Why the resistance of metals increase with increase in temperature?

Answer 1

In a wire, electrons are moving close to the speed of light, but they normally collide with the crystal lattice atoms and scatter (no fixed directions; can be deflected forward or backward or sideways). Adding an electric field to the wire (applying the ends of the wire to the terminals of a battery), we can nudge the electrons to have a net movement (an electron moving 10 steps forward but nine steps back has a net movement of one step forward) in one direction (the battery is supplying a DC current). When one electron leaves the wire (at the positive terminal of the battery), another electron has to enter the wire from the negative terminal to maintain electrical neutrality of the wire almost instantly. Hence the flow of information is still near the speed of light. Resistance is the measure of how quick is the net movement of electrons -- the slowly the net movement, the higher the resistance. A higher temperature makes the electrons (like going nowhere faster) and the lattice atoms (more vibration) more excited than a lower temperature. The extra atomic vibration makes the electron transition across a wire more difficult, although the electrons have sped up.

An analogy is filling a room with two exits, one to the right and the other to the left, with people standing. These people are ordered to give a push of any approaching person in a random direction (unpredictable). The room is situated on a level ground. You enter from the right by accident. You start bumping into the people in the room. Each person you approach gives you a push in a totally random direction. You may get out the exit to the right or move to the wall to the far end -- totally random. Note that no matter how fast you run, you feel you are not going anywhere in particular. Adding an electric field is like the room is being tilted so that the right-hand exit is higher than the left-hand exit. You have a net movement going to the left because of the aid of gravitational pull. A higher temperature means you run at a faster speed and the other people in the room are shaking randomly too. The resulting chaos slow your net movement to the left.

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Answer 2

As temperature increases, the molecular activity of the wire increases. The atoms also become slightly further apart. This makes it more difficult for free electrons to cascade from atom to atom, thus increasing the resistance.

Answer 3

Resistance is a phenomena that restricts the flow of electrons in the metal. The current of electrons travels along the surface of the metal wire. Increased temperature basically agitates the atoms that comprise the wire and electrons are more impeded in their travel along the wire. The minimum resistance is achieved as the temperature approaches absolute zero.

Answer 4

Because the atoms in the metal move around faster and faster as the temperature increases making it harder for the free electrons to flow smoothly from atom to atom and conversely, the resistance decreases as temperature falls because the atoms in the metal become more and more stationary and thus the free electrons can easily flow smoothly from atom to atom.