Magnetic Force on Current Carrying Wires

1
Magnetic Force on Current Carrying Wires

• Curtis H. Choi
• Joseph Wassei
• Jonathan Po
• Physics 2B Laboratory Presentation
• Costantino
• Las Postias College
• April 25,2003.

2
Background

• History of Magnetism
• Magnesia
• Lodestones attract pieces of iron
• Chinese
• Compasses made of lodestones
• William Gilbert (1500s)
• Artificial magnets, by rubbing lodestone and iron
• electrics attracting various materials (Amber
  (G))
• Static electrical attraction to a magnetic
  attraction
• Electrical attraction may be transmitted through
  an object

3
Background

• History of Magnetism cont.
• Hans Christian Ørsted (Physicist)
• Accidental discovery re-linking electric and
  magnetic theory
• Ampére (Mathematician)
• Source of magnetic field is electric current, as
  the source of an electric field is an electric
  charge
• Magnetic field (B) around a wire is proportional
  to the current flowing through the wire
• Right hand rule
• Two current-carrying wires attract/repel
  depending on direction of current

4
Theory

• Interaction between a moving charge and a
  magnetic field can be described as followed
• FqvBsin? (Eqn. 1)
• q magnitude of moving charge, v velocity B
  magnetic field
• Extended using cross-sectional area A and Length
  L carrying current I
• F qvdB (Eqn. 2)
• vddrift velocity

5
Theory

• Since VAL the number of carriersnAL the
  magnitude of total magnetic force on a wire with
  length L is
• F(qvdB)(nAl) (Eqn. 3)
• Since InqvdA, F may be expressed
• F ILBsin? ILB (Eqn. 4 5)
• Assumptions made in our experiment none of the
  electrons escape into the atmosphere, also
  neglect all forces on magnetic holder other than
  gravitation and electrical (magnetic)

6
Experimental Arrangement

• Obtain the following equipment
• Basic Current Balance and Accessory
• Quadruple-Beam Gram Balance
• DIGI Power Supply
• DMM
• Patch cords

7
Experimental Arrangement
Assemble apparatus (used in Part A C)
8
Experimental Arrangement

• Part A
• Assemble apparatus
• Determine and record the mass of the magnet
  holder and magnets with no current flowing (m0).
  

Magnet holder
Magnets
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Experimental Arrangement

• Part A
• Assemble apparatus
• Determine and record the mass of the magnet
  holder and magnets with no current flowing (m0).
  
• Measure the new mass of the magnet assembly in
  different current settings (0.5amp 2.0amp
  increasing the current in 0.25 increments).

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Experimental Arrangement Part B

• Part B
• Determine and record the length of the
  conductive foil on the current loop (L).
• Determine the new mass of the magnet assembly
  at 2.0amps current and record it as m(L).
• Subtract m0 from m(L) and record as F(L).
• Repeat the above steps with all the other current
  loops.

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Experimental Arrangement

• Part C
• Mount a single magnet in the center of the
  holder.
• Determine the mass of the magnet assembly
  without current flowing and record as m(n).
• Set the current to 2.0 amps. Determine the new
  mass of the magnet assembly and record it as
  m(n,c).
• Subtract m(n) from m(n,c) and record the
  difference as F(n).

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Experimental Results

• This apparatus was used in Part A Force vs.
  current, Part B, Force vs. length of wire, and
  Part C Force vs. magnetic field.
• Magnetic holder weight(m0) .1614 Kg

Quadruple-beam balance
Current loop
Main unit
Magnetic holder
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Part A Force vs. Current

• The equation of the graph is Y .0002x - 2E-6.
• The slope of the line was found to be .0002 LT.
• The slope of the line is LB from the equation
  (F/I)LB.
• This equation tells us that if the current
  increases so does the force acting on the wire.

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Part A Force vs. Current

• The equation of the graph is F sI F0
• The slope of the line is s BL 2.xx(10-4)
  N/A
• For L 2.00 cm, B 0.076 T

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Part B Force vs. Length of Wire

• The equation of the graph is Y.0432x - .0004.
• The slope is .0432 A T.
• The current was 2.0 Amps
• The slope of the line is IB from the equation
  (F/L)IB.
• As length of wire increases so does force acting
  on the wire.
• Equation
• slopeBI
• B .0432/2 .0216 T

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Part C Force vs. Magnetic Field

• The equation of the graph is y 7E-7x 4E-5.
• The slope of the graph is 7E-7 N per magnet.
• As the number of magnets inc. so does the Force
  in the magnetic field.

17
Errors

• Possible errors in this experiment are
• The quadruple-beam balance was not calibrated
  correctly.
• Length of the conductive wire measured might have
  been measured incorrectly.

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Conclusion

• The magnetic field was found to be .0216 T using
  the equation slope BI
• It was found that as the current, number of
  magnets, and the length of the conductive foil
  inc so does the force in the magnetic field.

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Magnetic Force on Current Carrying Wires

• Curtis H. Choi
• Joseph Wassei
• Jonathan Po
• Physics 2B Laboratory Presentation
• Costantino
• Las Postias College
• April 25,2003.