Which kind of current repeatedly reverses its direction?
A bicycle dynamo presses against the tire. When the rider pedals, the wheel spins the dynamo, and the headlamp lights.
The dynamo is one member of a whole family of machines.
Inside the dynamo, a coil sits between magnetic poles, and the wheel spins the coil.
The spinning coil is a conductor moving through a magnetic field. That is relative motion, so an EMF is induced.
A machine that produces its EMF by rotating a coil in a magnetic field is called a generator.
The dynamo is a generator. So is the huge machine a power station turns.
A generator is the motor arrangement run in reverse. Here is the pair again: the motor effect turns current into motion; the generator effect turns motion into current.
One more fact about every generator: the EMF it produces is alternating.
When the rider pedals steadily, the dynamo's lamp runs on AC. The current through it reverses again and again.
At a fair, pedaling a stationary bike spins a coil between magnets, and a row of bulbs lights. What is the coil-and-magnets machine called?
The machine produces its EMF by rotating a coil in a magnetic field.
A machine that does that is called a generator.
The machine is a generator.
A generator produces its EMF by doing what?
What kind of EMF does every generator produce: steady one-way, or alternating?
A generator rotates a coil in a magnetic field.
The EMF a generator produces is alternating.
Every generator produces an alternating EMF.
Which kind of EMF does the rotating-coil generator produce?
Zara says a generator is the motor arrangement run in reverse: spin the coil, and an EMF comes out. Is Zara correct?
Which statement describes a generator?
A river turbine spins a coil between magnets, lighting a dock lamp. Which of the following is the machine?
A generator lights a cabin lamp. Which statement about the current in the lamp is correct?