You may have heard the phrase "opposites attract". While not the best advice when it comes to relationships, this cliché is the golden rule for magnet polarity. Since we inhabit a gigantic magnet, the Earth, understanding magnetic polarity on a small scale will help you understand the larger magnetic field that protects us from space radiation. Whether it's to label your magnets for future use or to complete a fun experiment, here are some easy ways to know the polarity of your magnets.
Method 1 of 3: Using a Compass
Step 1. Gather the materials
All you need is a compass and a magnet. Any type of compass will do, but the simplest magnets to use with this method are disk or bar magnets.
Step 2. Test your compass
Although the north-pointing needle tip is usually the red one on a standard compass, it's a good idea to check. If you know where geographic north is from your current location, you can easily see which tip of the needle points to it.
- If you're not sure where geographic north is, you can determine which point indicates it by leaving your house at midday, when the sun is at the highest point in the sky. Hold the compass straight in your hand with the southern tip closest to your body.
- Note the position of the compass needle. If you live north of the Earth's equator (ie, the Northern Hemisphere), the north of the needle will be pointing towards you, and the south will be pointing towards the sun. If you live south of the equator, the south end of the needle will face you.
Step 3. Place the compass on a flat surface such as a table
The surface must not contain metallic or magnetized materials as they are capable of causing a false reading. Even objects like a keyring or a penknife can interfere with the experiment. You will notice that the north end of the compass will be pointing to geographic north.
Step 4. Place the magnet on the table
If using a disk magnet, the north and south poles will be on the two flat surfaces. If using a bar magnet, the poles will be one at each end.
Step 5. Bring the magnet closer to the compass
In the case of the disk magnet, you will need to stand it up and hold it with your index finger so that one of the flat sides is facing the compass.
If using a bar magnet, place it perpendicular to the compass so that one end of it is close to the object
Step 6. Look at the compass needle
Since this needle is a small magnet, the south tip will be attracted to the north pole of your magnet.
If the north end of the needle is pointing towards your magnet, you've found its south pole. Rotate the other side of the magnet towards the compass; the south end of the needle will now point directly to the north pole of the magnet
Method 2 of 3: Creating a Compass with Your Bar Magnet
Step 1. Find a piece of rope
You can use any type of rope you have around the house, such as wool or wrapping ribbon. The rope needs to be long enough to be tied around the magnet and suspend it.
One meter of rope will suffice in most cases. You can estimate the footage by holding the rope with both hands. With your right hand, hold the string at nose height. Extend your left arm as far as possible. The length of the rope between your left hand and your right hand is about 1 m
Step 2. Tie the string tightly around the bar magnet
Make sure the rope is securely tied so that the magnet does not slip out of the knot. Note that this method is not suitable for spherical or disk-shaped magnets.
Step 3. Hold the cord away from the body
Leave the magnet free to rotate, without contacting any obstacles. When it stops spinning, the north-facing tip is the north pole of the magnet. You just made a compass!
Note the difference from the previous method, where the south end of the compass needle is attracted to the north pole of the magnet. When using a magnet as a compass, the north pole of the magnet points north because what we call the North Pole is actually "the north-seeking pole", which is attracted to the south pole of the Earth's internal magnet
Method 3 of 3: Floating the Magnet
Step 1. Gather the materials
This method requires some household items that you probably have on hand. If you have a small magnet, a piece of Styrofoam, water, and a glass, you can do a fun experiment that will help you figure out the polarity of your magnet.
Step 2. Fill a glass, bowl or small plate with water
You don't need to fill it all the way up, just enough for the styrofoam to float freely.
Step 3. Prepare the Styrofoam
It needs to be small enough to fit in the water dish and big enough to hold the magnet. If you have a large piece of Styrofoam, you can cut it to the right size.
Step 4. Place the magnet over the Styrofoam and put everything in the water
The Styrofoam platform will rotate until the north pole of your magnet is pointing north.
- If you need to check the polarity of magnets frequently, you can also purchase a magnetic pole detector to find out which poles are effortless.
- Any magnet whose polarity you already know can be used to help you know the polarity of another magnet. The south pole of one magnet will snap to the north pole of the other.