An electric scooter's motor runs at 30 V and carries 5 A. What is its power, in W?
The towers that cross the countryside carry electricity at hundreds of thousands of volts. A home outlet supplies 120 V. Why does the grid send it so high?
Back in the Circuits topic you saw electrical power: P = IV. That one equation is the reason.
A power line must deliver a fixed amount of power: whatever the city is using.
P = IV: the same power can travel as a large current at a low voltage, or as a small current at a high voltage.
Here is one delivery, 240,000 W, done both ways.
At 1200 V, the line must carry 200 A. At 120,000 V, it carries 2 A.
Now the cost. A current heats the cable it flows through, and a larger current heats it far more.
The 200 A line wastes far more energy heating the cables than the 2 A line does.
Many long-distance lines in the United States run at 345,000 V.
The grid raises a line's voltage. What happens to the current needed to deliver the same power?
A line's current gets smaller while it delivers the same power. What happens to the heating of its cables?
The 240,000 W delivery runs at 120,000 V instead of 1200 V. Explain why far less energy is wasted.
The line must deliver the same power either way.
P = IV, so at 120,000 V the line carries 2 A instead of 200 A.
A smaller current heats the cables far less.
The high-voltage line carries a far smaller current, so it wastes far less energy heating the cables.
A step-up transformer sits between a power station's generator and the long-distance lines. State its job.
It raises the voltage for transmission.
The raised voltage lowers the current needed to deliver the same power.
The smaller current wastes far less energy heating the cables.
It raises the voltage so the lines carry a smaller current and waste far less energy as heat.
A student says the grid uses very high voltage to push the electricity along faster. What is the real reason?
Line A and line B deliver the same power through identical cables. Line A runs at ten times line B's voltage. Which line's cables waste less energy as heat?
Line A delivers the same power as line B, at ten times the voltage. How does line A's current compare with line B's?
A solar farm steps its output up to 345,000 V before the long line to the city. Why?