Thursday, February 11, 2010
Electric current is the flow of electricity from one point in a circuit to another. The current is a measure of the flow or quantity of electrons that pass a given point in one second. Most people use the "Ampere" as their unit of electric current flow. When one ampere of current is flowing in a wire, 6,280,000,000,000,000,000 electrons per second are flowing. By the way, this number of electrons is also given a name. It's called a "coulomb". The coulomb is a quantity of charge, the ampere is a measure of flow. You have one ampere when one coulomb of electrons flow per second. About 1 ampere flows through a 100 watt lamp when plugged into a 110 volt source.
Voltage is commonly used as a short name for electrical potential difference. Its corresponding SI unit is the volt (symbol: V).
Ohm's Law
To make a current flow through a resistance there must be a voltage across that resistance. Ohm's Law shows the relationship between the voltage (V), current (I) and resistance (R). It can be written in three ways: | where: | V = voltage in volts (V)
I = current in amps (A)
R = resistance in ohms ( ) | or: | V = voltage in volts (V)
I = current in milliamps (mA)
R = resistance in kilohms (k) |
For most electronic circuits the amp is too large and the ohm is too small, so we often measure current in milliamps (mA) and resistance in kilohms (k
). 1 mA = 0.001 A and 1 k
= 1000
.
The Ohm's Law equations work if you use V, A and , or if you use V, mA and k. You must not mix these sets of units in the equations so you may need to convert between mA and A or k and .
http://www.exploratorium.edu/xref/phenomena/electric_current.html
http://en.wikipedia.org/wiki/Voltage
http://www.kpsec.freeuk.com/ohmslaw.htm
your name @ 1:48 PM | your comment link
To make a current flow through a resistance there must be a voltage across that resistance. Ohm's Law shows the relationship between the voltage (V), current (I) and resistance (R). It can be written in three ways: