Transformers only work with AC.
If you put DC into a transformer, all that comes out is smoke.
(a)
 
        
                    
             
        
        
        
Answer:
t₀ = 1.55 s
Explanation:
According to Einstein's Theory of Relativity, when an object moves with a speed comparable to speed of light, the time interval measured for the event, by an observer in  motion relative to the event is not the same as measured by an observer at rest.
It is given as:
t = t₀/[√(1 - v²/c²)]
where,
t = time measured by astronaut in motion = 3.1 s
t₀ = time required according to observer on earth = ?
v = relative velocity = 0.87 c
c = speed of light
3.1 s = t₀/[√(1 - 0.87²c²/c²)]
(3.1 s)(0.5) = t₀
<u>t₀ = 1.55 s</u>
 
        
             
        
        
        
Work done = Force X Distance 
3 430 000J = Force X 14m
Force = 3 430 000J / 14m
= 245 000 N
Hope this helps!
        
             
        
        
        
Answer:
A. The nucleus can be either positively charged or neutral.
Explanation:
The nucleus of an atom contains protons and neutrons only. Whereas electrons revolve around the nucleus. Protons are positively charged, neutrons have no charge and electrons are negatively charged.