STARTING WITH BEN FRANKLIN
Friday, March 5, 2010Potential Difference (Voltage)
Imagine that in you decided to spend your next week-end in himalaya mountains (it's very cold there ,is't it ? ) with your friends and an Avalanche is occurred (ohhh action film) , have you asked your self why this ball of ice take its way to the earth , of course it have a potential energy resulted from height due to gravitational force .
What is the Microcontroller ?
A CURRENT BEGAN
Thursday, March 4, 2010
Useful Quantities
Resistance And Resistor (Part # One)
Wednesday, March 3, 2010
An examples For More Understanding ohm's law
Resistance And Resistor (Part # Two: Let's start to buy our first component)
Resistor values - the resistor colour
code
1
Ω
is quite small so resistor values are often given in kΩ
and MΩ
(why..?).1 k
Ω
= 1000Ω
, 1 MΩ
= 1000000Ω
.Resistor values are normally shown using coloured bands.
Each colour represents a number as shown in the table.
Most resistors have 4 bands:
- The first band gives the first digit.
- The second band gives the second digit.
- The third band indicates the number of zeros.
- The fourth band is used to shows the tolerance (precision) of the resistor, this may be ignored for almost all circuits but further details are given below.
This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.
So its value is 270000 Ω = 270 kΩ.
On circuit diagrams the
Ω is usually omitted and the value is written 270K.
Find out how to make your own Resistor Colour Code Calculator
Small value resistors (less than 10 ohm)
The standard colour code cannot show values of less than 10. To show these small values two special colours are used for the third band: gold which means × 0.1 and silver which means × 0.01. The first and second bands represent the digits as normal.For example:
red, violet, gold bands represent 27 × 0.1 = 2.7Ω
green, blue, silver bands represent 56 × 0.01 = 0.56 Ω
Tolerance of resistors (fourth band of colour code)
The tolerance of a resistor is shown by the fourth band of the colour code. Tolerance is theprecision of the resistor and it is given as a percentage. For example a 390 resistor with a tolerance of ±10% will have a value within 10% of 390Ω, between 390 - 39 = 351Ω and 390 + 39 = 429Ω (39 is 10% of 390).A special colour code is used for the fourth band tolerance:
silver ±10%, gold ±5%, red ±2%, brown ±1%.
If no fourth band is shown the tolerance is ±20%.
Tolerance may be ignored for almost all circuits because precise resistor values are rarely required.