How to make an electromagnet?

An ordinary bar magnet has a magnetic field around it all the time. We call this kind of magnet a permanent magnet. You can also make a magnet by wrapping wire around an iron rod or bolt. When an electric current passes through the wire, the rod works like a magnet. We call this kind of magnet an electromagnet. We use electromagnets in many household appliances, such as refrigerators and vacuum cleaners.

How to make a electromagnet?

1. Line up the compass needle so that it points to the north. Place it near one end of the ruler, with the ruler facing east- west.
2. Now make an electromagnet by winding the 20-inch (50-centimeter) wire many times around the bolt. Always wind the wire in the same direction. Leave about 4 inches (10 centimeters) of wire free at each end. Place the electromagnet facing east-west on the ruler near the compass

3. Connect the electromagnet to the “D” battery and watch the compass needle. It should swing towards the electromagnet. If it doesn’t, move the electromagnet closer to the compass.
Where does the electromagnet have to be on the ruler to make the compass needle point halfway between the N and the W? Mark this point on the ruler.

4. Now make a second electromagnet with the longer wire, leaving about 6 inches (20 centimeters) of wire free at each end. Disconnect the first electromagnet. Place the second one on the ruler at the mark you made earlier, and connect it to the “D” battery.

What happens to the compass needle?
Does it swing around farther than before?
Remember, twice as much wire means twice as much resistance. This makes the current half as strong.

How to make an electromagnet stronger?

What can you learn from the experiment on this page?
The strength of an ordinary bar magnet is permanent and fixed.
But we can make the magnetism around an electromagnet weaker or stronger, and we can even turn it off completely.
How can you make an electromagnet stronger? 
How did you increase the magnetism in the electromagnet?

The electromagnet has become stronger because the 6-volt battery is sending more electric current through it.
More electric current makes an electromagnet stronger.
The needle moves farther than before.