Calculating Strength of a magnet

 Magnets are everywhere. They can be permanent magnets or electromagnets. Magnets come in many shapes and sizes but they also come in different strengths. 

It depends on what is meant by strength.  Two common measures of a magnet’s strength are the strength of the magnetic field and pull force. 

The magnetic field strength is expressed in Gauss or Tesla (1 Tesla = 10,000 Gauss).  It depends on the size, shape, grade of the magnet and where the measurement is performed.

We will use a magnetometer sensor available in this smartphone to measure the strength of the magnetic field.  Science Journal App is used to visualize data captured by the sensor. 

As We move the bar magnet near the sensor, the strength of the magnetic field goes up. It comes back to original value as I move the bar magnet away. Same is true for other pole as well. 

Electromagnet also behaves in a similar manner. We can see the proportional increase in strength with increase in current. 

What if you don't have a magnetometer ? You can design your own scale with everyday things and compare the strength of the magnetic field quantitatively.

I will take this small steel ball and place it at a distance. I will slowly move the magnet towards the ball. The point at which ball is attracted towards the magnet is noted. We can note it down and compare the strength of all the magnets we have. Off-course this is our local scale. 

Another way is to place a magnet in the bowl filled with balls and measure how many are attracted. By calculating the average, you can arrive at some number.

We can also compare strength based on the weight magnet can lift as well. 

Let us attach this magnet to the wooden base here and calculate pull force. This nut with a container is stuck to the magnet. We will put balls in this container till it pulls the magnet down. This will be one measure of the strength of the magnet.

Same can be tried with a Neodymium magnet as well. It seems we need more force to pull the nut down. Let us tie this bottle and increase the force by adding water. It took 700 ml of water or approximately 7 Newtons.

You can try these variations to calculate the strength of the magnetic field. 

Thank You.