Generator transformers are ________ transformers.

The answer for generator transformers is 1) Step-up.

Concept:

Generator transformers increase the voltage generated by power plants from around 20,000 to 400,000 volts for efficient transmission through power lines over long distances. This significantly reduces the current flowing through the lines, minimizing energy losses due to heat dissipation.

Therefore, generator transformers function as step-up transformers to facilitate efficient power transmission from the source (power plant) to the distribution network.

Here's a short explanation of the other options:

1. Step-down: These transformers decrease voltage at various stages of power distribution, ultimately bringing it down to safe and usable levels (around 120V or 240V) for homes and businesses.
2. One-one: These transformers maintain the same voltage level on both sides (primary and secondary windings) and are mainly used for isolation or impedance matching purposes.
3.  Auto: Unlike generator transformers, auto transformers have a single winding tapped at some point, providing both input and output terminals. They are less efficient than conventional transformers for large voltage changes but find applications in specific cases.