Answer:
Here is the complete question:
https://www.chegg.com/homework-help/questions-and-answers/magnetic-field-372-t-achieved-mit-francis-bitter-national-magnetic-laboratory-find-current-q900632
a) Current for long straight wire 
b) Current at the center of the circular coil 
c) Current near the center of a solenoid 
Explanation:
⇒ Magnetic Field due to long straight wire is given by (B),where

Plugging the values,
Conversion
,and 

⇒Magnetic Field at the center due to circular coil (at center) is given by,
So 
⇒Magnetic field due to the long solenoid,
Then
So the value of current are
,
and
respectively.
I'd go for D here. It also fits in with the idea of thermal expansion - as something is heated up, molecules vibrate and maybe collide. they vibrate with bigger amplitudes, so taking up more space, so expanding. maybe
It is number 3 because I know it is
Answer: W = 11340J
Explanation:
Hey there! I will give the following steps, if you have any questions feel free to ask me in the comments below.
So this is the Formula: Power = Work / Time.
<u>Step 1:</u><em><u> Find the Formula</u></em>
P = W / T
<em><u>
</u></em>
<u>Step 2: </u><u><em>Make W the subject of the equation.</em></u>
W = PT
<u>Step 3:</u><u> </u><u><em>Given.</em></u>
P = 270 Watts, T = 42 seconds
<u>Step 4:</u><u><em> Substitute these values into equation 2
.</em></u>
W = 270(42)
<u>Step 5:</u><u> </u><u><em>Simplify.</em></u>
W = 11340J
The amount of work done was 11340.
~I hope I helped you! :)~
The change in potential energy of an object is given by

where
m is the mass of the object
g is the gravitational acceleration

is the increase in altitude of the object
In our problem,

is the mass of the book,

and

is the increase in altitude of the book, so its variation of potential energy is