With the aid of a graph, explain the effect of temperature on resistance for electrolytes
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Answer:
Variation of Resistivity in Conductors
We know that current is the movement of free electrons from one atom to the other when there is a potential difference. In conductors no forbidden gap is present between the conduction band and valence band. In many cases both the bands overlap each other. The valence electrons are loosely bound to the nucleus in conductors. Usually metals or conductors have low ionization energy and so they tend to lose electrons very easily. When an electric current is applied the delocalized electrons are free to move within the structure. This is the case that happens in normal temperature.
When the temperature increases the vibrations of the metal ions in the lattice structure increases. The atoms starts to vibrate with higher amplitude. These vibrations in turn causes frequent collisions between the free electrons and the other electrons. Each collision drain out some energy of the free electrons and causing them unable to move. Thus it restricts the movement of the delocalized electrons. When the collision happens the drift velocity of the electrons decreases. This means that the resistivity of the metal increases and thus current flow in the metal is decreased. The resistivity increases means that the conductivity of the material decreases.
For metals or conductors, it is said that they have a positive temperature co – efficient. The value α is positive. For most of the metals, the resistivity increases linearly with increase in temperature for a range of 500K. Examples for positive temperature co – efficient include, silver, copper, gold etc.
Temperature dependence on resistivity for metals
Temperature dependence on resistivity for metals
Variation of Resistivity in Semiconductors
Silicon is a semiconductor. In semiconductors the forbidden gap between the conduction band and the valence band is small. At 0K, the valence band is completely filled and the conduction band may be empty. But when a small amount of energy is applied, the electrons easily moves to the conduction band. Silicon is an example for semiconductor. Under normal circumstances silicon act as a poor conductor. Each silicon atom is bonded to 4 other silicon atoms. The bonds between these atoms are co valent bonds where the electrons are in fixed positons. So at 0K, the electrons does not move within the lattice structure.
Variation of Resistivity in Semiconductors
Explanation: