Quick questions on Generators, transformers and AC power transmission: VCE Physics Unit 3

A transformer is two coils wound around a common iron core. AC in the primary coil produces a changing magnetic flux in the core. The same changing flux passes through the secondary coil, inducing an EMF.

The power lost as heat in transmission lines of resistance $R$ depends on the current squared:

The transmission cables form a voltage divider with the load. Voltage delivered to the load:

Uses slip rings: a continuous ring on each end of the coil, with brushes feeding the external circuit. As the coil rotates, the current reverses every half-turn. The external circuit sees alternating current.

Uses a split-ring commutator (the same device as in a DC motor). It swaps the brush connections every half-turn, so the external current always flows in the same direction. The output is a series of half-wave humps; with many coils at different angles, the output approaches a smooth DC voltage.

State the ideal-transformer voltage and current ratios. [2 marks]

A transformer steps $240$ V down to $12$ V. (a) Calculate the turns ratio. (b) Find the primary current when the secondary delivers $5.0$ A.

Refer to Loy Yang transmission. (a) Calculate the turns ratio for stepping $23$ kV to $500$ kV. (b) Determine the current on the line if generator output is $10\,000$ A.