What can be increased in order to increase the magnetic field?
The size of the iron core
The magnetic poles
The wire resistance
The current

Question

What can be increased in order to increase the magnetic field? 
    The size of the iron core 
   The magnetic poles 
   The wire resistance 
   The current

jamesj · Answer

what can be increased in what?  For example, a wire conducting electricity generates a magnetic field, so "The current" is correct.

But if you have a piece of magnetized iron, then increasing it will also make the magnetic field stronger.

anonymous · Answer

the wire resistance and the current both have to be increased to increase the magnetic feild   as the flow of electrons increase the charge flows faster and there is an increase in magnetic feild