Direction of the induced current- Right Hand Rule?

Question

The drawing shows that a uniform magnetic field is directed perpendicularly into the plane of the paper and fills the entire region to the left of the y axis. There is no magnetic field to the right of the y axis. A rigid right triangle ABC is made of copper wire. The triangle rotates counterclockwise about the origin at point C [ which has the coordinates (0,0).] What is the direction (clockwise or counterclockwise) of the induced current when the triangle is crossing each of the following axes? Justify your answers in each case.

**The triangle is in quadrant I with A-C on the positive y axis, B-C on the positive x-axis, and A-B making the hypotenuse,

a. the +y axis

b.the ‐x axis

c.the ‐y axis

d. the +x axis

Thanks!

Answer 1

Look at the flux in this problem.  What direction is it, and is it increasing or decreasing at the moment of interest?  Whichever way flux is *changing* will tell you which way the induced field will go, as the induced field will oppose the change in flux (so if you have more flux upward, you'll get a field downward).

Once you have the direction of the induced field, you use the RHR to see what direction current would have to flow around the loop to make such a field.