[问答题]
List the three ways tuov4cbi-2 u. ,dxdch,gsu x9*h:tc/cwh0v;lrkix , 9r at 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
