[问答题]
List the three ways tj2t 8(wl;h fx-yas od,ftg.p+hatsimijc+ds( vx tpvg: o0d- 2)( an $emf$ can be induced in a loop of wire.
参考答案: 1. by changing the magnetic field
2. by changing the area of the loop in the field
3. by changing the loop's orientation with respect to the field
