# dynamically induced emf

Discussion in 'Homework Help' started by devin, Apr 28, 2008.

1. ### devin Thread Starter New Member

Apr 28, 2008
1
0
when a magnetic field is stationary and the conductor is in motion then the induced e.m.f is called dynamically induced e.m.f

suppose the conductor moves at an angle (alpha) with the direction of the magnetic flied then the velocity v is resolved into 2 components v cos (alpha) and v sin (alpha)...
vcos(alpha)being parallel to the field doesnt induce any voltage....

this is followed by a worked example..
in which they say
1>a square coil of 10 cm side with 100 turns is rotated at a uniform speed of 100 rev/min.............calculate the instantaneos value of induced e.m.f when the plane of the coil is
a> at right angles to the field
b>at 30 degree to the field
c>in the plane of the field

in the solution they say
a>when the coil is rotated at right angles to the field the coil sided dont cut the flux so the induced emf is zero...

but is it not like the flux is cut maximum then the coil is rotated at 90 degree?

b>the angle between the direction of motion of the conductor at the field is 60 degree..and the use the formula and use 60 degree...

in the question it says 30 degree..y did they use 60 ,does the direction of the field should be taken into account while measuring the angle at which its inclined? and y?

c>the conductor cut the flux at right angles hence maximum emf is induced

its the same as first question..

please help me understand and if possible can some one gimme link to a 3 dimentional figure as to how it works ..thanks for reading

2. ### techroomt Senior Member

May 19, 2004
198
1
first, learn and apply flemings rule. now imagine a magnetic field with parallel lines of flux, say going left to right. if a conductor were to travel in this field in a circular motion, it would cut the lines of flux at different rates. as mentioned, when going perpindicular to the flux lines the rate would be highest (peak), and when traveling parallel to the lines, the rate would be zero (crossover). at that time the conductor would change directions (polarity reversal) and cut lines of flux in the opposite direction. the circular motion and rate change of flux being cut is what generates the sine wave ac output.