- Level: International Baccalaureate
- Subject: Physics
- Word count: 1439
Magnetic field around a conductor
Extracts from this document...
Introduction
Fredrik Hansen IB1A
IB Tingvallagymnasiet Karlstad
Physics Department
Fredrik Hansen
Mail: [email protected]
Laboratory experiment:
Magnetic Field around a Conductor
IB Physics Higher Level
laboratory experiment report
by Fredrik Hansen
class: IB1A
supervisor: Anna Malmberg
conducted: 2009-05-29
written: 2009-07-27
Contents
Introduction
Symbols
Aim
Research question
Independent variable
Dependent variable
Controlled variables
Hypothesis
List of material
Preparation
Method
Analysis
Conclusion 6
Evaluation
Introduction
A conductor induces a magnetic field around itself while carrying a current. This magnetic field has the same properties as normal magnetic field in all aspects except that the field is oriented in a closed circle around the conductor following the right hand rule.
Symbols
In this experiment following symbols are used:
B = magnetic field [T]
I = current [A]
V = voltage [V]
R = resistance [Ω]
r = radius [m]
µ0 = permeability of free space (constant) [4π*10-7 TmA-1]
Aim
The scientist is supposed to investigate the relationship between current and magnetic field in a conductor by running a varying current through a circuit and measure the magnetic field induced by it. Furthermore the practical skills in the subject of the magnetism and electrical currents should improve.
Research question
How is the magnetic field (B) dependant on the current (I)?
Independent variable: Current (I)
Dependent variable: Magnetic field (B)
Controlled variables:
- Radius (r)
- Permeability of free space (µ0)
Hypothesis
Middle
A value for the relationship between I and B can be found through processing the raw data found and creating a graph of it.
Processing the data into the universal formula for a linear graph (y=mx+c) B can represent the y value and I can represent the x value, making the m value represent m=µ0/2πr. (see next page for graph) solving this formula for µ0 makes:
µ0 = maverage2πr
µ0max = mmax slope2πr
µ0min = mmin slope2πr
Notice that the real value of m is only 1/1000 of the value presented in the graph as mT is used as unit in the data table. Furthermore r is kept constant at 1 cm.
Trial #1
Thus m = 2.14*10-5 TA-1, mmax slope = 2.39*10-5 TA-1 and mmin slope = 1.99*10-5 TA-1
µ0 = (2.14*10-5)*2π*0.01 = 4.28π*10-7 TmA-1
µ0max = (2.39*10-5)*2π*0.01 = 4.78π*10-7 TmA-1
µ0min = (1.99*10-5)*2π*0.01 = 3.98π*10-7 TmA-1
inaccuracy = (max-min)/2
(4.78π*10-7-3.98π*10-7)/2 = 4π*10-8 TmA-1
Thus the calculated value for µ0 is:
4.28π*10-7 TmA-1 ±4π*10-8 TmA-1
The V/I relationship also known as the resistance of the circuit is controlled by the table to the right. As is implied in this table the resistance remained ohmic as it should.
Trial #2
In Trial #2 the radius was kept constant at 1.
Conclusion
Both the fact that the graph is linear and that the calculated value supports the hypothesis as the real value lies within the inaccuracy. Also the fact that the repeated data collection is accurate supports known theory and the hypothesis.
Evaluation
The evaluation seems reasonable as the results were close to the real value all implying that the lab was well designed and executed. However the magnetometer was very sensitive to external factors and made several resets of the scale were necessary before a data collection could be performed. The inaccuracy of the readings of the magnetic field made the error bars in the graph unnecessarily large.
The fact that the y intercept is not zero in the first two graphs suggests a minor systematic error however the error remains unidentified. The repeated measurement and calculation of average removes the unavoidable difficulties in making accurate measurements every time.
There are not many ways this laboration can be improved, except for finding the systematic error, as it gave a clear and correct value.
Tingvallagymnasiet Physics Department
This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.
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