Aim: To investigate the factors affecting the e.m.f. induced in a coil due to a varying magnetic field in a neighboring coil.
Extracts from this document...
Introduction
Physics Formal Lab Report
Name: Yip Ka Man
Class: 6B
Class number: 31
Date: 16th April, 2008
Experiment number: C17
Aim:
To investigate the factors affecting the e.m.f. induced in a coil due to a varying magnetic field in a neighboring coil.
Apparatus:
1 CRO (dual trace)
1 Signal generator
1 Search coil (axial type)
2 Square solenoids (different sizes)
1 d.c. power supply
1 Light-beam galvanometer
1 a.c. ammeter
1d.c. ammeter
1 Rheostat
2 PVC-covered copper wire 26 s.w.g. (2 m long)
1 Magnetic field board
1 Stop watch
Connecting leads
Theory:
The electromagnetic induction is a phenomenon that a varying magnetic flux can induce an electromotive force (e.m.f.) in a coil. The induced e.m.f. depending on several factors can be described by the Faraday’s Law of Electromagnetic Induction:
Induced e.m.f. (ε) = -dΦ/dt
Where Φ is the magnetic flux enclosed by a one-turn-coil. Note that the negative sign denotes that the induced e.m.f. and induced current oppose the original change of magnetic flux.
If the magnetic flux linked with a coil of area A, having N turns and at right angles to the magnetic field of flux density B, the total magnetic flux (Φ) is NBA. Hence,
Induced e.m.f. (ε) = -NAdB/dt
Procedures:
A. Rate of change of magnetic flux
Middle
- A graph of the induced e.m.f. (ε) against the number of turns (N) was plotted.
B. Number of turns of coil
- Steps 3 to 4 were repeated with the other values of numbers of turns of the copper coil around the solenoid. The results were tabulated.
No. of turns(N) | 5 | 7 | 9 | 11 | 13 | 15 |
Induced e.m.f.(ε)/mV | 0.04 | 0.05 | 0.06 | 0.07 | 0.08 | 0.09 |
- A graph of the induced e.m.f. against the number of turns was plotted.
C. Cross-sectional area of coil
- Two square solenoids of different cross-sectional areas were connected in series to the signal generator. The solenoids both had the same number of turns per unit length but one had a larger cross-sectional area than the other.
- 10 turns of the copper wire were wired tightly around the middle of each solenoid. One copper wire was connected to channel 1 of a dual trace CRO and the other to channel 2. The solenoids were kept well apart from each other.
- The signal generator was turned on and set to 1 kHz. The CRO setting was adjusted to display both whole traces on its screen.
- The time base of the CRO was switched off. The length of the vertical trace shown on the CRO was recorded, which represented the induced peak-to-peak e.m.f. in the copper coil for each solenoid.
Solenoid | Large | Small |
Induced e.m.f.(ε)/mV | 130 | 80 |
Conclusion
-There is reaction time of an individual.
-A stopwatch which is fast.
-The surrounding magnetic field of the neighboring solenoids may affect the experimental result.
-The setting and calibration of the CRO is wrong.
Suggested improvements:
-Repeat the experiment several times and take the average data for calculation.
-The time measured by a stopwatch is checked using another watch.
-Place the neighboring solenoids perpendicular to each other.
-Reset the setting and calibration of the CRO.
Conclusion:
From the experiment, it is observed that the factors affecting the e.m.f. induced in a coil due to a varying magnetic field in a neighboring coil are the rate of change of magnetic flux, the number of turns of coil and the cross-sectional area of coil.
This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.
Found what you're looking for?
- Start learning 29% faster today
- 150,000+ documents available
- Just £6.99 a month