Wht is resitivity? and Potenial Differecces?
Resistivity is the resistance provided by a material of 1 unit length and 1 unit area.
It is denoted by the 'rho '
Factors on which resistvity depends on:
1. It is inversevly proportational to temprature
2. It depends on the nature of the material
Unit of Resistvity is Ohm Metre
Resistivity = Resistance (length/area)
Resistivity = Ohm (metre/metre2) where metre and metre cancel
Resistivity = Ohm metre
Potential difference is the difference in electric potential between any two points in an electric field or in a circuit.
Let's begin with the Ohm's Law
It states that the amount of current (I) flowing through a material (say a wire) is directly proportional to the voltage (V) applied across its ends. Mathematically, it is given as
V ? I
V = RI
here R is a constant of proportionality also known as the resistance.
So, the resistance of a material following the Ohm's Law will always stay constant for all values of external voltage applied.
Now, using this principle, we can distinguish materials as either being Ohmic or Non-Ohmic in nature. Such that,
Ohmic materials follow the Ohms' law as the resistance remains unaffected even if we change the applied voltage (which alters amount of current flowing).
The V-I graph in this case shows a linear trend, as follows
So, If it is a straight line with a positive gradient then the resistor is following Ohm's law V=IR. The gradient is the component's resistance.
Non-Ohmic materials, do not obey the Ohm's Law, as the resistance varies with applied voltage.
The V-I graph in this case would show a gradual curved slope, as follows
Resistivity is defined as the resistance offered by a cube of a material of side 1 m when current flows perpendicular to its opposite faces. Its S.I. unit is ohm-meter (?m). Resistivity, ? = RA/L
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