A copper wire and a solution of copper sulphate are each joined to a battery and a meter…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A copper wire and a solution of copper sulphate are each joined to a battery and a meter. The meter shows the current. Both are warmed slowly by . Say what happens to the current in each, and explain the difference in terms of what carries the current.
Need a reminder? The key ideaShow
The cell constant is , in . The conductivity is , in , and . A cell is calibrated with potassium chloride: . A solution of potassium chloride has at .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The wire. Electrons carry the current. When the wire is warmed, its atoms vibrate more and scatter the electrons more often. The resistance rises, so the current falls.
Step 2. The solution. Ions carry the current. When the solution is warmed, the water flows more easily and the ions move faster. The resistance falls, so the current rises. For a weak electrolyte, more of the molecules also split into ions.
Step 3. The difference. The carriers are different. Heat gets in the way of the electrons in a metal, and it helps the ions in a solution.
Answer: the current in the wire falls and the current in the solution rises.
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