Use “Fun Fly Stick” to charge up conductive sheet.
Mylar strands align with electric field.
Place support rods together to form cylinder. Electric field of cylinder points outward radially.
- Located in L01, section A-2
field
Ferrofluid
Developed by NASA Scientist Steve Papell in the 1960’s, Ferrofluid is a colloidal liquid made of paramagnetic nano particles. When subjected to a magnetic field, the nanoparticles form regular patterns of peaks and valleys.
For an interesting list of modern applications see:https://en.wikipedia.org/wiki/Ferrofluid
- Located in L01, section B-2 (in bin with iron filings)
Jumping Ring
- Fluctuating B field causes ring to either 1) jump off of apparatus, or 2) levitate.
- For new apparatus (right in top picture): plug into wall and push the switch on the right down to let current flow. For old apparatus (left in top picture): plug Apparatus into variac; turn variac knob to set current amount; flip variac switch to “on” position to produce instantaneous B field.
- For added excitement, cool rings with LN2 to increase conductivity.
Notes about use
- For old apparatus: apparatus is pretty old. Iron rods not securely connected to wooden base. Hold onto base and rods, when lifting or transporting.
- Do not touch apparatus when current is flowing (variac on or switch pressed).
- Jumping ring apparatus located in L01, section B2. Variac
located in L01, section A1.
Parallel Currents
- Demonstrate force between parallel currents.
- Using two power supplies, send current through both stationary and balancing wires.
- Angle of mirror connected to pivot will change as wires are pulled together or pushed apart due to Lorentz force. A laser beam, deflected by mirror, can be used to show the otherwise imperceptible change of mirror angle.
- To determine the strength of the Lorentz force: mark the laser position on a distant wall both with and without current- using current that produces attraction, not repulsion. Then, with current off, place small pieces of folded up tin foil on top of movable wire (using platform on wire) until deflection of laser matches that produced by Lorentz force. Weigh tin foil pieces with sensitive digital scale to determine gravitational force.
- Compare gravitational force to Lorentz force.
- Distance between wires, and wire length, can be measured using ruler. Current can be measured using Ammeter.
- Current balance located in L01, section B3.
- Power supply, laser, digital scale, ammeter, and tin foil in L35.
Magnetic Torque
- Demonstrate torque experienced by magnetic dipole in B-field.
- Measure magnetic moment of dipole.
- Show that net force experienced by magnetic dipole
is zero in uniform B-field, and non-zero in B-field with gradient. - See instructors manual for experimental details.
- Located in L01, section B2.
Field around Current
- Place tiny compasses around current carrying wire to see
circular magnetic field. - Located in L01, section B2. Power supply in section A1; cables
on wall.
B-field Demonstrators
- Located in L01, section B2
Current Balance
- Purpose: Demonstrate how the magnetic force on a current
carrying wire depends on the angle between the current and the external B-field.
Location
- Current Balance in L01, sectionB3
- Power supply in L35, section F1
- Multimeter in L35, section F3.
Gauss’s Law
- Show that flux (# of sticks that poke inner lining of plastic
bag) is independent of shape of enclosure. - Located in L02, section D1.
Faraday Cage
- Use the cage in conjunction with Van de Graaff to demonstrate
electrostatic shielding. - Place a hand-held radio inside the cage to demonstrate electromagnetic
shielding (radio in cage should pick-up no signal). - Located in L01, section A2.
Van de Graaff Gen.
- Principle: Static electricity is cool.
- Located in L01, section A2
- Van de Graaf accessories are located beneath Van de Graaff
generator in plastic containers.
Some ideas for experiments beyond the typical shock-myself-and-my-students:
- Bend a paper clip into an L shape and tape it to the charged sphere to create
an ion gun; point the paper clip at the palm of your hand to feel the “ion
wind”. Point the paper clip at your shirt to charge your shirt up- after
30 seconds shirt should begin sticking to your chest. - Place a cup of styrofoam peanuts, or a stack of styro or aluminum plates
on top of the sphere, turn on generator and watch stuff fly. - Dim the room lights, touch one end of a fluorescent bulb to the charged
sphere and the other end of the bulb to the small discharging sphere. Bulb
will flicker. - Using a squirt gun shoot a stream of water past the charged sphere; water
should ionize and stream will disperse.