list of awesome formulas2ndlongexam

8/13/2019 List of Awesome Formulas2ndLongExam

1/15


2/15

Magnetic field is established byPermanent magnetElectric current in a magnetMoving charge

There is NO MAGNETIC MONOPOLEA moving charge (current) creates a magneticfield in the surrounding spaceThe magnetic field exerts a force on any other

moving charge /current that is present in the field


3/15

MAGNETIC FORCE= proportional tothe charge, velocity and magnetic

field.


4/15

SOME NOTES ON MAGNETIC FIELD LINES


5/15

F B = q( v x B )

MAGNETIC FORCE ON A MOVING CHARGED PARTICLE

When theparticle is

at rest,the

magneticforce is

equal toZERO

When the velocityand the magnetic

field are parallel/antiparallel to eachother (perpendicularcomponent is zero),

FB is zero.


6/15


7/15

Magnetic Flux,B = surface B cos dA

= surfaceB

dA

= surface B d A= B A= [Tesla meter 2

, T m 2 ]= [ Weber, Wb]

MAGNETIC FLUX

Unitflux=1Wb=1T(m 2)=

1Nm/A


8/15

Magnetic Field/Magnetic Flux density=flux per unit area across an area at right angles to the

magnetic field


9/15


10/15

2

11

1

22

2102112

1

212

2

121

i N

i N M

l

A N N M M M

dt

di

M dt

di

M

MUTUAL INDUCTANCE

EQUAL M, differentchanges in current

Negative signs are a reflection of lenzs law.

These saythat a

change incurrent in coil

1 causes achange in

flux in coil 2,inducing anemf in thecoil 2 that

opposes theflux change.


11/15

SI unit of inductance is called theHenry=1 weber per ampere

=one volt second per ampere=one ohm-second=1 joule per ampere squared

Examples:A. If a tesla coil has a long solenoid with length l and cross sectional area A is

closely wound with N1 turns of wire, and another coil with N2 turns surroundsit at its center, find the mutual inductance.

= N1N2A l

B.


12/15

SELF INDUCTANCE-in a circuit, when there is current, there is a magnetic field,that causes a magnetic flux, that changes when currentchanges :D THEREFORE any circuit that carries a varyingcurrent will have an emf induced by the variation in its ownmagnetic field.

l

A N L

i

N L

dt

di L

SOLENOID

2

0

1

Notice that whenwe transposedi/dt, the self

inductance is justequal to the emf

per unit rate ofchange of

current.

Inductors=purpose is to oppose any variations in the current throughthe circuit

Depends on geometry: size,shape and N

Proportional to Nsquared


13/15

Between the terminals of an inductor, the potential difference is

equal to : V ab = Va Vb = L (di/dt)


14/15

MAGNETIC FIELD ENERGY

2

2

LI U M

Stored energy in an inductor


15/15

list of awesome formulas2ndlongexam

Documents