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### Magnetic Field

• A compass needle may be used to map the magnetic field lines.
• An electric field exerts a force on a charge, whether the charge is stationary or moving. A magnetic field, however, exerts a force on a charge only if it is moving. The force is given by F = q v x B; it is the charge q times the cross product of the velocity v and magnetic field vectors.
• Since the magnetic force is always perpendicular to the velocity, a magnetic does no work on a moving charge, and thus it does not change its speed.
• If a charge, in a region where a uniform magnetic field exists, is given an initial velocity perpendicular to the field, then it will move in a circle.

### Magnetic Field

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

• Intro 0:00
• Magnets 0:13
• Compass Will Always Point North
• Moving a Compass Needle
• Force on a Charged Particles 10:37
• Electric Field and Charge Particle Q
• Charge is Positive Force
• Charge Particle is At Rest
• Taking a Charged Particle and Moving to Right
• Using Right Hand Rule
• C= Magnitude of A, B
• Magnitude of C
• Motion of Particle in Uniform Magnetic Field 33:30
• Magnetic Field has Same Direction
• Direction of Force
• Work Done By Force=0
• Force is Perpendicular With Velocity
• Bending an Electron Beam 48:09
• Heating a Filament
• Kinetic Energy of Battery
• Introducing Magnetic Field
• Velocity Selector 53:45
• Selecting Particles of Specific Velocity
• Parallel Plate Capacitor
• Magnetic Force
• Magnitude of Force
• Extra Example 1: Vectors
• Extra Example 2: Proton in Magnetic Field
• Extra Example 3: Proton Circular Path