Suppose you have a 120 volt, 20 amp circuit which only has a light bulb connected. When measuring the voltage going to the light bulb my meter reads 120 volts. The basics taught me that a circuit is a circle, so the back and forth movement of electrons continues after the light bulb along the neutral wire back to the socket etc. So, why isn't there voltage on the neutral wire? I'm assuming there has to be current in order for the circuit to work. If so, is there current without voltage? Thanks for any help with this!
[Physics] Current without voltage
electric-circuitselectric-currentelectricityvoltage
Related Solutions
How do voltage and voltage drops over a circuit relate to work done?
The Volt unit is energy normalized to unit charge; Joule per Coulomb.
Since the Amp unit is Coulomb per second, the product of the voltage across and current through a circuit element is the power associated with the circuit element.
For a DC circuit, voltage and current are constant thus the energy delivered or supplied by a circuit element over some period of time is the product of the voltage across, the current through, and the elapsed time.
Now, the rest of your question contains misconceptions that are too numerous to untangle here. I recommend that you do some more reading and careful thinking about, in particular, basic circuit laws. For example, Ohm's Law immediately gives you the answer to your question "Does voltage drop over a resistor decrease as current decreases?"
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.
Also, I recommend perusing William J Beaty's "Electricity Misconceptions Spread by Textbooks" site.
For a start, take a look at Electric current is a flow of energy? Wrong.
Because of electromagnetic forces, all of the electrons in the wire are displaced towards A with a certain velocity causing a positive current towards B.
The electrons have a small drift velocity, not moving much.
Although your light turns on very quickly when you flip the switch, and you find it impossible to flip off the light and get in bed before the room goes dark, the actual drift velocity of electrons through copper wires is very slow. It is the change or "signal" which propagates along wires at essentially the speed of light.
A single electron does not go from A to B. Think of it as each electron pushing the next one, and the signal travels with the velocity of light ,maximum, down the wire.
This drift of electrons heats up the highly resistive filament wire in the bulb and makes it glow.
True.
But I don't understand why they are able to move back and forth. Specially if length of the wire was large, say 3 * 10^8 meters, then would the movement of electrons on one end of the wire be "in sync" with movement of electrons on the other end?
Why not? When the field changes at A and B the change propagates by electrons moving back and forth over an average position. Similar to water waves, the atoms do not move much from their position, the energy is transferred atom by atom. In the case of electric fields and electrons the field is built up at the microscopic scale by the motion in situ of the electrons, in a sinusoidal way.
Very long wires enter the realm of special relativity and the limit of the velocity of light in transferring effects of fields.
Best Answer
Voltage is the difference in potential between two wires. You can't say the "hot" wire has any sort of voltage by itself. Just as you can't say the "neutral" wire has any voltage by itself. The voltage is the measure of electrical potential between the two.
When you connect the light bulb between the two it provides a path for current to flow from high voltage to low voltage.
If you want to read about the specifics of this, Kirchoff's circuit laws (and especially Kirchoff's Voltage Law) are the place to start.