Resistors

Resistor is the fundamental part of the circuit,let us now move on to it and its correctness. Starting with its fundamentals.
So,What is a Resistor?.
Resistor is the one, that resists the flow of current in the circuit. So,by noticing its property we can easily comeup with the conclusion that we can use it for regulating the flow of current in the circuit. It works on the principle of "ohm's law". According to the law "Flow of charges per unit time in the circuit is directly proportional to the potential difference in the circuit", which means that ratio of potential difference between the ends of the conductor that conducts currents is a constant that varies on the basis of current and potential difference and that constant is called resistance.

V/I=constant =resistance(R)
Resistance is measured in ohms.
Resistance is said to be 1ohm if 1 Ampere of current flows in the circuit with the potential difference of 1volt.
1ohm=1V/1A

Electronic Symbol is:
So,to understand more about resistance let us brush up little bit about Current and Electric potential.
So, what is Current?
Current is the flow of charges per unit time.
I=q/t
q --->Charge
t---->Time
I---->Current
Which is measured in Ampere.

What is Electric potential between to points? It is work done to bring unit charge between two points. V=q/w q---->Charge w---->Work Which is measured in Volts.
Before that it is an essential step for us to find the colour code which is in turn a direct or indirect step to compute the Resistor value.

So,what is colour code?
Colour code is the one which indicates rating of electronic component(Resistor).This colour codes is the method of representation,which was developed in 1920s by a Radio Manufacturers Association which got highly popularized as it made the Electronic gauges economically feasible by comman man.

The significance attached to difficult colours is given in the following table:

Steps involved in determining Resistance using colour code:

1. The colour of 1st ring in the extreme left of the resistor gives the 1st digit from the left of the resistance value of that resistor.
2. The colour of 2nd ring in the extreme left of the resistor gives the 2nd digit from the left of the resistance value of that resistor.
3. The colour of 3rd ring gives the 10th power by which first two digit must be multiplied.
4. The colour of 4th ring gives the tolerance of the resistor.

Calculation:
First Band Red.............2
Second Band Violet......7
Multiplier Band Green...100kohm
Tolerance Band Gold.....±5%
Equation:
27 x 100,000 = 2700,000
1,000 = 1K
Resistor = 2700 Kohm
with a ±5% Tolerance.

Now having known the value of resistance which was determined by the method of colour code,let us come to know i ts correctness using multimeter.

So the steps involved for doing this are:

1. Detach the resistor from the circuit whose correctness has to be determined.
2. Set the Multimeter to ohmic range with the knobe directing towards the value of the resistor obtained using color code without considering the tolerance.
3. Power off the circuit containing the resistor you wish to measure. Never measure a resistor in a circuit with a live current running through it.
4. Attach the wire which is attached to either end of the resistor to the +ve and -ve poles of the Multimeter,but it doesnt make any difference as any leg of the resistor can be attached to any pole as there is no polarity due to its detachment from the circuit.
5. Note the value that we get from the Multimeter and compare it with the value that you first obtained using colour code.
6. If the noted value is infinity or exceeds the first value then the resistor has to be replaced by the resistor with the required value.

Tips & Warning:
Failing to remove power from the circuit or discharge capacitors could result in damage to your multimeter in addition to misleading measurements.

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