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JIPMER 2009
Exam
JIPMER
Year
2009
Subject
Physics
Chapter
Alternating Current

JIPMER 2009 · Physics · Alternating Current

A transformer is used to light a 100 W and 110 V lamp from a 220 V...

A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A , the efficiency of the transformer is approximately

Options

  1. A30%30 \%
  2. B50%50 \%
  3. C90%90 \%
  4. D10%10 \%

Correct answer

C. 90%90 \%

Step-by-step solution

The efficiency of transformer = Energy obtained from the secondary coil  Energy given to the primary coil =\frac{\text{ Energy obtained from the secondary coil }}{\text{ Energy given to the primary coil }} or  or η= Output power  Input power  or η=VsIsVpIp Given, VsIs=100W,Vp=220V,Ip=0.5A Hence, η=100220×0.5=0.90=90%\begin{array}{lrl} \text{ or } & \eta & =\frac{\text{ Output power }}{\text{ Input power }} \\ \text{ or } & \eta & =\frac{V_s I_s}{V_p I_p} \\ \text{ Given, } & V_s I_s & =100 \mathrm{ W}, V_p=220 \mathrm{ V}, I_p=0.5 \mathrm{ A} \\ \text{ Hence, } & \eta & =\frac{100}{220 \times 0.5}=0.90=90 \% \end{array}
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