Which unit is an EMF measured in?
Back in the Circuits topic, you saw that a current flows only around a complete circuit.
Here is a coil whose two ends are connected to nothing. The loop is open. A magnet moves through the coil anyway. Is anything induced?
Yes. While the magnet moves, an EMF is induced across the coil's two open ends.
An EMF is a voltage, and a voltage can exist with no current flowing.
A battery on a shelf shows the same thing: it is connected to nothing, yet there is 1.5 V across its terminals.
The open coil is like that battery while the magnet moves. The EMF is there, and no current flows. No current flows because the circuit is not complete.
Now the ends are joined through a meter, making a complete loop. The same moving magnet induces the same EMF. And now the EMF drives a current around the loop.
A magnet moves through a coil whose ends hang apart in the air. Is an EMF induced, and does a current flow?
The magnet is moving, so an EMF is induced across the coil's ends.
The ends hang apart, so the circuit is not complete.
A current flows only around a complete circuit.
An EMF is induced across the ends, and no current flows, because the circuit is not complete.
The same coil's ends are then joined to form a loop, and the magnet repeats its move. What changes?
The moving magnet induces the same EMF as before.
The joined ends make the circuit complete.
So the EMF now drives a current around the loop.
The EMF is unchanged, and now it drives a current around the complete loop.
A magnet moves through a coil joined into a complete loop. Does a current flow?
Tara says no EMF can be induced unless the coil is part of a complete circuit. Is Tara correct?
Finn says an open coil can have an induced EMF across its ends while no current flows. Is Finn correct?
A magnet moves through a coil whose ends are connected to nothing. Which statement is correct?
A magnet moves through an open-ended coil, and no current flows. What is missing for a current to flow?
A coil in a complete loop with an ammeter carries a current while a magnet moves through it. The loop is then cut open and the same move is repeated. What happens on the repeat?