Comment on What is negative voltage?

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yetAnotherUser@discuss.tchncs.de ⁨1⁩ ⁨week⁩ ago

If you (or anyone else) wants to check their understanding of voltage as the difference between two electric potentials, here’s a couple exercises I stole from a text book:

(Note: Electric potential is also measured in Volt.)

A battery has a constant voltage of 1.5V between its plus and its minus pole. What is the electric potential of the minus pole compared to ground potential when:

  1. The battery is on an electrically isolating mat?
Solution

The battery is not connected to ground. Therefore, no statements about the electric potential of either pole can be made.

  1. The minus pole is connected to ground?
Solution

Because of the connection, the electric potential of the minus pole equals that of the ground, which is by definition 0V.

  1. The plus pole is connected to ground?
Solution

Now the potential of the plus pole equals that of the ground. We know that the voltage difference between the plus and minus pole is 1.5V. Since this difference is measured by subtracting the potential of the minus pole from the potential of the plus pole the equation: 1.5V = p_plus - p_minus = 0V - p_minus => p_minus = -1.5V. Therefore the potential of the minus pole is -1.5V.

  1. The plus pole is connected to a generator producing an electric potential of 10,000V compared to ground?
Solution

Now the electric potential of the plus pole is also 10,000V. The potential of the minus pole must be 1.5V lower, so it must equal 9998.5V.

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