing. The direction of B is outside the

page and the direction of potential ФAirgap is postive when the current is negative and

decreasing.

- According to Lenz’s Law, it states that the direction of the induced electromotive force

(emf) is always opposing the change in magnetic flux producing it. When static current

is used, this means that the current is not changing with the time due to the flow of

electric charge is only in one direction. Hence, the potential ФAirgap will be zero and

there will be no direction of B because the current is not changing and thus there is no

induced emf as well as magnetic charges.

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Figure 1: Geometry of twisted wire pair of problem Q4.

a) The direction of surface in loop 1 is clockwise and inside the page. The direction of

surface in loop 2 anti-clockwise and outside the page. Due to the direction of flux of loop

1 and loop 2 are opposite. While passing by with each other, the flux will be cancelled

out. Hence, the net flux is equals to zero.

b) Twisted wires will be used in the experiment because it will help to prevent

electromagnetic interference from external sources and crosstalk from external wires.

The interference will be decreases because the loop area between wires is reduced.

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c) If parallel wires are used instead of twisted wires, the parallel wires will carry

currents that will exert forces to each other. The force is attractive if the current goes

the same way in both wires. If the currents are on the opposite direction for both wires,

the force will be repulsive instead. By using parallel wires, one of the wires will set up

magnetic field and then another wire will be influenced by the magnetic field. Crosstalk

such as noise and interference will occur. Moreover, parallel wires only include low

bandwidth that can be transmitted. Hence, if parallel wires are used instead of twisted

wires, there will be electromagnetic interference and noise occurs.

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4.2 Part B: (Experiment): The experimental setup and the layout are shown in figure 3 and figure 4. Please make sure that the connections are as shown in figures 4.

Experimental Results

Table 1: Experimental value for loop 1

Frequency (kHz) Measured ɸ (mv) Phase shift (deg)10 7.65 92.1620 10.75(expected value

= about 10.6)86.40

50 18.75 93.60100 31.25 95.04200 55.00 96.48500 98.00 95.401000 221.50 93.60

For loop 1, it has 4 sides and performs for only 1 turn.

Table 2: Experimental value for loop 2

Frequency (kHz) Measured ɸ (mv) Phase shift (deg)10 9.84 86.4020 12.6 90.4250 21.8 88.20100 36.2 92.16200 63.1 92.16500 112.0 90.001000 268.00 92.16

For loop 2, it has 4 sides and performs for 2 turns.

Theoretical results

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Table 3: Theoretical value of potential air gap for loop 1

Frequency (kHz) Theoretical ɸ (mv) Phase shift (deg)10 3.67 9020 7.35 9050 18.37 90100 36.74 90200 73.48 90500 183.7 901000 367.4 90

For loop 1, it has 4 sides and performs for only 1 turn.

Table 4: Theoretical value of potential air gap for loop 2

Frequency (kHz) Theoretical ɸ (mv) Phase shift (deg)10 4.40 9020 8.84 9050 22.08 90100 44.18 90200 88.36 90500 220.88 901000 441.78 90

For loop 2, it has 4 sides and performs for 2 turns.

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Comparison between experimental and theoretical results for loop 1 and

loop 2.

For loop 1,

Frequency (kHz)

Experimental ɸ (mv)

Theoretical ɸ (mv)

Experimental Phase shift

(deg)

Theoretical Phase shift

(deg)10 7.65 3.67 92.16 9020 10.75 7.35 86.40 9050 18.75 18.37 93.60 90100 31.25 36.74 95.04 90200 55.00 73.48 96.48 90500 98.00 183.7 95.40 901000 221.50 367.4 93.60 90

For loop 2,

Frequency (kHz)

Experimental ɸ (mv)

Theoretical ɸ (mv)

Experimental Phase shift

(deg)

Theoretical Phase shift

(deg)10 9.84 4.40 86.40 9020 12.6 8.84 90.42 9050 21.8 22.08 88.20 90100 36.2 44.18 92.16 90200 63.1 88.36 92.16 90500 112.0 220.88 90.00 901000 268.00 441.78 92.16 90

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Question: What is the percentage error for potential airgap of

this experiment?

By taking frequency value of 10 KHz,

For loop 1,

Percentage error = ¿ Experimental value – theoretical value∨¿

Theoretical value¿

x100%

= ¿7.65−3.67∨ ¿3.67

x 100 %¿

= 108.40%

For loop 2,

Percentage error= ¿ Experimental value – theoretical value∨¿

Theoretical value¿

x100%

=¿9.84−4.40∨ ¿4.40

¿ x 100%

=123.46%

Note: For loop 1 and loop 2, the experimental and theoretical value of the potential

airgap is very big. This might cause by the current value does not constantly maintain

at 0.05A during the laboratory session. The other source of error might be due to

calibration error of the oscilloscope.

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Question: What is the percentage error for phase shift of this

experiment?

By taking frequency value of 10 KHz,

For loop 1,

Percentage error = ¿ Experimental value – theoretical value∨¿

Theoretical value¿

x100%

= ¿92.16−90.00∨ ¿90.00

x100 % ¿

= 2.4%

For loop 2,

Percentage error= ¿ Experimental value – theoretical value∨¿

Theoretical value¿

x100%

=¿86.40−90.00∨ ¿90.00

¿ x 100%

= 4.0%

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Question: Why loop 2 should perform for 2 turn?

Answer: For loop 2, the circuit is performed for 2 turns because the area for loop 2 is a

portion of loop 1. The area of loop 1 is (460mm x 460mm) = 211600 mm2 = 0.2116m2, the

area of loop 2 is (400mm x 400mm) = 160000 mm2 = 0.16m2. The area of loop 1 is almost

twice the area of loop 2. Hence, the value of Vloop2 should be multiply by 2 so it is nearer

to the value of Vloop1 in order to do comparison.

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In this experiment, practically, my partner and I have learnt how to setup

the experiment layout by using soldering and connecting the twisted wires

to the AC oscilloscope. Moreover, my partner and I also learnt how to

observe the AC waveforms shown on the oscilloscope to obtain phase shift

and the value of potential airgap, ɸ. By referring to theory, my partner and

I have learnt new knowledge application of Faraday’s law and Lenz’s law

on magnetic field. Basically, Faraday’s law is referring to basic law of

electromagnetism that the emf induced in the loop should be proportional

to the rate of change of magnetic flux through it. By applying the Faraday’s

law formulae, the voltage over the loop which is known as electromagnetic

force (emf) can be calculated. Furthermore, I also learnt the application of

Lenz law on magnetic field. Generally, Lenz’s law states that the induced

emf and current will be in a direction such that the induced magnetic field

opposes the original magnetic flux change. The induced current will

produce an induced magnetic field. The magnetic field will be opposing the

direction of the changing flux. The lenz’s law can be used to determine the

induced emf direction of the loop. Besides that, I also learn how to derive

the formulae of induced emf regarding Faraday’s law and perform

theoretical calculation for loop 1 and loop 2. Finally, the results for both

experimental and theoretical results for loop 1 and loop 2 have been

compared and contrast for further understanding.

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ee lab report(final)

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