1.

When 100 V dc is applied a coil, a current of 1 Aflows through it. When 100 V 50 Hz ac is applied to the same coil, only 0.5 A flows. The indcutance of the coil is

Answer»

5.5 MH
0.55 mH
55 mH
0.55 H

Solution :R=` V/I = (100 V)/(1 A) = 100 Omega `
` Z = (V_(rms))/( 1_(rms)) =(100 V)/(0.5 A )= 200 Omega `
` As R^(2) + X_(L)^(2)= Z^(2)`
` X_(L)= sqrt(Z^(2) -R^(2)) = sqrt( 200^(2) - 100^(2)) = 100sqrt3 Omega `
As `X_(L) = OmegaL = 2 pi xx 50 xx L `
` L = ( X_(L))/(100 pi) = (100 sqrt(3))/(100 pi)= 0.55 H`


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