A 500 turn solenoid with a length of 20 cm and a radius of 1.5 cm carries a current of 2.0 A. A second coil of four turns is wrapped tightly about this solenoid so that it can be considered to have the same radius as the solenoid. Find the following when the current in the solenoid increases to 5.0 A in a period of 0.90 s.

Question

A 500 turn solenoid with a length of 20 cm and a radius of 1.5 cm carries a current of 2.0 A. A second coil of four turns is wrapped tightly about this solenoid so that it can be considered to have the same radius as the solenoid. Find the following when the current in the solenoid increases to 5.0 A in a period of 0.90 s. 
(a) the change in the magnetic flux through the coil 
T·m2 
(b) the magnitude of the average induced emf in the coil 
V

bobpursley · Answer

I need to see your thinking. These are very basic questions about computing magnetic flux from current in a solenoid, and from the changing B calculating the emf generated using faradays law. I need to see what you are missing.