# Magneto-hydrodynamic Drives

By T2T Contributor, David Richards

Objective:
The objective of this lesson and demonstration is to get the students to see how electric and magnetic fields can be used to force water out of a chamber in order to propel a vehicle such as a submarine.

Resources:
Small tray 12in x 5in x 2in
two conducting bars (i.e. aluminum)
a DC power supply (capable of 2A)
a strong horseshoe magnet
water
salt
pepper

Teacher Preparation:
Need to understand the basic principles behind crossed eclectric and magnetic fields

Procedure:
Take the two conducting bars and place them in the tray. Hook the leads from the power supply to the conducting bars. Pour water into the tray until it is about 1 inch deep. Place horseshoe magnet so that the poles are between the two conducting rods (above and below the tray). Poor salt into tray and stir. Next, poor some pepper in. Now turn on the power supply and crank up the voltage until you get a current to flow between the two conducting rods You will see the pepper begin to circulate around the conducting rods.

Variations/Options:
This principle is used in submarines like the one in “The Hunt for Red October”. It is a propulsion drive that has no moving mechanical parts, therefore it is difficult to detect through sonar. The students can come up with other examples of this phenomenon.

Real World Usage:
Students should think about how this phenomenon can be modified for different uses.