Download Magnetic “Hydrojet”

Magnetic “Hydrojet”
SCIENTIFIC
Movie Magic or Movie Science
SCIENCE FAX!
Introduction
In the Tom Clancy novel, The Hunt for Red October (1984), and movie of the same title (1990), a submarine was designed
with a unique, silent-running propulsion system. The novel refers to this system as a hydrojet, whereas the movie calls it
a magnetohydrodynamic drive, or “caterpillar” drive. Show your students the principles behind this propulsion system and
discuss whether it would be powerful enough to push a submarine.
Concepts
•Electric force
•Electrolysis
• Magnetic force
• Newton’s second and third laws of motion
Background
The principle behind the revolutionary propulsion system used in The Hunt for Red October is based on the relationship
between magnetic fields, electric fields and moving charged particles. A charged particle traveling in a magnetic field will
be deflected by the magnetic field in a direction perpendicular to the particle’s initial motion (see Figure 1). The direction
of the force that causes the deflection is determined by the “right hand rule.” Point your index finger of your right hand in
the direction of motion of the particle, and face the palm in the direction of the magnetic field. Your thumb will point in
the direction of the force produced by the magnetic field. The force on negative charges is in the opposite direction to the
way the thumb points.
+
q
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X = Magnetic field (B)
pointing into the page
Figure 1.
The amount of force on the moving charged particle depends on the particle’s speed and the strength of the magnetic field,
according to Equation 1.
FM = qvB
Equation 1*
FM = force due to the magnetic field
q = charge on the particle
v = velocity of the charged particle
B = strength of the magnetic field
*Note that FM , v, and B are all vector quantities and the direction of FM is based on the “cross-product” of v and B, i.e., the “right hand rule.”
An electric field also produces a force on a charged particle according to Equation 2. The force produced by the electric
field is in the same direction as the electric field.
FE = qE
Equation 2
FE = force due to the electric field
E = strength of the electric field
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© 2017 Flinn Scientific, Inc. All Rights Reserved.
© 2016 Flinn Scientific, Inc. All Rights Reserved.
Publication No. 10842
061616
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Magnetic “Hydrojet” continued
The basic principles behind the “magnetohydrodynamic drive” are electrolysis and electrodynamics. A giant electrolysis
apparatus uses seawater (tap water) as the electrolytic solution to generate an electric field and to produce ions (charged
particles). Strong magnets are used to deflect the moving charged particles out the back of the submarine, which generates
thrust according to Newton’s third law of motion (action–reaction). See Figure 2 for a depiction of the forces and the motion
of the charged particles. The magnitude and the direction of the force due to the electric field are constant, while the
magnitude of the magnetic force is constant but its direction depends on the direction the particle is traveling (according to
the “right-hand rule”). Once the charged particles are deflected due to the magnetic field, the particles remain on a path
perpendicular to the electric field because the forces due to the electric field and magnetic field are now balanced. The
charged particles must continue to move in order for the forces to remain balanced. If the charged particles stop moving
(v = 0), then the magnetic field will no longer act on the charged particles.
Key
+
Electric field direction
X
FM
FE
X
+
X
q
Anode
+
(H produced)
X
X
+
X
X
X
X
–
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
–
q
Cathode
–
(OH produced)
X
X
X = Magnetic field (B)
pointing into the page
–
Figure 2.
This propulsion system created by the behavior of ions in an electric and magnetic field has advantages and disadvantages.
Electrolysis generates oxygen and hydrogen gases which could be used to sustain life support and to run fuel cells, respectively.
This unique submarine design also does not require the need to carry fuel for propulsion because it would use the surrounding
water. However, the design would still require a nuclear reactor to generate enough electricity to produce the strong electric
fields and electromagnets needed to create and deflect the ions (and water), respectively. As far as the submarine being “silent
running” as the novel and movie claim, that would depend greatly on the power systems used to generate the high voltage and
electromagnets. These systems would probably generate a great deal of “humming,” and if the oxygen and hydrogen gas
bubbles are not collected, the resulting bubbles would create a noisy environment.
Materials
Neodymium magnets, 3
Tape, transparent
Electrophoresis chamber with power cords
Video Flex® camera (optional)
Electrophoresis power supply (at least 75-V)
Water, tap
Food coloring
Safety Precautions
Electrical Hazard: Treat these units like any other electrical source—very carefully! Be sure to read and follow all electrical hazards
associated with the electrophoresis apparatus and power supply used in this demonstration. Be sure all connecting wires, terminals and work
surfaces are dry before using the electrophoresis units. Match the lead colors: red (anode) to red and black (cathode) to black. To view the
moving dye, the lid of the electrophoresis chamber must remain off. Connect the power supply directly to the electrodes of the chamber. Do not
touch the liquid or any of the cord connections when the power supply is turned on. Wear safety glasses. Handle the food dye carefully. It will
stain skin and clothing. Wash hands thoroughly with soap and water before leaving the laboratory.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Magnetic “Hydrojet” continued
Procedure
1. Obtain an electrophoresis chamber, tape and three neodymium magnets.
2. Tape the neodymium magnets to the outside bottom of the electrophoresis chamber along the centerline, perpendicular to
the direction the ions will travel (see Figure 3). Make sure the polarity of the magnets point in the same direction (i.e., the
“north” poles of the magnets all point down).
