Energy stored by a coil is doubled when its current is increased by percent.
A. 25
B. 50.14
C. 41.4
D. 100
Answer: Option C
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E=1/2(Li^2)
E*=1/2(L(sq(2).i)^2 (changed current i into Sqrt(2)i )
=2(1/2Li^2)
=2E
So to get double energy current has to be changed into sqrt(2)i
Change in current=Sqrt(2)i-i
=1.414-1=0.414=41.4%
Energy stored =1/2(L*i^2)
=>2E=2*(1/2(L*i^2))
=>2E=1/2(L*(sqrt(2)i^2))
Hence,
change in current =sqrt(2)i-i
=1.414-1
=0.414
therefore change in current = 41.4%
why????