Step-up transformers are used before long-distance electrical power transmission mainly to:
AIncrease current while reducing voltage for improved safety
BConvert alternating current directly into direct current
CIncrease voltage and reduce current, minimizing resistive (Joule) losses
DStore electrical energy chemically for later distribution
Answer & Solution
Correct answer: C. Increase voltage and reduce current, minimizing resistive (Joule) losses
1. Power transmitted equals voltage times current, so for a fixed power, raising voltage lowers the current needed.
2. The text explains: "Transformers are widely used in the electric power industry to increase voltages—called step-up transformers—before long-distance transmission via high-voltage wires."
3. It continues: "The lower current...in the transmission wires reduces the Joule losses," the heating caused by the wire's resistance.
4. So step-up transformers raise voltage specifically to cut the current and the resulting resistive power loss over long wires -- they do not convert AC to DC or store energy.
_Source: OpenStax Physics Ch 20 "Magnetism", p.691 §20.2 Motors, Generators, and Transformers_
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