Answer:
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.
Answer:

Explanation:
As we know that resistance of one copper wire is given as

here we know that

now we have


now we know that such 17 resistors are connected in parallel so we have


Now if a single copper wire has same resistance then its diameter is D and it is given as

now from above two equations we have


now we have

In our Solar System, Jupiter is the largest planet we have. it has the surface area of 23.71 billion mi^2. it beats all the other planets in both mass and volume.