# Doubt in magnetism

1. Jun 21, 2007

### logearav

folks,
in higher secondary books i came across magnet's length that is bar magnet's length is given as " 2l" that is 2 multiplied by l. my question is " why the lenght is not referred as 'l' the usual way of referring length.
logesh aravindan

2. Jun 21, 2007

### arkhammedos

i am a poor one in english but iff i understund : they make that in order to have a simple formula ;because(may be) they will divid by 2 so in the place to have this ugly (l/2) they just have this beautiful (l). and i recall that in the baccalaureat exam of this year ,they gave us (2l) in order to pertutbate you .

3. Jun 25, 2007

### logearav

i dont understand please clarify lucidly

4. Jun 25, 2007

### CraigD

I would have to see the book, but I'm assuming the l is refering to the lenght of a single pole, so the total length of the magnet is 2l. That is l of the north and l of the south combined.

CraigD, AMInstP
www.cymek.com

5. Jun 25, 2007

### Mentz114

arkhammedos is right. Often the length is given as '2l' so the 2 will cancel out and leave a cleaner expression.

It is like choosing radius and not diameter so we can write $$A=\pi r^2$$ and not $$A=\frac{\pi D^2}{4}$$