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Module 1: Introducción a los sistemas eléctricos

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XSIQ
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Physics - Resistance

Resistance

The term resistance is self-describing. All conductors have some
resistance to the flow of electricity. Metals, are good conductors and have
low resistances. Ceramic materials, on the other hand, have much higher
resistances. George Ohm discovered that some materials maintain a constant
resistance regardless of the rate and energy of the electricity flowing
through them. The result is that, as the voltage applied to the device
increases, the amount of current that is able to flow through the device
increases proportionally. Items displaying this property are called ohmic
conductors [1], and Ohm's Law applies:

a graph of the I-V characteristics of an ohmic device will be linear, as
shown.

Non-ohmic devices have disproportionate changes in the current flowing as
the applied voltage is altered. This is often because the actual resistance
value of the device alters with different applied voltages. A tungsten
filament, for example, heats as current flows through it, and this greatly
affects its resistance value.

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