Finding a resistance is very easy all you have to do is only putting a particular type of resistors into it.
What is resistance of the any given material?
Resistance is the ability to stop down the flow of current through them.
Which Theory used to find the resistance?
Wheatstone bridge is used to find the resistance.
What is Wheatstone bridge?
A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. One of the Wheatstone bridge’s initial uses was for the purpose of soils analysis and comparison.
Aim: To find out the resistance for a carbon resistor.
Theory: The ratio of the 1st combination of resistor is equal to the ratio of 2nd combination of resistor. (You will understand it later on when you will see the below diagram.)
First, Kirchhoff’s first rule is used to find the currents in junctions B and D:
Then, Kirchhoff’s second rule is used for finding the voltage in the loops ABD and BCD:
When the bridge is balanced, then IG = 0, so the second set of equations can be rewritten as:
Then, the equations are divided and rearranged, giving:
From the first rule, I3 = Ix and I1 = I2. The desired value of Rx is now known to be given as:
If all four resistor values and the supply voltage (VS) are known, and the resistance of the galvanometer is high enough that IG is negligible, the voltage across the bridge (VG) can be found by working out the voltage from each potential divider and subtracting one from the other. The equation for this is:
where VG is the voltage of node B relative to node D.
Scale, iron element wire, Few combination of resistor, connecting wire, Voltmeter (I use multimeter).
1. Take a scale (I use stainless steel scale).
2. Wrap it with tape so that it could not conduct.
3. Now take iron element
4. Tie it as shown in figure.
5. Connect the wires and resistor in the scale.
6. Connect the multi meter according to circuit given above.
7. Connect the battery’s wire in the scale’s wire. Positive to one end and negative to second end.
8. Set the multimeter till the milivoltage becomes zero or almost zero.
9. Take the reading of the scale.
10. The positive wire should be connected to the known resistor. And negative should be with unknown resistor. You can also see in the circuit.
11. The length of wire between the positive and the multimeter wire is R1. And the length of the wire between the negative and the galvanometer wire is R2.
12. Now last step to be done and find the resistance of the unknown resistance.
13. My multimeter reading goes till 0.6v and then I read that the R1 is 10 and R2 is rest 20.
14. Now calculate it.
The resistance of the unknown resistor is 36 Ohm.
1. This is the safest method or you can say easier method to work in this.
2. Can find very small resistance and can also find very high resistance by changing the value of current.
3. Does not require any heavy metals.
4. Very eco friendly.
5. No pollution.
1. This gives you precise value you cannot use it that appliances which will give requires exact amount of resistor.
2. If the wire is not connected properly from anywhere you will get the value properly.
3. Any mistake can lead to a high injure to health.
4. Always wear insulator while working with high voltage to find the high resistance. If forgot can lead to the electric shock.
New user always find the value wrong so first find the known resistance and when you will feel that now you find the value than you can find the value of unknown resistance.
So work hard and when you are used to it you will feel very easy to do it so.
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Filed Under: Electronic Projects