If the needle of a DC voltmeter moves backwards when connections are changed, what does this indicate?

If the needle of a DC voltmeter moves backwards when connections are changed, it indicates that the meter leads are reversed. This behavior is a typical response of a DC voltmeter when the positive lead is connected to a lower voltage point than the negative lead. Essentially, the voltmeter measures the potential difference between the two terminals, and reversing the connections causes the meter to register a negative voltage, which is reflected by the needle moving in the opposite direction.

While the other options suggest potential issues, they do not apply in this scenario. A damaged meter would likely produce erratic readings or not function at all, while a voltage that is too high would not cause the needle to move backward, but rather could damage the meter. An open circuit would result in no reading at all, rather than a backward movement of the needle. Therefore, the observation of the needle moving backwards when the connections are reversed directly confirms that the leads are indeed switched.