The red wire on a voltmeter is the cathode and the black is the anode. This would also give a positive reading on the voltmeter.
How would I explain why this is?
I'm sorry, but the information you've provided seems to be incorrect. In most cases, the red wire is typically used as a positive connection, while the black wire is used as a negative or ground connection. The terms "cathode" and "anode" are commonly used in reference to electronic components such as diodes and batteries, where the flow of current is controlled.
To explain why a positive reading on a voltmeter may be observed when connecting the red wire as positive and the black wire as negative, we need to understand the concept of voltage measurements. A voltmeter is designed to measure the potential difference between two points in an electrical circuit. It does this by connecting the red wire to the point with higher potential (positive terminal) and the black wire to the point with lower potential (negative terminal).
When the red wire is connected to the positive terminal and the black wire is connected to the negative terminal, the voltmeter displays a positive reading. This is because the potential difference between these two points creates an electric field or a potential gradient, and the voltmeter measures the strength of this gradient.
It's important to note that the actual color-coding of wires can vary depending on the device or system you're working with. To be certain about wire polarity and avoid confusion, it's advisable to consult the manufacturer's instructions or documentation.