Magnetic Fields and Forces

Facts about Magnetism

Magnetic Field

ExampleParticle 1, with a charge q1 = 3.60 μC and a speed of v1 = 382 m/s,

travels at right angles to a uniform magnetic field. The magnetic force it experiences is 4.25 x 10-3 N. Particle 2, with a charge of q2 = 5.30 μC and a speed of v2 = 1.30 x 103 m/s, moves at an angle of 55.0º relative to the same magnetic field. Find (a) the strength of the magnetic field and (b) the magnitude of the magnetic force exerted on particle 2.

Direction of the magnetic force?

Right Hand RuleTo determine the DIRECTION of the

force on a POSITIVE charge we use a special technique that helps us understand the 3D/perpendicular nature of magnetic fields.

•The Fingers =•The Thumb =•The Palm =

ExampleDetermine the direction of the unknown variable for a proton

moving in the field using the coordinate axis given

Charges moving in a wireUp to this point we have focused our attention on

PARTICLES or CHARGES only. The charges could be moving together in a wire. Thus, if the wire had a CURRENT (moving charges), it too will experience a force when placed in a magnetic field.

You simply used the RIGHT HAND ONLY and the thumb will represent the direction of the CURRENT instead of the velocity.

Applications of CCW being deflected in a Magnetic Field

Calculating Force on a CCW

ExampleA 36-m length wire carries a current of 22A running from right to left. Calculate the magnitude and direction of the magnetic force acting on the wire if it is placed in a magnetic field with a magnitude of 0.50 x10-4 T and directed up the page.

WHY does the wire move?The real question is WHY does the wire move? It is easy to

say the EXTERNAL field moved it. But how can an external magnetic field FORCE the wire to move in a certain direction?

Determining the direction of the magnetic field around a CCW

Using the magnetic field from a wire, an electromagnet can be produced.How does it work?