Voltage Null Points of a Mechanical Meter Bridge

• Shreya
In summary, the resistance of the wire plays a crucial role in determining the potential drop and current flow in a circuit. Moving the jockey to the left decreases the resistance of AD, resulting in a higher potential at point D and causing a current to flow from D to B. Despite this reasoning, the textbook claims that there is no current flowing from D to B when the jockey is connected to the left of D. This contradicts the earlier explanation and requires further clarification.

Shreya

Homework Statement
The answers of this question is mentioned to be A & C. My question is why isn't B true?
Relevant Equations
-
My reasoning is that the wire has a resistance/unit length. The resistance of AD must equal that of AB for D to be called a null point. If we move jockey to the left, the resistance of AD decreases, thereby decreasing the potential drop across it. This means that the V of D is more than that of B causing a current to flow from D to B. So according to me B should be an answer, while the textbook says.

Attachments

• SmartSelect_20220220-150850_Drive.jpg
31.9 KB · Views: 59
Last edited:
when jockey is connect to the left of D no current in the wire B. that is why its wrong

Shreya
salmanshu322 said:
when jockey is connect to the left of D no current in the wire B. that is why its wrong
I cannot understand why it is so. Could you please explain? According to my reasoning the resistance of AD< that of AB. Therefore, the V drop across AD is lower making D at a higher potential than B, causing a current to flow from D to B.

1. What is a voltage null point?

A voltage null point is a point on a mechanical meter bridge where the voltage between two points is zero. This can be achieved by adjusting the position of a galvanometer or by using a Wheatstone bridge circuit.

2. How is a voltage null point determined on a mechanical meter bridge?

A voltage null point is determined by adjusting the position of a galvanometer until the needle reads zero. This indicates that the voltage between the two points on the meter bridge is balanced and there is no potential difference.

3. What is the significance of a voltage null point in a mechanical meter bridge?

The significance of a voltage null point is that it allows for accurate measurement of unknown resistances. By balancing the voltage, the resistance of the unknown component can be calculated using the known resistances on the meter bridge.

4. Can a mechanical meter bridge be used to measure AC voltages?

No, a mechanical meter bridge is only capable of measuring DC voltages. This is because the galvanometer used in the meter bridge is designed to measure current in one direction only.

5. What are some common sources of error when using a mechanical meter bridge?

Common sources of error when using a mechanical meter bridge include parallax error, which occurs when the observer's eye is not directly in line with the needle on the galvanometer, and resistance in the connecting wires, which can affect the accuracy of the measurements.