a is the answer..... ( just an FYI no black dwarfs actually exist yet)
<span>The speed of ray of light traveling through a substance whose index of refraction 1.1 is
(c/1.1) = (299,792,458 m/s) / 1.1 = </span>272,538,598 m/s
These are the correct answers. I couldn't get the rest of the answers
Answer:
The number of turns in the solenoid is 230.
Explanation:
Given that,
Rate of change of current, 
Induced emf, 
Current, I = 1.5 A
Magnetic flux, 
The induced emf through the solenoid is given by :

or
........(1)
The self inductance of the solenoid is given by :
.........(2)
From equation (1) and (2) we get :

N is the number of turns in the solenoid


N = 229.28 turns
or
N = 230 turns
So, the number of turns in the solenoid is 230. Hence, this is the required solution.
Torque [Nm] = Force [N] x Force arm [m]
C=F*b=20*0.20=4 Nm
The correct answer is C