In the open circuit the current can not flow from one end of the power source to the other. Because of this there is no current flow, and therefore the light does not turn on.
Answer:

Explanation:
Given:
width of the wire, 
thickness of the flat wire, 
length of the wire, 
voltage across the wire, 
current through the wire, 
Now the net resistance of the wire:
using ohm's law



We have the relation between the resistivity and the resistance as:

where:
a = cross sectional area of the wire
resistivity of the wire material


Speed is constant. 50 miles = 1 hour. 600/50 = 12. 1hr(12) = 12 hours.
Explanation:
Equation for energy balance will be as follows.


Hence, 
Therefore, we will calculate the final temperature as follows.

= 868.03 R
Now, we will calculate the mass as follows.
m = 
= 
= 1.031 lbm
Hence,

Putting the values into the above equation as follows.


= 655.2 Btu
Thus, we can conclude that work done by paddle wheel is 655.2 Btu.
Mainly because of the higher energy of blue light than red light.
In fact, light is made of photons, each one carrying an energy equal to

where h is the Planck constant while f is the frequency of the light.
The frequency of red light is approximately 450 THz, while the frequency of blue light is about 650 Hz. Higher frequency means higher energy, so blue light is more energetic than red light and therefore it can cause more damages than red light.