Electrical Instruments

To solve this problem, let's understand the configuration of the voltmeters in the circuit provided:

1. We have three voltmeters, , , and , connected across points and in the given figure.
2. The key point to understand is how voltmeters work: they measure the potential difference between two points.
3. In the circuit shown, and are in parallel and essentially across the same two points (assuming ideal voltmeters for simplicity).
4. measures the total potential difference across and which includes both and .
5. This means the overall potential difference that measures is the sum of what and are measuring.
6. Thus, the correct relationship is: .

Now, let's verify why this option is correct and others are not:

• : This is incorrect since they can have different readings due to different internal resistances.
• : This statement is true due to our conclusion, but the option requires a strict inequality assertion.
• : This cannot be true, as per our principle, is the sum of .

Thus, the correct answer is: .

Tip: When dealing with voltmeters in series or parallel, always consider how they split or measure potential difference across points.