What happens when there is an electric current in a wire?

Answer 1

ANSWER

Voltage of the battery and resistance in the wire or lightbulb.

Ohm's Law: E = I * R

E is electromotive force and is measured in volts

I is intensity and is measured in amps

R is resistance and is measured in ohms

Voltage is the pressure that pushes electrons from one atom to the next in the conductor. This flow of electrons (flow of electrons is current) is measured in amps. Resistance is the opposition to current flow. You need enough voltage (pressure) to push the electrons through the resistance to be able to have current flow. Ohm's Law can be rewritten as I = E / R to solve for how much current would flow in a circuit if you know how much voltage was applied to how much resistance.

ANSWERThe previous explanation is an excellent mid-20th century textbook answer to the question, but rather inadequate for what we know in the early-21st century.

THE SHORT ANSWER IS THAT CURRENT IS CAUSED BY POWER (OR BY ENERGY, WHICH IS POWER WITH A TIME FACTOR). Now, on to the details.

What is actually flowing in a DC (direct current) electrical circuit is charge, a fundamental property of matter like mass and time. We still don't really understand what charge and mass and time are, but that doesn't prevent us from understanding how we can use them. Electrons are the easiest place to find charge, because almost everything is made of atoms and the outside of every atom is a cloud of electrons, each electron carrying one charge.

Some materials hang on to their electron clouds and the charges in the clouds very tightly; we call these materials insulators. In other materials, especially metals, the electron clouds are less tightly held; and electrons and their charges are free to leap from cloud to cloud. We call these materials conductors.

So direct current is actually a flow of charges. We measure current by measuring how much chargepasses a particular point in the circuit in one second of time. Notice how current is described using 2 of the most fundamental physical properties that we know of, chargeand time.

But charges cannot just take off and start flowing all by themselves. They need to have the property of energy in order to be able to move. Voltage or EMF is a concept that we use to describe how much energy is present for each charge. "Low voltage" means that there is very little energy for each charge; "high voltage" means that there is a great deal of energy for each charge.

This may make it sound like the charges are carrying the energy, but the relationship is more complicated than that. The electrons and charges trudge rather slowly around the circuit (a few mm or cm per hour), while the energy races from the power source to the far end of the circuit at fantastic speed (a million miles per hour or more). Obviously the energy is not directly attached to the electrons or the charges, but the slow motion of the electrons and charges makes the incredibly fast motion of the energy somehow possible.

Resistance is a property that removes energy from the circuit and moves it someplace else in a different form. It might move the energy in the form of heat in a toaster, it might move the energy in the form of light in a lightbulb, it might move the energy in the form of sound in a stereo or iPod, etc.

The main source of power or energy for our homes and businesses is in the form of AC (alternating current). In an AC circuit, the electrons and charges stay pretty much in one place and slowly wave back and forth. This sets up a power or energy wave called an electromagnetic wave, which is capable of carrying power or energy at a speed of roughly 35 million miles per hour. Because of the electromagnetic nature of AC current, we can use magnetic devices called transformers to raise or lower the voltage or EMF. This is not possible with DC current.

So the best way to move electrical energy long distances is to use AC, while most of our favorite electronic gadgets require DC. Fortunately, it is quite simple to change AC to DC; changing DC to AC is possible but comparitively complicated.

Finally, scientists have devised a system of units to describe specific amounts of the different properties we have been talking about.

The basic unit of power is called the watt.

The basic unit of energy is called the watt-second or joule.

The basic unit of charge is called the coulomb.

The basic unit of current is called the coulomb per second or ampere.

The basic unit of voltage or EMF is called the joule per coulomb or volt.

The basic unit of resistance is called the ohm.

Answer 2

Moving a magnetic field near an electric field or vice versa. Basically: Moving a magnet up and down near the wire. Or moving the wire up and down near a magnet.

Answer

Its voltage that's induced into a conductor, NOT current. Current will only flow, as a result of this induced voltage, provided a load is connected across the wire.

Answer 3

Electrons flow because of electrical attraction and repulsion.

Answer 4

The current flows in one direction only and the electrons cannot choose what direction to go in.