[问答题]
List the three ways 1lthq imwdbdw15* b( (/tz c;6ow p uj1l/.xkjthat 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
