I love Science and maths :D This blog i will post random parts of my As levels that will teach you how to do As chemistry, physics and maths :)

Wednesday, 6 April 2011

Current and Charge

Charge carriers are a charged particle. Current in a circuit is induced by the flow of these charge carriers. Current is defined as the rate of flow of charged particles in a wire or component.
In a metal the charge carrier is an electron which is free to move around the molecule colliding with each other and positive ions within the metal.
In a salt solution the charge carrier is a ion, an ion is a charged atom or molecule.

Convention of current
Originally before the discovery of electrons it was believed that current flowed from positive to negative within the circuit, when in fact its negative to positive. (This is because electrons are negative being repelled by the negative side and attracted to the positive side of the cell/battery.)

∆Q = I∆T
I x T = Electrons passing a point in used time

Worked example

A) If the charge flow is 50C and the current is 10A what is the time taken for this amount of charge to pass a point in the circuit?

B) How many electrons pass through the circuit in this time?

Using equation ∆Q = I∆T

Rearrange it to find time, this is done by dividing the entire equation by the value of current.
This will cancel out current from the right side and divide the value of charge on the left side of the equation. This should look like
∆Q = ∆T

50C / 10A = 5 seconds

I x T /1.6x10^-19 = electrons passing a point per value of time

10 x 5 / 1.6 x 10 ^ -19 = 3.125 x 10^20


  1. I remember learning this in high school physics. good job sir

  2. ...I instantly regret my interest in electrical engineering.

  3. This brings me back to my school days.

  4. interesting but over my head lol

  5. Cool stuff, always trying to get a bit smarter :D

  6. everything you do in this blog lines up exactly with my physics class... are you in my physics class?

  7. I did not follow because you're basically speaking another language. But thanks for sharing anyways!

  8. oh boy, intro electricity in physics 2 brings back memories of how enjoyable solving all the electromagnetism problems was :p

  9. Now I feel stupid :( Thank you!

  10. Straight in my bookmarks under "revision" :D

  11. This was hard in college, and it's still hard today xD

  12. I think I followed all that.....

  13. Ugh how i hated physics, more specifically math.

  14. This all seems, correct, useful stuff :)

  15. I have no idea what you're talking about.

  16. electricity is gonna be the reason i fail phys II

  17. Loving it. Every word brings me closer to insanity!