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# Magnetism labs

### Station 1 electromagnet

We don’t see magnetic fields directly – but we can see their effect. By putting a tiny piece of metal near our electromagnet, we can see if/how it is moved. If we trace out the motion of many test particles, we would generate a pattern that would look something like this:

### Station 2 St. Louis Motor/Induction Motor

Look at the animations here to see how motors work. http://www.animations.physics.unsw.edu.au/jw/electricmotors.html

Also see the explanation at Hyperphysics DC Motors

External resources

http://www.csun.edu/scied/1-demo/induction_motor/

### Station 4 – Ring launcher – Elihu Thomson apparatus

Demonstrates Lenz’s law and effects of electromagnetically induced currents.

When the switch is flipped, the suddenly-increasing magnetic field induces current to flow in the ring. The current creates an magnetic field opposing the original field. The field from the post and the field from the induced current in the ring repel each other just as north poles of two bar magnets would. It is this strong repulsion that launches the ring into the air.

If the first aluminum ring is replaced by another one that has a split completely down one side, then can a steady current be induced in the ring? No, because the ring doesn’t form a complete circuit. That means that when this ring is placed on the launcher and the magnetic field through it is increased, no current can be induced in the ring. Therefore, the ring can’t produce its own magnetic field. No induced magnetic field … no repulsion, and the ring never leaves the launcher.

http://demos.smu.ca/index.php/demos/e-n-m/51-rail-gun

more resources:

Elihu Thomson – One of the greats like Thomas Edison and Nikola Tesla

### Station 5 – neodymium homopolar motor

https://en.wikipedia.org/wiki/Homopolar_motor

### Station 6 -Faraday’s law of induction

Coils of wire, magnets, an ammeter, and banana-to-alligator wires.

### Station 7 – Lenz’s law demo

Good step by step explanation here: http://regentsprep.org/regents/physics/phys08/clenslaw/

### 2016 Massachusetts Science and Technology/Engineering Curriculum standards

7.MS-PS2-5. Use scientific evidence to argue that fields exist between objects with mass, between magnetic objects, and between electrically charged objects that exert force on each other even though the objects are not in contact.

7.MS-PS3-2. Develop a model to describe the relationship between the relative positions of objects interacting at a distance and their relative potential energy in the system. {Examples could include changing the direction/orientation of a magnet.}

HS-PS2-5. Provide evidence that an electric current can produce a magnetic field and that a changing magnetic field can produce an electric current.

HS-PS3-1. Use algebraic expressions and the principle of energy conservation to calculate the change in energy of one component of a system when the change in energy of the other component(s) of the system, as well as the total energy of the system including any energy entering or leaving the system, is known. Identify any transformations from one form of energy to another, including thermal, kinetic, gravitational, magnetic, or electrical energy, in the system:

Chemical potential energy is stored in our muscles as ATP; this is transformed into translational kinetic energy (KE) as we move our hand; this gives the magnet it’s own KE.  The magnet’s moving magnetic field then creates electrical energy in the coil, which we measure with an ammeter, thus addressing HS-PS3-3.

HS-PS3-3. Design and evaluate a device that works within given constraints to convert one form of energy into another form of energy.

HS-PS3-5. Develop and use a model of magnetic or electric fields to illustrate the forces and changes in energy between two magnetically or electrically charged objects changing relative position in a magnetic or electric field, respectively.