Inductance and Inductors...

[Painandsuffering]

I recently joined this forum in hopes that it would help with my work at the college I'm going to. I recently started on chapter 12 of Nigel P. Cooks Introductory DC/AC Electronics fifth edition. I am finding that I am needing more help all the time so I was wondering if you guys would be able to help me with some hints and pointer as I progress I will be posting new subjects If I need help with them.

 

[Russlk]

That is what we are here for. It will help if you are quite specific on what you need help on.
Since you mentioned inductance, I will try to shed some light: Whenever current flows, there is a magnetic field around the current (the right hand rule). If the wire is wound into a solonoid, the magnetic field is augmented, and the lines of force cut across all the windings. Not only does a current produce a magnetic field, but a magnetic field moving across a wire will induce a current. This induced current is always in a direction to oppose the action that caused it.

So, when current tries to increase in a solonoid, there is an opposing current caused by the lines of force trying to increase. As a result, the current increases slowly. This effect is called inductance. There is energy stored in the magnetic field: E = 1/2 *L*I^2. Where E = energy, L is the symbol for inductance, I = current.

 

[grrr_arrghh]

maybe i'm being silly, but isn't it 'flemings left hand rule'..., if you used a right hand rule, the magnetic fields would all be backwards!!

ok, so this has no bearing on inductance, but for the sake of science...

 

[ljcox]

Whether it is the right or left hand rule depends on the assumed direction of current flow. For conventional current it is the right hand and for electron flow it is the left. It is usual to use conventional flow.

Note that the "Ohm's law" of inductance is v = L di/dt compare with the "Ohm's law" of capacitance which is i = C dv/dt.

Len

 

[Painandsuffering]

thanx for the info about the hand rules.

I have read a lot about the left hand rule and right hand rule differences from you guys and thanx and the info on finding energy is a big helper. I could really use some help in figuring out the arc tan function on my ti-83 plus because for some reason whenever I use it to find theta I come up with a number that isn't even in degrees and I have to go borrow my instructors scientific calculator in order for me to take a test which makes things really difficult since I'm used to my ti-83 plus. this would really help since I can't figure out theta without it. I am good at memorizing the mathamatical equations I just need help with remembering the trivia which is the terms and such. if you wanna see a practice test go to www.prenhall.com/bookbind/pubbooks/cook2/chapter12/deluxe.html if you go there and check out the multiple choice for the trivia parts and explain these a bit it would really help me remember them since my book barely mentions them. thanx a lot guys and gals.

 

[Russlk]

I am not familiar with the TI-83, but it no doubt returns angles in radians, so you have to multiply by 180/pi. If the calculator is any good, you should be able to program it to return the angle in degrees.

 

[fat-tony]

My girlfriend has a TI-82, when I see her, I'll have a look and tell ya how to change to degrees.

 

[petesmc]

To change it to degrees, press [Mode] then down down to "Radian Degree" and press right, and then [ENTER] and thats it.

-Peter

 

[Painandsuffering]

calculator problem solved!

Thanx guys so much for helping me with my calculator. I now am getting the right readings when I put in my theta formulas. thanx a lot!!!!!! If you guys have any questions that might be in my introductory ac/dc book (also has solid state) go ahead and ask and I'll go through it and check for ya.