Electricity & Megnetism

# Electric charges in motion

The movement of charged particles in conductors is different from the movement of particles in empty space. After the application of a potential difference, the free charged particles are momentarily accelerated, suffering inelastic collisions with the fixed particles of the conductor.

When we apply a potential difference VA – VB , it originates, inside a conductor, an electric field E , whose direction is from the positive pole to the negative pole. Inserted in this electric field, the electrons are subject to an electric force Fel = qE in the opposite direction to the electric field vector. Electrons acquire orderly motion. We call this movement of charged particles ELECTRIC CURRENT.

## Electric current intensity

We call the average intensity of electric current the ratio between the variation of the charge ?q, which crosses a conductor, by the variation of time, that is,

i = Δ q
Δ t

In this case, we can observe that the intensity of electric current is constant.

When the current varies with time, instantaneous current intensity is defined, the limit of the average intensity, when the time Δt approaches zero.

Δt→0   Δ t

## Electric circuit

An electrical circuit is the set of devices where an electric current can be established.

## Electric current effects

When passing through a conductor, electric current can cause different effects, depending on the nature of the conductor. The most common and most important are:

Physiological effect: It is the passage of electric current through living organisms. Called an electric shock, the current passes through the body and acts directly on the nervous system, causing muscle contractions.
In this case, if the intensity is between 10 mA and 3 A, this current can be fatal, as it crosses the entire chest, reaching the heart with sufficient intensity to alter the heart rhythm.

Joule Effect: When moving, the electrons collide with the conductor particles, which receive energy and begin to vibrate with greater intensity. This variation in vibration causes an increase in temperature. In general, this effect is applied in heaters, showers, etc.

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