A wire is placed between the poles of a magnet.
Which statements are correct?
An a.c. current in the wire causes a changing force on it.
A downward d.c. current in the wire causes a constant force on it.
An upward d.c. current in the wire causes a constant force on it.
1 and 2 only
1 and 3 only
2 and 3 only
1, 2, and 3
