[问答题]
List the three ways b94d3nm7ayi5kl s9vj - -vxz4 mjn0hot6,c;fsz )m61nkl osbuhat 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