Voltage Null Points of a Mechanical Meter Bridge

[Shreya]

Homework Statement

The answers of this question is mentioned to be A & C. My question is why isn't B true?
Please be kind to help

Relevant Equations

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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.

 

[salmanshu322]

when jockey is connect to the left of D no current in the wire B. that is why its wrong

 

[Shreya]

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.