Previous Year Question
A coil having 1000 turns is wound on a core. The flow of 1 A current through the coil produces 1 mWb flux in the core. What will be the energy stored in the magnetic field?
Correct answer: A
Explanation
Flux linkage is λ=NΦ=1000×1 mWb=1 Wb-turn. For a linear magnetic system, stored energy is W=1/2 λI. With I=1 A, W=0.5 J, matching option A.
Formula
λ=NΦ=1 Wb-turn; W=1/2 λI=0.5J
Step-by-step solution
Correct Answer
A — 0.5 J
Concept and Reasoning
Flux linkage is λ=NΦ=1000×1 mWb=1 Wb-turn. For a linear magnetic system, stored energy is W=1/2 λI. With I=1 A, W=0.5 J, matching option A.
Calculation / Key Relation
λ=NΦ=1 Wb-turn
W=1/2 λI=0.5J
Exam Takeaway
For a linear magnetic system, field energy is one-half flux-linkage times current.
Common Mistake
Convert mWb to Wb before multiplying by turns.
Common mistake
Convert mWb to Wb before multiplying by turns.
Exam tip
For a linear magnetic system, field energy is one-half flux-linkage times current.
Quick method
For a linear magnetic system, field energy is one-half flux-linkage times current.