Magnetism+&+Induction

= Magnetism & Induction =

A magnet has two poles, a north and a south. As in every magnet, these two poles repel each other. All magnets have a magnetic field B which has SI units of Telsa. Electrical currents produce magnetic fields and magnetic fields and a changing magnetic field produces a current. For a straight wire of length l carrying a current i, the force has a magnitude F=ilBsin(theta). The theta is the angle between the magnetic field and the current. In addition, a magnetic field exerts a force on a moving charge defined as F=qvBsin(theta). F is perpendicular to v and B which allows the use of the right hand rule. Point fingers in velocity, curl fingers towards B, thumb points in the direction of the force. The magnitude of the field produced by a current in a straight wire at a distance away is given by B=u/2(pie) I/R. The magnetic field in a solenoid is given by B=uNI/L

Amperes law states that around any chosen closed loop path, the sum of each path segment times the component of B parallel to the segment equals u times the enclosed current. (torque)=NIABsin(theta).

A mass spectrometer uses electric and magnetic fields to determine the mass of an electron.

The magnetic flux(change in magnetic field per area) passing through a loop is equal to the area times the perpendicular magnetic field. (flux)= BAcos(theta) Emf= -N delta(flux)/delta t These formulas and concepts are known as faradays law of induction.

Lenz law says that the produced emf produces a current whose magnetic field opposes the original change in flux.

For a straight wire length of L moving with speed v perpendicular to a magnetic field Emf=BLv

Transformers