- #1

Clara Chung

- 304

- 14

## Homework Statement

Electricity generated in the power station is stepped up by a transformer X from 25kV to 400kV before transmitted by overhead cable. Then it is stepped down to 200V through another transformer Y before entering domestic circuits. Assume all transformers are ideal.

Given the power transmitted through the cables and the total resistance of the cables is 4x10^3 kW and 1Kohm respectively. Find

(I) the electricity is not stepped up by X (3marks)

(II) the electricity is stepped up by X (2 marks)

## Homework Equations

Ip / Is = Ns / Np

## The Attempt at a Solution

In (I),I tried to find out the power lost in the cable by finding the current in the transmitting cable by 4 x 10^3 x 1000 /25000 x (25 /400)=10A, Power=10^2 x 1000 = 100000W, I thought it was the electricity NOT stepped up by X, but the answer turned out to be 100000W is the electricity stepped up by X(the answer of (II)). I don't understand what does the question mean.