Effective reisistance of an unbalanced wheatstone bridge.

In summary, the person is requesting help with finding the resistance of an unbalanced wheatstone bridge for an exam. They provide the values for R1, R2, R3, R4, and R5, and mention that R1/R2 is not equal to R3/R4. They are unsure of how to solve this question and are seeking assistance. Another person suggests using KCL and the node voltage method, which would result in two equations with two unknowns. The person is then able to calculate the voltage and current, and ultimately the resistance. They thank the person for their explanation and assistance.
  • #1
Mr Virtual
218
4

Homework Statement



I have an exam and therefore quick help is requested.

I need a simple way to find out the resistance of an unbalanced wheatstone bridge.
Suppos R1=2 ohm, R2=1 ohm, R3=4 ohm, R4=4 ohm and the connecting bridge's R5=10 ohm.
Here, R1/R2 is not equal to R3/R4. Then How to find net resistance.


The Attempt at a Solution



I don't know and can't find any way to attempt such a question, though there must be many. So no idea how to do this.

Help please!


Mr V
 
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  • #2
Usually on problems like this one, you can use KCL to solve for the node voltages (assume 1V across the whole bridge for the calculation). Once you have the node voltages, those give you the currents, which gives you the total current for the 1V excitation, which gives you the resistance.
 
  • #3
A little more explanation?
 
  • #4
Mr Virtual said:
A little more explanation?

I agree with berkeman. Use the node voltage method, for the two nodes on either side of R5.

You'll have 2 equations, with two unknowns. Once you have the voltage of those two nodes, you can get the current coming out of the voltage source in terms of V.

Then resistance is just V/I.
 
  • #5
Thanks so much!
 

1. What is an unbalanced wheatstone bridge?

An unbalanced wheatstone bridge is an electrical circuit that is used to measure an unknown electrical resistance. It consists of four resistors arranged in a diamond shape with a voltage source and a galvanometer connected in between two opposite corners.

2. How do you calculate the effective resistance of an unbalanced wheatstone bridge?

The effective resistance of an unbalanced wheatstone bridge is calculated by taking the ratio of the voltage difference between two opposite corners of the bridge and the current flowing through the galvanometer. This is known as the bridge ratio and can be expressed as R = V/I.

3. What is the purpose of using an unbalanced wheatstone bridge?

The purpose of using an unbalanced wheatstone bridge is to measure an unknown electrical resistance with high accuracy. It is commonly used in scientific experiments and engineering applications to determine the resistance of various materials and components.

4. What factors can cause an unbalanced wheatstone bridge?

An unbalanced wheatstone bridge can be caused by a number of factors such as the resistance of the connecting wires, temperature changes, and variations in the voltage source. It can also be caused by human error in setting up the circuit or reading the measurements.

5. How can you improve the accuracy of an unbalanced wheatstone bridge?

To improve the accuracy of an unbalanced wheatstone bridge, it is important to minimize the effects of external factors such as temperature and resistance of the connecting wires. This can be achieved by using high-quality components, keeping the circuit at a constant temperature, and using precise instruments for measurements.

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