Physics help!

Question

A small loop of wire with radius 2 cm is placed in a uniform upward magnetic field. By what factor does the flux change if the radius of the loop is increased to 8 cm?

 

 

Answer 1

The flux is directly proportional to the magnetic force applied & inversely proportional to the area of the figure. Since the figure is a loop (circle), the area of the loop would be pi * r^2. The radius has increased from 2 cm to 8 cm. That means the radius has quadrupled & in turn the area has increased 16 fold. This means the flux has become 1/16 of what it original was when the loop was 2 cm.