so it is not true that voltmetre polarity should

The polarity of a voltmeter does not always need to match the polarity of the cells being measured, but it is important to understand the implications of doing so.

Understanding Voltmeter Polarity

A voltmeter is designed to measure the voltage difference between two points. When connecting a voltmeter to a circuit, the positive lead should ideally connect to the more positive point, and the negative lead to the more negative point.

What Happens If Polarity Is Reversed?

• If the leads are reversed, the voltmeter will still measure the voltage, but it will display a negative value.
• This negative reading indicates that the leads are connected in the opposite direction from what is expected.

Practical Considerations

In practice, while it is best to match the voltmeter's polarity to the cell's polarity for clarity, it is not a strict requirement. The key is to interpret the readings correctly based on how the leads are connected.

Key Takeaway

Always aim to connect the voltmeter correctly for accurate readings, but remember that reversing the leads will simply result in a negative voltage reading without damaging the device.