Magnetic Fields

Forces on Moving Charges in Magnetic Fields

Video RealVideo®
5:12 minutes (18:34 - 23:46)

Showing the circular motion of electrons in the magnetic field of a Helmholtz coil using a gas-filled glass tube.

Instructor: Prof. Walter Lewin
Prior Knowledge: Moving Charges in Uniform Fields (1:21 of VL13)
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Video RealVideo®
3:30 minutes (21:25 - 24:55)

Explanation of how electrons are used to make an image on a TV screen, with a demonstration showing that a magnet will distort this picture when placed near the screen.

Instructor: Prof. Walter Lewin
Prior Knowledge: Strength of Magnetic Fields (17:20 of VL11)
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Video RealVideo®
2:28 minutes (12:29 - 14:57)

Using an electron gun and a magnet to show that the path of an electron will curve in the presence of a magnetic field.

Instructor: Prof. Walter Lewin
Prior Knowledge: Moving Charge in Uniform Magnetic Field (1:21 of VL13)
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Video RealVideo®
4:25 minutes (44:32 - 48:57)

Tracking the motion of electrons and alpha particles in a cloud chamber.

Instructor: Prof. Walter Lewin
Prior Knowledge: Cloud Chambers (34:42 of VL13)
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Forces on Current-Carrying Wires in Magnetic Fields

Video RealVideo®
3:27 minutes (9:26 - 12:53)

Finding the force a magnetic field exerts on a current-carrying wire, with a demonstration of a wire jumping in a strong magnetic field.

Instructor: Prof. Walter Lewin
Prior Knowledge: None
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Video RealVideo®
3:06 minutes (46:42 - 49:48)

Creating a motor from a current loop where the current is manually reversed after every 180° of rotation.

Instructor: Prof. Walter Lewin
Prior Knowledge: Motor Contest - Force and Torque on Current Loop (34:39 of VL11)
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Fields of Long Current-Carrying Wires

Video RealVideo®
4:42 minutes (4:44 - 9:26)

Finding the direction of the magnetic field created by a current-carrying wire, with introduction to the right hand rule and a demo of a compass needle responding to the current through a wire.

Instructor: Prof. Walter Lewin
Prior Knowledge: None
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Video RealVideo®
4:27 minutes (12:53 - 17:20)

Forces felt by two parallel current carrying wires, when the currents are in the same or in opposite directions. Includes a demonstration of these forces.

Instructor: Prof. Walter Lewin
Prior Knowledge: Field of Current-Carrying Wire (4:44 of VL11)
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Biot-Savart's Law and Ampere's Law

Video RealVideo®
7:19 minutes (20:05 - 27:24)

Using iron filings to view the magnetic field of a loosely wrapped solenoid, and using a Hall probe to measure the magnetic field inside and around a tightly wrapped solenoid.

Instructor: Prof. Walter Lewin
Prior Knowledge: Ampere's Law for Solenoids (12:44 of VL15)
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