W. Sautter 2007

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N

+

Fingers = magnetic flux lines North to South

Thumb = directionof + charge

Motion (current)

Palm = forceExerted onThe charge

Centripetal forceOn charge causedBy magnetic field

Charge moves in a circular path

N (magnet) S

By convention (everybody agrees) lines of magneticFlux leave the North pole and enter the South pole

Lines of flux are continuous and do not intersect each other.

LENZ’S LAW

When a magnet induces a current flow in a conductor, the induced current flows in a direction so as to create a magnetic field in the

conductor that opposes the original magnet field

N SMotion of magnet

Current in loop

ConductorWire loop

Direction of inducedfieldN

Using the Right Hand Rule

Direction of conventionalcurrent flow (fingers)

North end ofInduced Magnetic

Field (thumb)

N

Fingers = magnetic flux lines North to South

Thumb = directionof induced current

in the conductor

Palm = motionof conductor

in magneticfield

Conductor isMoved upward

In magnetic field

Induced EMF

0u

2 r

F = Force (newtons)B = Magnetic field strength (teslas)

Tesla = N / amps x metersL= conductor length (meters)

V = velocity of conductor thru field (meters/sec)Q = charge quantity (coulombs)

= angle between conductor and fieldmeasured from the perpendicular (degrees)

r = distance from the magnetic field source (meters)u0 = permittivity constant of material

(Free space = 8.85418782 × 10-12 m-3 kg-1 s4 A2 or 8.85418782 × 10-12 T x m /A

n = loops of conductor

PrimaryVoltage in

SecondaryVoltage out

n= number of turns ofwire in the coil

n voltage in coil

Voltage in coil current in the coil

current

Magnetic

field

Primarycoil

current

Secondarycoil

The magnetic field caused by thechanging current in the primarycoil radiates across the secondary

coil and induces a current in it.

A continually changing current in the primary is required fora transformer to work (D.C. will not work)