A large power plant generates electricity at 12.0 kV. Its old transformer once converted the voltage to 390 kV. The secondary of this transformer is being replaced so that its output can be 515 kV for more efficient cross-country transmission on upgraded transmission lines. (a) What is the ratio of turns in the new secondary compared with turns in the old secondary

1.32 is the turns ratio

Explanation:

Note that The transformer steps up the voltage from 12000 V to 390000V

12000 V is the primary and in the secondary it is 390000 V in old transformer

If n₁ be no of turns in primary coil and n₂ be no of turns in secondary coils

the formula is

n₂ / n₁ = voltage in secondry / voltage in primary

n₂ / n₁ = 390000 / 12000

ratio of turns in old transformer is 32.5

ratio of turns in new transformer

n₃ / n₁ = 515 / 12 ( n₃ is no of turns in the secondary of new transformer )

= 42.9

T he ratio of turns in the new secondary compared with the old secondary

n₃ / n₂ = 42.9 / 32.5

= 1.32

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it