List the three main things necessary to build an electromagnet.

Electromagnets are special types of magnets that are made by passing current through coils of wire. To make an electromagnet, the minimum requirements are:

1. A nail (usually made of iron, steel or zinc)

2. Dry cell batteries

3. Wire (Usually copper wire)

Other things could be:

1. Electric tape to hold both ends of the wire properly at the battery terminals.

2. Scissors to cut the wire into desired length.

3. Iron fillings for testing purposes.

the results is a decrease in air temperature with an increase of altitude.

explanation:

the bal will not change its velocity.