In an RL series circuit connected to a dc source and a switch, ...

[lidoalex]

In an RL series circuit connected to a dc source and a switch, the inductor gets 40 of its maximum current 1.8 s after the switch is closed at t = 0 s. What is the time constant of this circuit?
 
  A) 0.80 s
  B) 1.5 s
  C) 2.5 s
  D) 3.5 s
  E) 5.5 s

Question 2

According to general relativity, a photon emitted by a star
 
  A) loses energy.
  B) reduces in frequency.
  C) is red-shifted.
  D) all of the above
  E) none of the above

[lkoler]

Answer to Question 1

D

Answer to Question 2

Answer: D