## Thursday, August 4, 2011

### Intro into Electronics Part 1 DC

I had a friend who called me crazy for pursuing a engineering degree emphasized on electronics. He was pursuing an engineering degree focused on metallurgy. He claimed that the way circuits work is magic. I claim that it is not that hard. So in this blog post, I will give a basic intro into the theory behind circuits.

First we should go over some definitions:
Voltage-V it is  energy per unit charge measured in volts
Current- I it is the rate of flow of charge measured in amperes/amps
Resistance- R it is the property of the material that hinders the current measured in ohms

If you have ever taken a class in electronics you will recognize this next image it is the water analogy.

This image pretty much explains Voltage resistance and current. So now, lets go over a couple of equations.
1. Ohm's Law V=IR so Voltage = Current x Resistance. This is the most basic equation in electronics. So for a given wire size (with known resistance), if the voltage is increased then the current must also be increased.
2. Power P=IV or Power = Current x Voltage. You can substitute Ohm's law and get P=I^2 R and so on. Power is either absorbed by an element or delivered by an element. Whether Power is delivered or absorbed depends on the passive sign convention.

THE PASSIVE SIGN CONVENTION

The passive sign convention is very important in circuit analysis. If you do not follow it you will get wrong voltages and currents and ect... in your calculations.
The passive sign law states: When current enters the positive terminal then the element absorbs power. If the current leaves the positive terminal then the element delivers power.

That is all I am going to cover for now. Next time I will go over some basic ways to analyze simple circuits. (preview KCL and KVL) and I may also throw in a introduction to a component. Always open for questions and corrections I am a student and not perfect but would like to share what I have learned

1. good info here! physics was my favorite subject in school. +followed

2. thanks for the intro :D

3. Very cool. Thank you!
+following

4. This is so over my head, but interesting!

5. Oddly enough I had a problem today explaining the difference between current and voltage to someone, I will forward them your informative post, thanks! Keep it up

6. i learned something today. thanx

7. You have no idea how helpful this is to me.

9. Might consider pointing my to-be engineer buddy over here.

10. Thanks for the responses. Voltage and Current can be hard to explain if you are talking to someone who does not know much about them. Side note electrical engineers follow current in the opposite direction compared to physics majors.

11. Dang, you know your stuff. I'll be checking back for sure.

12. You've lost me but kudos for making an accessible source for info on this.

13. Wow, what an excellent post; I wasn't expecting an electronics lesson! :P
Following.

14. One day this is going to help me with something... I'm sure of it :p

I may be doing some wiring for my car soon so this cant hurt!

15. I wired up my speakers, subs, amp, and my stereo check out crutchfield.com usually has best deals and comes with good instructions

16. i took an electronics summer class and it was the single most confusing class i've ever taken

17. god i wish i knew what you knew

18. Great explanation. :)

19. This stuff is simple, wait until he gets into phase angles.

20. @ Dwrek yes phase angles are tough and I am not sure if I will go that far in this blog as most readers probably do not understand differential equations.

21. Good to know, thanks!

22. You totally lost me after the 5th technical word, but hey, I'll follow, because maybe i can learn a decent thing or two from this blog!