PHYS 270 – SUPPL. #6

DENNIS PAPADOPOULOS

FEBRUARY 11, 2010

Hydro-Electric Station

www.opg.com/power/hydro/howitworks.asp Watch movie at

FE FB dqdE dqvBdE parallel to the bar and across dE

v =r dE =rB

For uniform E - field V = Ed

dV = dEdr =Brdr

V =B rdr =l2

20

l

B

Hydroelectric Power

From last lecture

TETHERED SATELLITE SYSTEM

EMF=vlB= (8 km/sec) (20 km)(.3 x10-4 T)=4.8 kV

R= 4.8 kV/1A=4800 Ohm P=I(EMF)=4.8 kW

Falling magnet slows down as it approaches a copper ring immersed in liquid Nitrogen

Why ? and what is the use of liquid Nitrogen ?

Falling magnet slows down as it approaches a copper ring immersed in liquid hydrogen

Insert movie for falling magnet

MAGNETIC FLUX CONVENTIONS

cos

BA

UNIFORM B

AdB

AdBd

NON-UNIFORM B

N number of loops in a coil

What about the minus

sign ?

LENZ’s LAW APPLICATION

Falling magnet – changes Magnitude

of B

Copper Ring

Falling towards a

dipole magnet

Will be discussed in detail during recitation

EDDY CURRENTS

Induced currentcauses force

LOOP CURRENT BY TEMPORAL FLUX CHANGE –LENZ’s LAW

FARADAY’s LAW

dt

BdA

dt

AdB

dt

d

GENERATORS – TRANSFORMERS- DETECTORS

m ABcos ABcost

coil N dm

dtABN sint

dm

dtconst

1

N1

V1 1

N2

V2

V2 N2

N1

V

MAGNETIC FLUX

IS THE ANGLE THE AXIS OF THE

LOOP MAKES WITH THE

DIRECTION OF B