# Very basic circuit question about a Wheatstone Bridge

• User1265
In summary, two resistors are in series if both their ends are at the same electric potential, and they are parallel if one end is at a different electric potential from the other end.
User1265
Homework Statement
My Question is how would find the current of the ammeter

Image inserted in solution
The answer says "balanced wheatstone bridge, I = 0" I do not quite understand.
Relevant Equations
V=IR
I tried to solve by making 4 ohm and 8 ohm, which I believe are parallel as one effective resistance, and making 6 and 12 ohms which I believe are parallel as one effective resistance, and diving the total of the two effective resistance by the total voltage, but by doing so, I can only find the total current in the circuit, whereas I need the current in the branch containing the ammeter.

However the answer noted it was a 'balanced wheatstone bridge'. What does this mean? and what are the implications of this upon solving to find the current in the Ammeter?

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User1265 said:
However the answer noted it was a 'balanced wheatstone bridge'. What does this mean? and what are the implications of this upon solving to find the current in the Ammeter?
Look it up here.

User1265 said:
which I believe are parallel
question your belief: only one of the two ends of both is in common

BvU said:
question your belief: only one of the two ends of both is in common
Could you elaborate more on how you identify in this particular case which are in parallel and which are in series and why this is in this case?

Two resistors are in series if all the current that goes through one resistor has to go through the other before encountering a node where more than two circuit elements are connected.

Two resistors are in series if both their ends are at the same electric potential, i.e. the voltage across them is the same.

Note that the ammeter in the diagram is assumed to be ideal, i.e. it has zero resistance, the voltage across it is zero, and doesn't count as a circuit element. Also note that if two resistors are not in series, this does not necessarily mean that they must be in parallel. They can be neither in series nor in parallel.

User1265
kuruman said:
ammeter in the diagram is assumed to be ideal, i.e. it has zero resistance, the voltage across it is zero, and doesn't count as a circuit element.
Does this mean no current would be flowing through that part?

No. The straight wires connecting the resistors are also considered to have zero resistance, yet current flows them. On the contrary, ammeters measure all the current in whatever part of the circuit they are connected.

A bit of a typo, methinks.

kuruman said:
Two resistors are in series?? parallel ?? if both their ends are at the same electric potential, i.e. the voltage across them is the same.
https://www.electronics-tutorials.ws/resistor/res_4.html

https://www.electronics-tutorials.ws/resistor/res_3.html

## What is a Wheatstone Bridge?

A Wheatstone Bridge is a simple electrical circuit that is used to measure unknown resistance values. It consists of four resistors arranged in a diamond shape with a power source and a galvanometer (a sensitive current measuring device) connected in between the two arms of the diamond.

## How does a Wheatstone Bridge work?

A Wheatstone Bridge works by using the principle of balancing two opposing circuits. When the two arms of the diamond have equal resistance, no current will flow through the galvanometer and it will read zero. This allows for the unknown resistance to be calculated using the known resistances and the ratio of the resistances in the two arms of the bridge.

## What is the purpose of a Wheatstone Bridge?

The main purpose of a Wheatstone Bridge is to measure unknown resistance values accurately. It is commonly used in applications such as strain gauges, temperature sensors, and in the calibration of other electrical equipment.

## What are the advantages of using a Wheatstone Bridge?

One of the main advantages of using a Wheatstone Bridge is its high accuracy. It is also a simple and cost-effective circuit, making it a popular choice in many industries. Additionally, it can be used to measure a wide range of resistance values.

## Are there any limitations to using a Wheatstone Bridge?

While a Wheatstone Bridge is a useful circuit, it does have some limitations. It requires a power source and a galvanometer, which can add to the complexity and cost. It is also sensitive to changes in temperature and can be affected by external factors such as electromagnetic interference.

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