Question

A girl brings a positively charged rod near a thin neutral stream of water flowing from a tap. She observes, that the water stream, bends towards her. Instead, if she is to bring a negativity charged rod near to the stream, it will :

• A. bend in the same direction
• B. bend in the opposite direction
• C. not bend at all
• D. bend in the opposite direction above and below the rod

Answer 1

Answer: (A)

bend in the same direction

Water is dipolar in nature. Hence when water enters an electric field, the molecules rearrange themselves.

The case 1 in the figure, where a positively charged rod is brought near the water,

the negative charge moves towards the rod and positive charge moves away from the rod.

Hence, the attractive force is greater than the repulsive force and as a result, the water stream bends towards the rod.

To the contrast, in case 2, when a negatively charged rod is brought near the water, the molecules rearrange such that positive charge moves towards the rod and the negative charge moves away from it as shown in the figure.

In this case also, the attractive forces dominate the repulsive forces, and hence, the stream still bends towards the rod.