Force on an Electric Charge Moving in a Magnetic Field

F=qvB sin

Right-Hand Rule Again

Important: right-hand rule defines direction of a force acting on a positive charge. For negatively charged particles the force is in exactly the opposite direction.

Don’t forget this when you are solving problems about electrons!!!

Electron’s Path in a Uniform Magnetic Field

An electron travels at velocity v in a plane perpendicular to a magnetic field. Describe its path.

Conceptual Example: A Spiral Path

What is the path of a charged particle if its velocity is not perpendicular to the magnetic field?

Magnetic Field Due to a Straight Wire

AmT

r

IB

/104

27

0

0

Force between Two Parallel Wires

Each current produces magnetic field that is “felt” by the other wire so that each must exert a force on the other.

Parallel current in the same directions attract each other, antiparallel currents repel.