If you must do positive work to bring a charged balloon toward a negatively charged sphere, is the charge on the balloon positive or negative? Or can it have any sign?

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Physics

15 November, 17:08

If you must do positive work to bring a charged balloon toward a negatively charged sphere, is the charge on the balloon positive or negative? Or can it have any sign?

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Tobias Smith · Answer 1

Let's start from the definition of attraction and repulsion. Similar charges tend to repel each other, while different charges attract. When work is done due to the force of attraction its value will be negative, while if work is done due to the force of repulsion its value will be positive.

Given this the sphere has a negative charge.

In other words, if the balloon has a positive charge, it will be attracted by the sphere with negative charge. In this case, you would not have to do a positive job to bring them together. If the balloon has a negative charge, it will be repelled by the sphere with a negative charge. In this case, you will do a positive job to unite them.

Therefore, the load on the balloon is negative.