Download 213Lab10-FaradaysLaw

Phy 213 General Physics III
Instructor: Tony Zable
1
Experiment: Faraday’s Law & Electromagnetic Induction
Objective: To investigate the properties of electromagnetic induction.
Equipment:
 LoggerPro software
 LabPro Interface
 Voltage Probe
 Magnetic Field Sensor
 Analog Out Connector
 Large spring
 solenoid
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ring stand and clamps
connection wires
analog galvanometer
4-5 neodymium magnets
5V DC power supply (or battery)
masking tape
medium size binder clip
Introduction:
A magnetic field can exert force on a moving charge. Alternatively, a moving (or
changing) magnetic field can exert force on a stationary charge.
Part 1: Electromagnetic induction
1. Set-up the simple solenoid circuit
shown below:
magnet
galvanometer
2. Move a pair of block magnets
(pole facing solenoid) back and forth
along the axis of the solenoid
opening. What do you observe?
solenoid
3. How does the motion of the magnet affect the current observed by the meter?
File name: 493730495
Phy 213 General Physics III
Instructor: Tony Zable
2
Part 2: Faraday’s Law
1.
Connect Voltage Probe to Ch1 of LabPro interface then connect the Analog Out
connector to Ch4.
2.
Start LoggerPro software and set the data collection interval to 5s and the rate to
maximum setting (~1000 samples/s).
3.
Set-up the simple solenoid circuit shown below:
a. Attach Magnetic Field Sensor to bottom of ring stand with white dot pointed
upward
b. Position solenoid above the magnetic field sensor (about 9 cm above table top)
c. Attach a spring to a support rod and attach the stacked block magnets to the
spring, using a binder clip and tape.
d. Position the spring so that
the magnets suspend about
halfway down into the
solenoid (the only concern is
that the magnetic field sensor
signal does not saturate and
that the magnets do not rub
against the sides of the
solenoid or bump the field
sensor below).
e. Connect voltage probe leads
to the solenoid.
4.
Contract the spring then release
it so that the magnets oscillate
up and down. The motion
should a small displacement so
that the motion is roughly
sinusoidal.
Binder
Clip
Block
magnets
Solenoid
Voltage
Probe
Magnetic Field Sensor
5.
Collect Potential vs time and Magnetic Field vs time measurements using
LoggerPro. Verify that observed magnetic field and potential are roughly sinusoidal.
If the signals are not sinusoidal in shape, adjust your apparatus and re-collect.
6.
Cut-and-paste the Potential and Magnetic Field Graphs into Word.
7.
Create a Continuous Function (Curve Fit) for the Magnetic Field Data. When
you are satisfies with your data collection, you will need to fit your B vs t graph to a
continuous function (Bfit) so that the time derivative (dBfit/dt) can be calculated. Fit
the sinusoidal region of the magnetic field data to a “Sine” function. In the Curve
Fit Window, click on Create Calculated Column then Show Curve Fit. Click Okay.
Re-label the new data column to “Bfit” and enter the appropriate units.
8.
Create a calculated column to calculate dBfit/dt. You will need to enter the
appropriate mathematical definition into the Equation field. Create a plot of V vs
dBfit/dt. Unfortunately, you will not yet be able to perform a Curve Fit for this
graph.
9.
Sort the Data Values using Excel. The LoggerPro data will need to be sorted so
File name: 493730495
Phy 213 General Physics III
Instructor: Tony Zable
3
that a curve fit for the V vs dBfit/dt graph can be performed. Use CTRL-A to
highlight all of the values in the Data Window then cut-and-paste the data into an
Excel spreadsheet. With the values still highlighted, sort the data by Potential
values (probably column 3, but verify this).
10. Cut-and-Paste the Sorted Data into Graphical Analysis. Export the sorted data
into Graphical Analysis and Label the columns appropriately. Create a graph of V
vs. dBfit/dt. Fit the graph to an appropriate function and record the fit parameters
with uncertainties.
11. Cut-and-paste the graph into Word. Print all of the graphs.
Fit Function:
(i.e. y=mx + B)
Coefficient Label
Value (w/ units)
Uncertainty
Questions:
1. Using your V vs. t and B vs. t graphs as reference, how does the changing magnetic
field affect the induced voltage in the solenoid?
2. Can you explain why the V vs. t graph looks so choppy and granular?
3. What is the significance of the slope of the V vs. dBfit/dt graph?
4. Explain how increasing or decreasing the number of suspended magnets would affect
the induced voltage in the solenoid? Consider both the mass of the magnets and
magnetic fields in your response.
5. Construct an equation based on your data for the relationship between V & B (this is
your interpretation of Faraday’s Law).
File name: 493730495