Alloy: The resistance of almost all alloys increases with increase in temperature but the rate of change of resistance is less than that of metals. Fundamental of Electrical Engineering | Effect of Temperature On Resistance| Resistance Temperature Coefficient, The change in resistance of a material with the increase in temperature can be expressed b means of the temperature coefficient of resistance.Consider a conductor having resistance, Directly proportional to the initial resistance, Directly proportional to the rise in temperature, Depends on the nature of the material for conductor metals and alloy, Effect of Temperature On Temperature Coefficient of Resistance, The specific resistance or resistivity of a material depends on temperature. For most materials, how does an increase in temperature affect the resistivity? The “alpha” (α) constant is known as the temperature coefficient of resistance and symbolizes the resistance change factor per degree of temperature change. Temperature has little effect on the resistance of some alloys, such as constantan.For a few materials, including carbon and other semiconductors, the resistance decreases as the temperature increases.. In fact, for the different type of materials, the amount of change in resistance due to change in temperature is different which are discussed as follow. Figure 1 shows the resistance of a conductor increases with temperature. The temperature dependence of resistivity (or its reciprocal, conductivity) can only be understood with quantum mechanics. Let ρt1 and ρt2 be the resistivity at temperature t1°c and t1°c respectively. Resistivity has inverse relationship with length of wire….so by increasing the temperature the metallic wire would expand and length increases due to which resistivity should have to decrease but according to above explaination it is increased.how? I want to help you achieve the grades you (and I) know you are capable of; these grades are the stepping stone to your future. In the equation ρ0 is the resistivity at a standard temperature, ρt is the resistivity at t0 C, T0 is the reference temperature and α is the temperature co – efficient of resistivity. The electrical resistance changes with the change of temperature. This shows that the resistivity is related to the number density n of free electrons in the material and relaxation time t. The variation of resistivity of material with temperature is different in different materials and it is discussed below: (a)    Metals: In most metals, number density n of free electrons does not change with temperature but an increase in temperature increases the amplitude of vibration of lattice ions of the metal. ρt = ρ0 [1 + α (T – T0) is the equation that shows the relation between the temperature and the resistivity of a material. Rt2  =  Rt2[1 + αt2 (t1 – t2)] [1 + αt1 (t2 – t1)], 1 = [1 + αt2 (t1 – t2)] [1 + αt1 (t2 – t1)], =  [1 – αt2 (t2 – t1)] [1 + αt1 (t2 – t1)], Note: If the temperature changes from 0°C to t°C then. Hence, conductivity increase and resistance decrease with increase in temperature. The increase in temperature will increase the randomness so more collisions so more resistance. So resistivity decrease. The ratio m/ρt1 is called the temperature coefficient of resistivity at t1°c and is almost equal to α1. A certain winding made up of copper has a resistance of 100Ω at room temperature. When we increases the temperature the amplitude of vibration of atoms increases as result of which the number of collision among the electrons and atom increases, and hence resistances increases. The resistance increases as the temperature of a metallic conductor increase, so the resistance is directly proportional to the temperature. Similarly, compaction condition of the soil affects resistivity. 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