KCET2015PhysicsCurrent Electricity
A transformer is used to light ( 100 ~W -110 ~V ) lamp from ( 220 ~V ) mains. If the main current is ( 0.5 ) A, the efficiency of the transformer is
Options
- A( 90 % )
- B95 %
- C( 96 % )
- D( 99 % )
Correct answer
A. ( 90 % )
Step-by-step solution
Given, transformer lights 100 ~W -100 ~V lamp; input voltage =220 ~V ; input current =0.5 ~A Therefore, efficiency = Output power Input power 100 Here, output power =100 ~W Input power = Input voltage Input current =220 0.5=110 ~W Thus, = 100 110 100=90 %