Lenz’s Law: A Magnet through a coil

Introduction

In 1834 a scientist call Emil Lenz,  deduced that the direction of the induced EMF is such that it tends to oppose the motion or change that caused it.  Hence Lenz’s law. Today with the evolution of sensors it’s now possible to measure the induced eddy currents. In this experiment, we are going to use a Go Direct Voltage sensor to measure the induced voltage as the magnet travels through a coil.

Objectives

In this experiment, you will

• Use a Voltage sensor to measure the induced voltage when a magnet goes through a wire coil

Equipment needed

Go Direct® Voltage Sensor (or Voltage probe)
Laptop/ PC/ Chromebook/ Tablet/ Smart phone
Clear plastic tube
Magnet that fits inside the plastic tube
Winding wire

Method

Prepare the coil tube
a. Make sure the magnet will freely travel down the inside of the tube.
b. Measure half way down the tube and mark it
c. Wind x turns around the tube at the marked point
d. Connect the voltage sensor to the coil.

Sensor Setup

On the Go Direct® Voltage Sensor, press the power button once. The LED will blink red. Launch the Graphical Analysis App. Click Sensor Data Collection.  Now select GDX-VOLT from the list (if you have more than one device, select the serial number corresponding to that on the case). The LED on the connected sensor(s) will now blink Green.  Change the sensor channel range to 1V. Click DONE. 

Measuring the Induced voltage

1. Click mode:time Based (bottom left)
2. Change the duration to 1000 sample/s
3. Change Start Collection to “on a triggering event”
4. Change the across voltage to 0.01V (depending on your magnet this might need to be larger or smaller)
5. Enter 500 to the box After Collect  500 points before trigger
6. Set End Duration  After 1 Seconds
7. Click Done

1. Press Collect
2.  The Screen will display Collecting 500 points, wait
3. Then the screen will display waiting for Potential 1 to increase across 0.01V
4. Drop the magnet
5. The Data Collection will stop automatically after 1 second.

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