As temperature increases, what the hell happens to current and resistance??

From PPQ's, what I have discovered is that as temperature increases, the current decreases, and the resistance increases. But if the current increases, then the temperature also increases. How is this possible?
So if the temperature increases, the atoms in the metal are vibrating more so there is more resistance and less current can flow. That makes sense to me. But then why does a fuse melt when the current increases above a certain level - surely the temperature must increase with current? I'm really bloody confused right now.

Reply 1

K-Man_PhysCheM

17

Original post by Eulex

From PPQ's, what I have discovered is that as temperature increases, the current decreases, and the resistance increases. But if the current increases, then the temperature also increases. How is this possible?
So if the temperature increases, the atoms in the metal are vibrating more so there is more resistance and less current can flow. That makes sense to me. But then why does a fuse melt when the current increases above a certain level - surely the temperature must increase with current? I'm really bloody confused right now.

As current increases, there are more collisions between metal ions and electrons. On each collision, electrons transfer some of their energy to metal ions. At high current, with lots of collisions, the metal ions begin to vibrate more, so their temperature increases.

This in turn causes resistance to increase, and so if potential difference remains constant, then current will decrease again and an equilibrium is established.

However, in a broken circuit, a surge of high current can come out of nowhere and suddenly heat up the wire so it melts. As it heats up, the current would decrease if pd remained constant, but in such a scenario the heating is either too fast or voltage keeps increasing, and so the fuse blows to break the circuit and prevent an even greater overload of current and pd that could cause an electrical fire.

Reply 2

f2trappy%

1

Original post by Eulex

From PPQ's, what I have discovered is that as temperature increases, the current decreases, and the resistance increases. But if the current increases, then the temperature also increases. How is this possible?
So if the temperature increases, the atoms in the metal are vibrating more so there is more resistance and less current can flow. That makes sense to me. But then why does a fuse melt when the current increases above a certain level - surely the temperature must increase with current? I'm really bloody confused right now.

my exact question

As temperature increases, what the hell happens to current and resistance??

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