Answer: option B 
Explanation: when a neutral atom loses an electron or gains a positive charge electron, it becomes a positive ion (positively charged) and when an neutral atom gains an electronic charge or losses a positive charge electron, it becomes a negative ion (negatively charged). 
 
        
                    
             
        
        
        
Energy Density = 1/2 × ε(0) × (V/d)^2
V = 100, d = 0.01, ε(0) = 8.85 x 10^-12
        
             
        
        
        
Answer: B. meteorites, UV rays
The earth's atmosphere plays an important role in shielding the space rocks and meteorites enters inside the earth due to collision with the celestial body. Due to high heat and pressure in the mesospheric layer of the atmosphere these meteorites burned up before reaching the biosphere or hydrosphere system of the earth. The UV rays are protected from entering into the earth atmosphere by the ozone layer present in the stratosphere of the atmosphere. Both meteorites and UV rays can negatively effect the human population. Therefore, the atmosphere is an agent which provides protection against them. 
 
        
                    
             
        
        
        
Answer:
1.27 m
Explanation:
Distance = 192 m 
number of rotations = 48 
Distance traveled in one rotation = 2 x π x r 
Where, r be the radius of wheel.
so, distance traveled in 48 rotations = 48 x 2 x 3.14 x r 
It is equal to the distance traveled. 
192 = 48 x 2 x 3.14 x r 
r = 0.637 m 
diameter of wheel = 2 x radius of wheel = 2 x 0.637 = 1.27 m
 
        
                    
             
        
        
        
Answer:
amount of charge on the source charge