Electro Magnetic Induction And Alternating Currents Question 599
Question: Two identical induction coils each of inductance L joined in series are placed very close to each other such that the winding direction of one is exactly opposite to that of the other, what is the net inductance [DCE 2003]
Options:
A) L2
B) 2L
C) L/2
D) Zero
Show Answer
Answer:
Correct Answer: D
Solution:
When the two coils are joined in series such that the winding of one is opposite to the other, then the emf produced in first coil is 180o out of phase of the emf produced in second coil. Thus, emf produced in first coil is negative and the emf produced in second coil is positive so, net inductance is $ L=L_{1}+L_{2}=L+L $
$ \Rightarrow L=-\frac{\varphi }{i}+\frac{\varphi }{i}=0 $
