Question

When a soap bubble is charged ?

• A. Its radius increases
• B. Its radius decreases
• C. The radius remains the same
• D. Its radius may increase or decrease

Answer 1

The Correct Option is A

When a soap bubble is charged, the charges on the surface of the bubble repel each other, resulting in an increase in the radius of the bubble. This is due to the electrostatic repulsion between like charges. Since the charges try to spread out as much as possible, the bubble expands. Thus, when a soap bubble is charged, its radius increases.

So, the correct answer is (A): Its radius increases.

Answer 2

When a soap bubble is charged, the charges distribute themselves uniformly on the surface of the bubble. According to electrostatic principles, like charges repel each other. The repulsion between these charges creates an outward force, which increases the pressure inside the bubble. For a soap bubble, the internal pressure \( P_{\text{inside}} \) is greater than the external pressure \( P_{\text{outside}} \), and the difference in pressure is related to the surface tension \( \sigma \) and the radius \( r \) by the equation: \[ \Delta P = \frac{4\sigma}{r} \] When a charge is added to the soap bubble, the electrostatic repulsion between the charges leads to an increase in the internal pressure. To balance the increased internal pressure, the radius of the soap bubble must increase. Therefore, when a soap bubble is charged, its radius increases.