The grid raises a line's voltage. What happens to the current needed to deliver the same power?
A toaster in your kitchen glows with energy that set out from a power station far away. Here is the whole journey, stage by stage.
Every stage runs on something this topic taught. This lesson walks the journey and names the principle at each stage.
Stage 1: the power station. A turbine spins a coil in a magnetic field.
The generator effect turns that motion into an EMF. The spinning coil's EMF alternates, so the grid runs on AC.
Stage 2: the step-up transformer. Before the long-distance lines, it raises the voltage.
Raising the voltage lowers the current, so the lines waste far less energy as heat.
Stage 3: the transmission lines. They carry the power across the country at very high voltage and small current.
Stage 4: the step-down transformers. Near the city, and again near your street, they lower the voltage in stages.
The last one brings it to the 120 V your home's outlets supply.
Which device makes the alternating EMF at the power station?
Where in the journey does the step-up transformer sit?
Electricity reaches a bakery's ovens from a dam's turbines. Trace the journey, naming the device and the principle at each stage.
Stage 1: the dam's turbines spin coils in magnetic fields. The generator effect makes an alternating EMF.
Stage 2: a step-up transformer raises the voltage for the long-distance lines.
Stage 3: the lines carry the power at high voltage and small current, wasting little as heat.
Stage 4: step-down transformers near the town lower the voltage to the 120 V the bakery's outlets supply.
Generator, then step-up transformer, then transmission lines, then step-down transformers, then the ovens.
A long-distance line runs at 345,000 V, but a home's outlets supply 120 V. What must happen between the line and the home, and why?
The line's voltage is far higher than the voltage homes use.
Step-down transformers lower the voltage in stages on the way to the street.
Step-down transformers must lower the voltage from the line's 345,000 V to the 120 V homes use.
The transmission lines run at a very high voltage. Which device lowers it before homes use it?
In which order does electrical energy pass these stages, from power station to home?
At the power station, a coil spins between magnet poles and an EMF appears across it. Which principle is at work?
A storm knocks out the step-down transformers near a town, though the long-distance lines still run. Why can the town's homes not be supplied straight from the lines?