Magnets

b=uI/2piR
r=radius
Because if the radius is on the numerator earths magnetic field will dominate ..

entire loop ==
b=uI//4piR^2

difference across the plates is V.
The electric field between the plates is E =
V/d, and therefore D = εE/d.
c=εA/d

mAGnetic field B = μI/(2πr)

F = NbIB.
τ = NAIB sin θ

magnetic field in the center
B=UI/4πR^2*2πR
B=UI/2R

Lenz's Law:
FIGURE X.2


When an EMF is induced in a circuit as a result of changing magnetic flux through the
circuit, the direction of the induced EMF is such as to oppose the change of flux that causes it.