Consider a solenoid of length l, radius r, and n turns. a. (two marks) Find the
ID: 1442512 • Letter: C
Question
Consider a solenoid of length l, radius r, and n turns.
a. (two marks) Find the self-inductance, L, of this solenoid.
b. (two marks) If two identical versions of this solenoid are connected end-to-end, by what factor is L increased? Explain why this is the case.
c. (two marks) Assume that the second solenoid has infinitesimally larger radius, and is placed around the first solenoid (i.e., they are placed on top of each other). They are connected so that the current flows in the same direction. By what factor is L increased? Explain why this is the case.
Explanation / Answer
part a )
L = uo*n^2*A
A = pir^2
L = uo*n^2*(pi*r^2)
part b )
connected end to end means they are going to connect in series
L = L1 + L2
L = 2L
100%
part c )
they are now connected in parallel
1/L = 1/L1+1/L2
L2 has infinitesimally larger radius = L2 = infinite
1/L2 = 0
L = L1 = L
does not change