An electromagnet is created using a battery, an insulated copper wire and an iron nail. the wire is wrapped around the nail 20 times and attached to the battery. which pair of changes will definitely increase the strength of the electromagnet?

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I'm having some difficulty seeing the diagram clearly.but the question says there's a net inward force on the object.so we know right away,  from newton's 2nd law of motion, thatthat baby is accelerating.  it doesn't even matter which way thenet force is pointing.  if there's any net force, then either theobject's speed or else its direction must be changing.