What is the source of the magnetic field in a permanent magnet? A) the spin and orbital motion of electrons
B) long-range electric currents that are always present in iron
C) the motion of iron nuclei
D) net electric charge at the poles of a magnet

The stopwatch used by a student to measure velocity of a pulse in a slinky was of least count 0.1 second. he stops the stopwatch when a pulse has made 3 journeys from one end to the other of the slinky. he finds the seconds hand to be at 52nd division. calculate the correct time noted by him.