Px157 Revision Flashcards
(18 cards)
What is Kirchoff’s loop rule?
Over a closed circuit the sum of voltages from sources of emf equals the voltage drop across all other components
What is Kirchoff’s junction rule?
At a junction where several wires meet the total current is zero
What is Gauss’s law?
Double integral over closed surface s of vector E•dS = Qencl/epsilon0, where E is electric field vector, Qencl is total change enclosed by volume of surface s, epsilon 0 is permittivity of free space, dS is the vector normal to the surface outward
Formula for potential in an electric field?
V(a) - V(b) = integral from b to a of E.dr
What is the magnetic Lorentz force formula?
F = qv(drift) x B
What is amperes law?
Integral over a closed surface of B•dl = mu0 I(encl)
What is Faraday’s law?
Induced imf is equal to - d(magnetic flux)/dt
What is the formula for magnetic flux?
Øb = double integral over a surface s of B•ds
What is the formula for motional emf?
Closed integral of (v x B•dl)
What is the force on a current carrying wire due to a magnetic field?
Integral between L and 0 of I•dl x B
What is the solenoidal condition?
Double integral over a closed surface S of B•ds = 0
What is a key takeaway from the biot savart law?
Magnetic field is perpendicular to current
What does the solenoidal condition imply when magnetic field in the direction of the current is 0?
Magnetic field in the radial direction is zero
What is the formula for energy stored in a magnetic field?
U = 1/2 * L * I^2
What is ferromagnetism?
The magnetic susceptibility»_space; 1 and the material is spontaneously magnetic
What is diamagnetism?
Magnetic susceptibility < 1 and the magnetisation opposes external fields such that the internal field is less than the external
What is paramagnetism?
Magnetic susceptibility > 1 such that the magnetic field inside the material is greater than that applied to the material
What are the three magnetisation formulae?
B = mu0 (H + M)
B = mu0 muR H
M = ki H