Electrophoresis chamber
Electrode
Electrode
Neodymium magnet taped
to the outside bottom of
chamber, north pole
pointing into the paper
Electrophoresis chamber
half-filled with water
Electrode
Add a drop of food dye here
Top view
Electrode
(Not to scale)
Magnets on the outside
Side view
Figure 3.
3. Fill the electrophoresis chamber about halfway with tap water (do not used distilled or deionized water).
4. Add a drop of food coloring near one of the magnets.
5. Connect the electrophoresis chamber directly to the electrophoresis power supply (do not place the lid on the
electrophoresus chamber).
6.(Optional) Set up a Video Flex camera to conveniently display the demonstration on a TV or computer screen.
7. Turn on the power supply and have students observe the motion of the dye and record their observations in the worksheet.
8. Repeat the demonstration by adding more dye, a different color dye, reversing the polarity of the electric field (reversing
the connecting leads) or by disconnecting the chamber from the power supply, emptying the chamber and filling with fresh
tap water. Discuss the observations with students.
Disposal
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures governing
the disposal of laboratory wastes. The resulting food dye solution may be disposed of down the drain with excess water
according to Flinn Suggested Disposal Method #26b.
Connecting to the National Standards
This laboratory activity relates to the following National Science Education Standards (1996):
Unifying Concepts and Processes: Grades K–12
Systems, order, and organization
Evidence, models, and explanation
Content Standards: Grades 5–8
Content Standard B: Physical Science, understanding of motions and forces, transfer of energy
Content Standard E: Science and Technology
Content Standards: Grades 9–12
Content Standard B: Physical Science, motions and forces, conservation of energy and increase in disorder,
interactions of energy and matter
Content Standard E: Science and Technology
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Magnetic “Hydrojet” continued
Tips
• Any electrophoresis chamber will work for this demonstration, but it best to use one that has legs so that the magnets will fit under the chamber and the chamber will remain stable. If a flat-bottomed electrophoresis chamber (i.e., no legs) is used, place the two short edges of the chamber onto books of equal height to create a “bridge” that will allow the
magnets to fit below the chamber.
• Neodymium magnets and Mega-Magnets are strong and create very visible currents. Any strong magnets will work, however. Handle these magnets carefully. They can quickly snap together and pinch skin. They are also fragile and may shatter, crack or chip if dropped on the ground. They are difficult to pull apart. It is often better to slide them apart.
• (Optional) Perform a “control” experiment without the magnets attached to the bottom before creating the “hydrojet.” The dye will travel toward the electrodes of the electrophoresis chamber.
• Change the orientation of the magnets to see how the ion currents are affected. Standing the cylindrical neodymium magnet on its edge generates a swirling ion current that appears to produce ion “containment.” For advanced classes,
discuss fusion reactor designs and the possibilities of plasma containment.
• Keep neodymium magnets away from computer disks or other magnetic strips such as credit cards. They will quickly erase the magnetized data.
Answers to Worksheet (Student answers will vary.)
Observations
Sketch a diagram of the initial setup, including the location of the drop of food dye.
Sketch a diagram of the final result, including the direction of the motion of the dye, and explain what occurred.
Direction
of dye
movement
Initial
The dye traveled
“up” parallel to the
line of magnets,
until it hit the wall
of the chamber
and dispersed in
circular patterns.
Final
Post-Demonstration Questions
1. Which of Newton’s three laws of motion provides the basis for a rocket propulsion-type engine. Define the law(s) chosen.
A rocket propulsion-type engine relies on Newton’s third law of motion, or for every action there is an equal and opposite reaction. It also
relies on Newton’s second law of motion—a force causes a mass to accelerate.
2. Do you believe this magnetohydrodynamic system could be used to push a submarine? Why or why not?
Student answers will vary. Most will agree that this type of system could be used as a propulsion system for a submarine, if it could
generate enough power.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Magnetic “Hydrojet” continued
Materials for Magnetic “Hydrojet” are available from Flinn Scientific, Inc.
Catalog No.
AP1738
AP5666
FB0315
FB0327
FB0830
FB1121
V0003
Description
Mega-Magnet
Neodymium Magnet
Electrophoresis Power Pack
Electrophoresis Apparatus, Economy
Flinn Economy Electrophoresis Kit
Video Flex® Model 2100
Food Coloring Dye Set
Consult your Flinn Scientific Catalog/Reference Manual for current prices.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Magnetic “Hydrojet” continued
Magnetic “Hydrojet” Worksheet
Observations
Sketch a picture of the initial setup, including the location of the drop of food dye.
Sketch a picture of the final result, including the direction of the motion of the dye, and explain what occurred.
Post-Demonstration Questions
1. Which of Newton’s three laws of motion provides the basis for a rocket propulsion-type engine. Define the law(s) chosen.
2. Do you believe this magnetohydrodynamic system could be used to push a submarine? Why or why not?
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© 2016 Flinn Scientific, Inc. All Rights Reserved.