Question

A transformer connected to 220v mains is used to light the lamp of rating 100w and 110v. If the primary current is 0.5A. Find the efficiency of the transformer is

Answer 1

Input power = 220*0.5=110
output power = 100
efficiency of transformer =
(output power/input power) *100
= (100/110)*100
= 90.91%

Answer 2

The efficiency of the transformer is 90.9%

• Transformer is an electrical device which is used to transfer electrical energy from one electrical circuit to another.
• Efficiency of transformer is defined as the ratio of output power to input power.
• Efficiency of transformer = $\frac{P_{out} }{P_{in} }$ x 100
• Most of the transformers are efficient but not 100% efficient due to some power loss when it transfer from primary coil to secondary coil.
• PROBLEM:

                  Primary                      Secondary

                $V_{p}$ = 220 V                      $V_{s}$ = 110 V

                $I_{p}$ = 0.5 A                        

               $P_{in}$ =  $V_{p}I_{p}$                        $P_{out} = V_{s}I_{s}$

                     = 220 x 0.5                       = 100 W

                     = 110 W

• Efficiency of transformer = $\frac{100}{110}$ x 100

                                                  = 90.9%