Identifying Resistor Values

09/03/2011

Today i had six different types of resistors, i then looked at the colours on the resistors and matched them up with the numbers on the work sheet that was given to us.
e.g. brown = 1, red =2

One of my resistors was colour coded. Br, B, R and then a gold band at the end.

Br = 1
B = 0
R = 2
Gold = tolerance (5%)

Below is a picture of a 1k ohms resistor:

The first colour was brown so i put a 1 down because thats what it equals on the chart.
The second colour was 0 so i wrote it down next to the 1.
The third colour tells you how many zeros to put down, mine was red which means i put down 2 zeros.

i now have the answer 1000, because i was measuring resistance my answer is 1000 ohms

the gold band is the tolerance of how much my resistor is allowed to be out by, mine was 5%. i then measured my resistor with a multimeter and i was within specification reading 1000 ohms


i was then asked to choose to resistors measure their individual ohm resistance with a multimeter.
Resistor 1 =  98.7ohms, Resistor 2 = 27ohms

Once i did that i had to join them together in series by joining one end of each together, then calculate and measure the combined value.

for the calculated value i just added the two seperate resistances together because in a series circuit the total resistance is the individual resistors added together. Calculated = 125.7ohms
When i did the measured resistance i put the prongs of my multimeter on each end of the joined resistors  and set my multimeter to ohms and measured the resistance. Measured = 125.3

This is easy to remember and is a fast was to find out if your resistors are in spec

When i had finished that, i was asked to join the resistors together in parallel by joining both ends of the resistors together so one was on top of the other. I then had to calculate the total resistance.

For the calculated value i used the formula:

1/Rt = R1xR2 / R1+R2

      = 98.7x27 / 28.7+27

       = 2664.9 / 125.7

       = 21.2 ohms

The total resistance must always be lower than the resistance of the lowest resistor.

I then put the prongs of the multimeter on each end of the resistors and set the multimeter to ohms and measured the resistance. my answer was = 21.4ohms

i find that this equation is good for working out because i can now tell that my resistors are within specifications.



Reference:

i got my link of resistor from: www.thebestcasescenario.com

i got my colour chart from: thebestcasescenario.com