Paper 3 Transformers Drills

Q1 Power Transmission

A power station transmits $60\mathrm{kW}$ through cables of total resistance $8.0\Omega$.

1. Calculate cable current if transmission voltage is $2.0\mathrm{kV}$. [2]
2. Calculate cable power loss. [2]
3. Calculate cable current and loss if transmission voltage is $20\mathrm{kV}$. [3]
4. Explain why high voltage is used for transmission. [2]

Q2 Transformer Losses

1. Describe copper loss and how it is reduced. [2]
2. Describe eddy-current loss and how it is reduced. [2]
3. Describe hysteresis loss and how it is reduced. [2]
4. Explain why a real transformer cannot be $100\%$ efficient. [1]