emf (1 Viewer)

[=)(=]

answer is A

This seems like complete garbage cause the dash of cos is -sin and so the dash of -cos is just sin so it should be c right?

 

[yanujw]

When you explained your working did you mean dash as in derivative? If so, you have the right theory but remember that emf is opposite to the direction of change in flux, as represented by the flux formula. Therefore it is A, which you will notice is the negative of C.

 

[chilli 412]

View attachment 37924
answer is A

This seems like complete garbage cause the dash of cos is -sin and so the dash of -cos is just sin so it should be c right?

hopefully this helps (i haven't covered this topic yet, sorry for any issues) , but using this:


we know that emf is -1 * (number of revolutions) * (the derivative of flux with respect to time)
we know that our number of revolutions = 1
therefore emf = -1 (phi') (side note: here, phi' just means the derivative of flux with respect to time)
now looking at our given graph, we can tell this is the graph of -cos(t)
therefore, phi = -cos(t)
this means that phi' = sin(t)
since emf = -(phi'), this means that emf = -(sin(t))
therefore emf = -sin(t), which corresponds with option A

 

[=)(=]

Thanks guys makes sense