InterviewSolution
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InterviewSolution
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State the principle of working of a transformer. (b) Define efficiency of a transformer. (c ) State any two factors that reduce the efficiency of a transformer. (d) Calculate the current drawn by the primary of a `90%` efficient transformer which steps down 220 V to 22 V , if the output resistance is 440 `Omega`. |
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Answer» (a) Principle : It works on the principle of mutual induction. (b) Definition of efficiency : It is ratio of output power to input power. `n=("Output power")/("Input power")=(V_(s)I_(s))/(V_(p)I_(p))` (c ) Two factors which reduce the efficiency of transformer : (i) Magnetic flux leakage (ii) Eddy current (iii) Magnetic hysteresis / Resistance of winding (d) `V_(s)=22V,n=90%=0.90,R_(0)=440Omega, V_(s)=I_(s)R_(0)` `I_(s)=(V_(s))/(R_(0))=(22)/(440)=(1)/(20)A=(V_(s)I_(s))/(V_(p)I_(s))rArr0.90=(22xx(1)/(20))/(220xxI_(p))` `I_(p)=(22xx(1)/(20))/(220xx0.90)=(cancel(22))/(20)xx(1)/(cancel(220)_(10)xx0.9)=(1)/(200xx0.9)=(1)/(180.0)` `I_(p)=(1)/(180)A` |
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