# A coil with turns given magnetic field, time find the emf induced in the coil

#### sonrie

A coil with 240 turns enclosing an area of 13.7 cm^2 is rotated in a time interval of 3.70×10^-2 s from a position where its plane is perpendicular to the earth's magnetic field to one where its plane is parallel to the field. The earth's magnetic field at the lab location is 5.9×10−5 T .

What is the total magnetic flux through the coil before it is rotated?
I found this answer its 1.9*10^-5 WB.

What is the total magnetic flux through the coil after it is rotated?
I found this answer its 0 WB.

What is the average emf induced in the coil?

I'm having trouble getting the right answer! I get 1.27*10^-7 but its wrong! Help Please!

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#### Doc Al

Mentor
What is the total magnetic flux through the coil before it is rotated?
I found this answer its 1.9*10^-5 WB.
Double check the exponents in this answer.

What is the total magnetic flux through the coil after it is rotated?
I found this answer its 0 WB.
Good.

What is the average emf induced in the coil?

I'm having trouble getting the right answer! I get 1.27*10^-7 but its wrong!
How did you get this?

#### sonrie

the equation is emf = -N BA/T

-240 5.9*10^-5*.137/5.9*10^-5=3.28*10^-9 its still wrong

#### Doc Al

Mentor
the equation is emf = -N BA/T

-240 5.9*10^-5*.137/5.9*10^-5=3.28*10^-9 its still wrong
You have the correct formula, but you need to redo the calculation more carefully:
(1) You have the incorrect area. (Note that 1 cm^2 $= 10^{-4}$ m^2.)
(2) Divide by the time interval.

Thank you!

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