What happens to a voltmeter reading if the positive terminal is connected to the negative terminal of a source?

When a voltmeter is connected such that its positive terminal is connected to the negative terminal of a voltage source, it essentially reverses the expected polarity of the measurement. A voltmeter is designed to read the voltage across two points by indicating the potential difference with respect to the polarity of the connections.

In this case, connecting the positive lead of the voltmeter to the negative terminal means that the voltmeter will measure the voltage but will report it with the polarity inverted. This results in a reading that is often described as "backwards," as it indicates a negative value corresponding to the positive potential at the negative terminal being measured against the actual positive terminal of the voltage source.

Therefore, the correct interpretation is that the voltmeter will read backwards, reflecting the negative measurement against the typical polarity expected during a proper connection.