• Mr Ausome

Alternative Method to Fleming's Left Hand Rule of Electromagnetism

Before our math tuition class today, I noticed one of my students doing her physics electromagnetism revision for her upcoming O-level prelims and had difficulty executing the Fleming's Left Hand rule. Although it was not a math topic, I decided to giving her a helping hand. The biggest problem she had was that she could not fix the position of her three fingers!

As such, I came up with an alternative method to the Fleming’s Left Hand Rule. I shall name it the Alvin Au’s Ruler Technique of Electromagnetism (AARTE). I have tried and tested the method on electromagnetism questions and it proved to be helpful to my student who had difficulty with the Fleming's Left Hand rule.

Firstly, you need to create your tool (which is a ruler):

1) Pick one corner of the ruler to be the origin position

2) Get someone who is familiar with Fleming’s Left Hand Rule to help you with drawing the following arrows on your ruler:

Red (Fire) represents the Force Direction

Blue (Marine) represents the Magnetic Field Direction

Black (Charcoal) represents the Current Direction (Note that Dot represents current coming out of plane and Cross represents current going into the plane)

After creating the ruler, we tried it on several of the homework questions and it proved to be useful:

The electromagnetic force for the above question is downwards (Red Arrow)!

The electromagnetic force for the above question is upwards (Red Arrow)!

Key tips to using this alternative FLHR method:

1) Remember that the Fleming's Left Hand Rule is about the relationship between 3 directions (Magnetic Field, Current and Force), hence you always have to align 2 of the given directions in order to find the last one using this method.

2) Be flexible with rotating the ruler in all planes and directions but do not lose track of the origin corner as the point of comparison.

3) Practice a lot on many different kinds of questions to fully master it.

4) Use a permanent marker to draw on the ruler.

5) To use it for Fleming's Right Hand Rule of electromagnetic induction, simply use it as per normal but take the reverse direction of whatever you obtained.


The AARTE is an unorthodox method that I have just invented and is definitely not in the mainstream syllabus yet. Hence, use with caution because your teacher might deem this method as cheating!

Check with your teacher before using! Feel free to direct them to this website.

To get professional help (Math tuition) on secondary school mathematics in Singapore, click here.

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Mr Ausome

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