Electricity and Magnetism

5K 10.15 - Induced EMF

Demonstrates: Motional EMF, Faraday's Law
Description: When a long wire is moved between the poles of a large permanent magnet, an emf is generated. The resulting current in the wire is detected with the galvanometer.

5K 10.20 - Induction Coil with Magnet & Galvanometer

Demonstrates: Faraday's Law
Description: Various coils of wire are attached to a galvanometer that registers a current (EMF)when a bar magnet is passed through them or when the coils pass through a large horseshoe magnet.

5K 10.40 - Open Transformer

Demonstrates: Faraday's Law.
Description: Primary Coil is connected to A/C power supply. Secondary coil is connected to light bulb. Magnetic field of the primary induces current in the secondary. Lift the secondary coil off the primary and the bulb goes out. The iron core can be inserted to amplify the effect.

5K 20.10 - Eddy Currents in Pendulum

Demonstrates: Eddy Currents, Faraday's Law, Lenz's Law
Description: When the solid aluminum paddle swings past the electromagnet, eddy currents are induced. The magnetic forces on these currents oppose the motion and the the pendulum stops. Very dramatic if the pendulum is released from a large height! When the paddle with closed slots is used, the path length and therefore resistance for the induced currents increases, producing a smaller damping. With the open slotted paddle, almost no damping occurs.

5K 20.25 - Magnets in Eddy Tubes

Demonstrates: Lenz's Law, Faraday's Law
Description: When a non-magnet is dropped down a copper tube, it falls freely. When a strong magnet is dropped down the same tube, currents are induced in the tube. The magnetic field of the induced currents oppose the field of the magnet, slowing it down. The magnet takes several seconds to drop through the tube. Viewed from the top, the magnet seems to float down.

5K 20.30 - Jumping Rings

Demonstrates: Lenz's Law, Faraday's Law, Magnetic Levitation
Description: A ring is placed atop the solenoid which has an iron core. When AC power is supplied to the solenoid, the changing magnetic flux induces a current in the metal ring. The induced magnetic field of the ring is opposite the field of the solenoid and the ring is repelled off into the air. A split ring does not allow current to flow, and does not fly off.

5K 30.10 - Transformer

Demonstrates: Voltage conversion and inductance.
Description: Voltage can be stepped up or down. As voltage is increased current is decreased.

5K 40.40 - DC Motor

Demonstrates: Direct current.
Description: When power is supplied to the electromagnet a DC motor is put into motion.

5K 40.45 - AC Generator

Demonstrates: Alternating current.
Description: Meter needle shows that current is alternating.

5K 40.80 - Hand Crank Generator

Demonstrates: Generators.
Description: Turn the crank on the generator to light the bulb.