Magnetic Flux

The product of magnetic field (B) and area (A). Can be thought of as a total magnetic “effect” on a coil of wire of a given area. B A

Maximum Flux The area is aligned so that a vector perpendicular to the area points parallel to the field B A

Minimum Flux The area is aligned so that a vector perpendicular to the area points perpendicular to the field B A

Intermediate Flux The area is neither perpendicular nor is it parallel B A

Magnetic Flux  B = B A cos  –  B : magnetic flux in Webers – (Tesla meters 2 ) – B: magnetic field in Tesla – A: area in meters 2. –  : the angle between the area and the magnetic field.  B = B  A

Sample Problem Calculate the magnetic flux through a rectangular wire frame 3.0 m long and 2.0 m wide if the magnetic field through the frame is 4.2 mT. a)Assume that the magnetic field is perpendicular to the area vector. b)Assume that the magnetic field is parallel to the area vector. c)Assume that the angle between the magnetic field and the area vector is 30 o.

Sample Problem Assume the angle is 40 o, the magnetic field is 50 mT, and the flux is 250 mWb. What is the radius of the loop? B A

Induced Electric Potential A system will respond so as to oppose changes in magnetic flux. A change in magnetic flux will be partially offset by an induced magnetic field whenever possible. Changing the magnetic flux through a wire loop causes current to flow in the loop. This is because changing magnetic flux induces an electric potential.