Answer:

Explanation:
Given that
Radius =r
Electric filed =E
Q=Charge on the ring
The electric filed at distance x given as

For maximum condition



For maximum condition




At
the electric field will be maximum.
Answer:
Frictional force increases with the increase in the roughness of the surface.
Explanation:
You will see that the rougher the surface, the greater the wear and tear.
Your answer is B.
The relationship between medium temperature and speed of sound is a direct relationship: when one factor increases, the other increases as is shown in graph B. The British would choose the the time of day which would give the lowest speed of sound, because this would be easiest to break. Graph B shows that the lowest speed of sound would occur with the lowest air temperature - in the morning.