Answer:
A. Increasing the current flow
B. Putting a piece of iron inside the loops of wire
C. Increasing the number of loops of wire
Explanation: An electromagnet is a device which has conducting wire coiled around a piece of metal usually an iron core. The metal acts as a magnet when current passes through the wire. The strength of the magnetic field depends upon the amount of current and number of loops of the coiled wire. Thus, if a piece of iron is placed inside the loops of wire, current is increased and number of loops is increased, the magnetic field strength increases.
