Question

The positive terminal of $12\,{\text{V}}$ battery is connected to the ground. Then the negative terminal will be at:
A.$- 6\,{\text{V}}$
B.$+ 12\,{\text{V}}$
C. Zero
D.$- 12\,{\text{V}}$

Answer 1

First explain the mean of the battery of $12\,{\text{V}}$ in terms of the potential difference between the positive and negative terminals of the battery. Also explain the meaning of ground in a circuit and the potential of the ground in a circuit. Then using the law of conservation of energy, determine the potential of the negative terminal of the battery when the positive terminal is connected to ground.

Complete step by step answer:
We have given that the positive terminal of a $12\,{\text{V}}$ battery is connected to the ground. We have asked to determine the potential at the negative terminal of the battery.We know that the battery of $12\,{\text{V}}$ means that the potential difference across the two positive and negative terminals of the battery is $12\,{\text{V}}$.
${V_ + } - {V_ - } = 12\,{\text{V}}$
Here, ${V_ + }$ is the potential of the positive terminal of the battery and ${V_ - }$ is the negative terminal of the battery.

We have given that the positive terminal of the battery is connected to the ground.The ground in a circuit refers to a reference terminal with zero voltage.Hence, when the positive terminal of the battery is connected to the ground with zero potential, there is flow of charges from the positive terminal of the battery to the ground at zero potential. This flow of charges occurs until the potential of the positive terminal of the battery becomes zero.

But according to the law of conservation of energy, the potential difference between the two terminals of the battery should be the same all the time.To maintain this potential difference constant, the potential of the negative terminal of the battery becomes $- 12\,{\text{V}}$.Therefore, the negative terminal will be at $- 12\,{\text{V}}$.

Hence, the correct option is D.

Note: The students may assume that when the positive terminal of the battery is connected to the ground, there is flow of charges from the terminal to the ground until the potential of the positive terminal becomes zero means that the battery provides the charges to the ground. But the students should keep in mind that the battery only provides potential for the free electrons in the conductor to flow and not the charges.