Question

High voltage power lines transmit electrical energy at 240,000 V. Before the current reaches your home, the voltage is decreased to the standard voltage for a wall socket. If a single step-down transformer is used, what is the ratio of turns in the primary coil to the secondary coil?

Answer 1

Transformer is used to change the voltage from higher value to lower value

It is done by changing the number of coils in primary and secondary coils

The working equation is given as

$\frac{V_s}{V_p} = \frac{N_s}{N_p}$

here we have

$V_s$ = Secondary coil voltage = 120 V

$V_p$ = Primary coil voltage = 240,000 V

$N_s$ = Turns in secondary coil

$N_p$ = Turns in primary coil

Now by using the equation above

$\frac{120}{240,000} = \frac{N_s}{N_p}$

now we have

$\frac{N_p}{N_s} = \frac{240,000}{120}$

$\frac{N_p}{N_s} = 2000$

so the ratio must be 2000