Figure 1
Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic field. Michael Faraday was the first to describe this phenomenon mathematically. He found that the electromotive force (EMF) produced along a closed path is proportional to the rate of change of the magnetic flux through any surface bounded by that path. In practice, this means that an electrical current will flow in any closed conductor, when the magnetic flux through a surface is bounded by the conductor changes. This applies whether the field itself changes in strength or the conductor is moved through it. The mathematical expression of Faraday’s Law is given by: đ?œ€=
∆đ?›ˇ ∆đ?‘Ą
Where: =ď€ ď€ The electromotive force (EMF) produced along a closed path ÎŚ = The magnetic flux through any surface bounded by that path In this experiment we will investigate this relationship Ć?
(1)
einstein™Tablet+ with MiLAB or Android/iOS Tablet with MiLAB and einstein™LabMate Voltage sensor (2.5 V) Magnetic Field sensor Two coils with the same physical dimensions. One with about 500 turns (the low turn coil) and the other with about 10,000 turns (the high turn coil) Signal generator with power output Connecting wires
1.
Launch MiLAB (
2. 3. 4.
Connect the Magnetic Field sensor to one of the ports on the einstein™Tablet+ or einstein™LabMate. Connect the Voltage sensor to one of the ports on the einstein™Tablet+ or einstein™LabMate. Assemble the equipment as shown in Figure 1. a. Place the coils on the table facing each other. b. Connect the low turn coil (primary coil) to the power supply. c. Connect the high turn coil (secondary coil) to the Voltage sensor. d. Insert the Magnetic Field sensor into the low turn coil. Set the sensor switch to the high sensitivity range. Use the pull down menu in the Sensor Control Panel to select the Magnetic Field sensor. Make sure that only the Magnetic Field and Voltage sensors are selected.
5. 6. 7.
).
Program the sensors to log data according to the following setup: Magnetic Field Sensor
Magnetic 0.2 mT (mT)
Voltage Sensor (2.5 V)
Voltage (V)
Set As Zero
ON
Rate:
100/sec
Duration:
10 Sec
1. Turn on the signal generator. 2. Adjust the signal generator to a frequency of 1 Hz and triangular waveform. 3. Tap Run (
) to begin recording data.
4. Wait for 20 seconds then tap Stop ( 5. Save your data by tapping Save (
). ).
6. Change the signal generator’s frequency to 2 Hz and repeat steps 3 to 5. 7. Return to a frequency of 1Hz and change the signal generator’s waveform to sinusoidal, then repeat steps 3 to 6.
For more information on working with graphs see: Working with Graphs in MiLAB. 1.
Select Archive (
) and then select and display the first graph you produced.
2.
Discuss the graph in view of Faraday’s Induction Law (Equation (1)).
3.
Select Archive (
4.
Discuss the graph in view of Faraday’s Induction Law. What was the effect of doubling the frequency?
5.
Select Archive (
) and then select and display the second graph you produced. ) and then select and display the third graph you produced.
Discuss the graph in view of Faraday’s Induction Law. Does the induced voltage graph fit the derivative of the magnetic field function?