Electric current and current flow

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Electric current and current flow

The electric field direction within a circuit is by definition the direction that positive test charges are pushed. Thus, these negatively charged electrons move in the direction opposite the electric field.

But while electrons are the charge carriers in metal wires, the charge carriers in other circuits can be positive charges, negative charges or both.

In fact, the charge carriers in semiconductors, street lamps and fluorescent lamps are simultaneously both positive and negative charges traveling in Electric current and current flow directions. Ben Franklin, who conducted extensive scientific studies in both static and current electricity, envisioned positive charges as the carriers of charge.

As such, an early convention for the direction of an electric current was established to be in the direction that positive charges would move. The convention has stuck and is still used today. The direction of an electric current is by convention the direction in which a positive charge would move.

Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery.

Electrons would actually move through the wires in the opposite direction. Knowing that the actual charge carriers in wires are negatively charged electrons may make this convention seem a bit odd and outdated.


Nonetheless, it is the convention that is used worldwide and one that a student of physics can easily become accustomed to. Current versus Drift Speed Current has to do with the number of coulombs of charge that pass a point in the circuit per unit of time.

Because of its definition, it is often confused with the quantity drift speed. Drift speed refers to the average distance traveled by a charge carrier per unit of time.

Electric current and current flow

Like the speed of any object, the drift speed of an electron moving through a wire is the distance to time ratio. The path of a typical electron through a wire could be described as a rather chaotic, zigzag path characterized by collisions with fixed atoms. Each collision results in a change in direction of the electron.

Yet because of collisions with atoms in the solid network of the metal conductor, there are two steps backwards for every three steps forward. With an electric potential established across the two ends of the circuit, the electron continues to migrate forward.

Progress is always made towards the positive terminal. Yet the overall effect of the countless collisions and the high between-collision speeds is that the overall drift speed of an electron in a circuit is abnormally low.

A typical drift speed might be 1 meter per hour. One might then ask: How can there by a current on the order of 1 or 2 ampere in a circuit if the drift speed is only about 1 meter per hour? Current is the rate at which charge crosses a point on a circuit.

A high current is the result of several coulombs of charge crossing over a cross section of a wire on a circuit. If the charge carriers are densely packed into the wire, then there does not have to be a high speed to have a high current. That is, the charge carriers do not have to travel a long distance in a second, there just has to be a lot of them passing through the cross section.

Current does not have to do with how far charges move in a second but rather with how many charges pass through a cross section of wire on a circuit.

To illustrate how densely packed the charge carriers are, we will consider a typical wire found in household lighting circuits - a gauge copper wire. Each copper atom has 29 electrons; it would be unlikely that even the 11 valence electrons would be in motion as charge carriers at once.

If we assume that each copper atom contributes just a single electron, then there would be as much as 56 coulombs of charge within a thin 0. With that much mobile charge within such a small space, a small drift speed could lead to a very large current.

To further illustrate this distinction between drift speed and current, consider this racing analogy. Suppose that there was a very large turtle race with millions and millions of turtles on a very wide race track.

Turtles do not move very fast - they have a very low drift speed. Suppose that the race was rather short - say 1 meter in length - and that a large percentage of the turtles reached the finish line at the same time - 30 minutes after the start of the race.

In such a case, the current would be very large - with millions of turtles passing a point in a short amount of time. In this analogy, speed has to do with how far the turtles move in a certain amount of time; and current has to do with how many turtles cross the finish line in a certain amount of time.

The Nature of Charge Flow Once it has been established that the average drift speed of an electron is very, very slow, the question soon arises: Why does the light in a room or in a flashlight light immediately after the switched is turned on?Electric current is a measure of the flow of charge, as, for example, charge flowing through a wire.

The size of the current is measured in amperes and symbolized by lausannecongress2018.com ampere of current represents the passage of one coulomb of charge per second,.

What is Electric Current?

Electric current is the rate at which electric charge flows past a point on the electric circuit. Water current is the rate at which water flows past a point on the water circuit. As such, current is analogous to the number of gallons of water flowing into, along, and out of a slide per unit of time.

Sep 20,  · its lightning, for a more simple answer..

Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity. They were wrong! Electron Flow is what actually happens and electrons flow out of the negative terminal, through the circuit and into the positive terminal of the source. Therefore, one-ampere current is equal to X 10 ^ 18 electrons should flow in one second. Electric current is widely used in household and industrial appliances. Two types of electrical current are, one is alternating current is called an AC current and direct current is called us DC current. 1. water analogy: the flowing water is the flowing charge (aka electric current). the water pressure is the voltage, and the water wants to flow from high pressure to low pressure, and the pump is the voltage source, which pushes the water up to high pressure.

electric current flow is the movement of charges. Most often, however, we consider electric current flow to be moving electrons, or electron current flow. Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source.

This was the convention chosen during the discovery of electricity. Like a river current is the flow of water molecules, electrical current is the flow of charged particles. In this lesson, we're going to explore what electrical current .

Electric current is electric charge in motion. It can take the form of a sudden discharge of static electricity, such as a lightning bolt or a .

Electric current - Wikipedia