Question

An ideal transformer, connected to a 240 V mains, supplies a 12V, 150W lamp. Calculate the transformer turns ratio and the current taken from the supply.

Answer 1

Answer n1/ne = V1/V2=240/2=120

P=VI

I=V/P=12/150=3/40AMPERE

Answer 2

The transformer turns ratio is 20/1 and the current taken from the supply is 0.625 A.

Given,

The mains voltage, $V_1$ = 240 V

The supply voltage, $V_2$ = 12 V

The wattage of the lamp, P = 150 W

To find,

The transformer turns ratio,

and the current taken from the supply, $I_1$

Solution,

This problem can easily be solved easily as we know the

turns ratio = $N_1/N_2$ = $V_1$/$V_2$

                               = 240/12

         ⇒ turns ratio = 20/1

Also, $V_1$/$V_2$ = $I_2$/$I_1$

$I_2$ = P/$V_2$

   = 150/12 = 12.5 A

⇒ $I_1$ = $I_2$×$V_2/V_1$ = 12.5 (12/240)

                        $I_1$ = 0.625 A

Hence, we can conclude that the turns ratio = 20/1 and the current taken from the supply is 0.625 A.

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