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# magnitude of induced emf problem . watch

1. Hi guys.
i've managed to do all parts of the blow question but for the last part i keep getting wrong answer . any help?
a circular coil of diameter 24mm has 40 turns. the coil is placed in a uniform magnetic field of flux density 85mT with it's plane perpendicular to the field lines. if the coil was reversed in a time of 95ms calculate:
the magnitude of the induced emf. i've used the formula (change of flux/time T)xN but i keep getting wrong answer. here's other informations i've managed to calculate in other parts of the question:
A=4.52X10^-4
the change of flux linkage through the coil =3.08Wb.
2. (Original post by Alen.m)
Hi guys.
i've managed to do all parts of the blow question but for the last part i keep getting wrong answer . any help?
a circular coil of diameter 24mm has 40 turns. the coil is placed in a uniform magnetic field of flux density 85mT with it's plane perpendicular to the field lines. if the coil was reversed in a time of 95ms calculate:
the magnitude of the induced emf. i've used the formula (change of flux/time T)xN but i keep getting wrong answer. here's other informations i've managed to calculate in other parts of the question:
A=4.52X10^-4
the change of flux linkage through the coil =3.08Wb.
The formula you need is:

where:

3. where A is concerned, can i just use the equation for calculating area of a circle?(pi r^2) .
i don't really understand what each alphabet stands for for the equation you mentioned to calculate A
4. (Original post by Alen.m)
where A is concerned, can i just use the equation for calculating area of a circle?(pi r^2) .
i don't really understand what each alphabet stands for for the equation you mentioned to calculate A
Yes, it's simply the area enclosed by the coil so

flux density.

number of turns in the coil.

calculated from 2 x 95ms period (1 complete rotation).
5. But angular velocity is equal to 2piF isn't?i did the area exactly like you mentioned but still the answer i got is different that what the text book says which is 33mv

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