# Lab 3b Tips: Electromagnetic Forces

## Pre-lab

- Notice that
*g* is a function of voltage *v* and not of velocity *v*_{x}.
- This pre-lab is simpler than it might appear. The Simulink model provided in the pre-lab simulates the plunger-solenoid system by implementing a set of differential equations including the one you have been asked to derive. As such, if you are stuck you can try to determine the necessary equation for
*λ'* by looking at the model. For convenience a reorganized version of the model from the manual has been provided below.

## In-lab

- To find the simulated pull-in times, use the
*x*-axis zoom tool. Zoom in on the step change of the velocity plot. This step occurs exactly at the same time as the lowest point in the current dip (Why?). Use all available precision for the time data
- Add a manual switch to your model. Double clicking toggles the switch.

- See Single Trigger Mode
- See Paired Cursors
- Use snapshot in digscope to capture the measured pull in time and then print the result. Make sure your snapshot includes paired cursors measuring the pull-in times.

### Check your work.

- Don't forget to label your plots with position and mass settings.
- Make sure your simulated and measured values agree.

## Post-lab

- Divide the transient current waveform into three regions and analyze them each separately.