How do you change the strength of a electromagnet

The strength of an electromagnet can be increased by increasing the number of loops of wire around the iron core and by increasing the current or voltage. You can make a temporary magnet by stroking a piece of iron or steel (such as a needle) along a permanent magnet.

There are three things that dictate how strong this field is:

1.How much kinetic energy you provide the wire

Answer is changed by pushing more current through the wire.

2. How permeable our magnetic rod is

Answer  is changed by picking a more magnetic media

3.How many little magnetic fields you generate to make the net, large magnetic field

Answer is changed by increasing the amount of turns of the wire. More turns, more little fields, strong big field

the answer is kevlar

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.