# Temperature Coefficient of Resistance

_{1}resistance at t

_{1}

^{o}C and after raising the temperature, its resistance becomes R

_{2}at t

_{2}

^{o}C. This rise in resistance (R

_{2}- R

_{1}) with rise in temperature (t

_{2}– t

_{1}) depends on following things – By combining above effects, Where, α is the

**temperature coefficient of resistance**of material at t

_{1}

^{o}C.

From Equation (1) If at a particular temperature, we know the resistance and temperature coefficient of resistance of material, we can find out the resistance of material at other temperatures by using equation (2).

The Temperature Coefficient of Resistance of some Materials or Substances
The **temperature coefficient of resistance** of some materials / substances at 20^{o}C are listed below-

Sl. No. | Material / Substances | Chemical Symbol / Chemical composition | Temperature coefficient of resistance /^{o}C (at 20^{o}C) |

1 | Silver | Ag | 0.0038 |

2 | Copper | Cu | 0.00386 |

3 | Gold | Au | 0.0034 |

4 | Aluminum | Al | 0.00429 |

5 | Tungsten | W | 0.0045 |

6 | Iron | Fe | 0.00651 |

7 | Platinum | Pt | 0.003927 |

8 | Manganin | Cu = 84% + Mn = 12% + Ni = 4% | 0.000002 |

9 | Mercury | Hg | 0.0009 |

10 | Nichrome | Ni = 60% + Cr = 15% + Fe = 25% | 0.0004 |

11 | Constantan | Cu = 55% + Ni = 45% | 0.00003 |

12 | Carbon | C | - 0.0005 |

13 | Germanium | Ge | - 0.05 |

14 | Silicon | Si | - 0.07 |

15 | Brass | Cu = 50 - 65% + Zn = 50 - 35% | 0.0015 |

16 | Nickel | Ni | 0.00641 |

17 | Tin | Sn | 0.0042 |

18 | Zinc | Zn | 0.0037 |

19 | Manganese | Mn | 0.00001 |

20 | Tantalum | Ta | 0.0033 |

Effect of Temperature on Temperature Coefficient of Resistance of a Material
The temperature coefficient of resistance of a material is also changes with temperature.
If α_{o} is the temperature coefficient of resistance of material at 0^{o}C, then from equation (2), the resistance of material at t^{o}C,
Where, R_{0} is the Resistance of material at 0^{o} C
Similarly, if the temperature coefficient of resistance of material at t^{o}C is αt, then the resistance of the material at 0^{o}C, from equation (2)
Where, R_t is the Resistance of material at t^{o} C
From equation (3) and (4)
Where, α_{1}and α_{2} the temperature coefficient of resistance of material at t_{1}^{o}C and t_{2}^{o}C respectively.
Hence, if we know the **temperature coefficient of resistance** of a material at a particular temperature, we may find out the temperature coefficient of material at any other temperature by using equation (6).
The conducting material are having large and positive temperature coefficient of resistance. Therefore, the resistance of conducting material (metals) rise with rise of temperature.

The semiconductors and insulating material are having negative temperature coefficient of resistance. Therefore, the resistance of semiconductors and insulators decrease with rise in temperature.
Alloys, such as manganin, constantan etc. are having very low and positive **temperature coefficient of resistance**. Therefore, the resistance of alloys increase with rise in temperature but this rise in resistance is very low (almost negligible) as compare to metals, which makes these alloys suitable for using in measuring instruments.