Gabriel used an iron nail to build an electromagnet (like the one seen below) that will pick up 4 paper clips. He has tried many changes to increase the strength of his electromagnet so that it will pick up 10 paper clips? For each of the following changes, predict and explain the most likely outcome for 2 points each:

Replacing the iron bolt with a plastic rod
Increasing the number of coils in the copper wire
Increasing the size of the battery