A potentiometer wire has a gradient of 2.5 mV/cm…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A potentiometer wire has a gradient of . A cell balances at when open. A resistor is then joined across the cell, and the balance point moves to . Find the emf and the internal resistance of the cell, and the current through the resistor.
Need a reminder? The key ideaShow
The gradient is , and the potential at a distance is . At balance , so . A balance with the cell open and with across it gives . A voltmeter of resistance across a cell reads .
The worked solution
Have you tried it?
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 emf. .
Step 2. The internal resistance. .
Step 3. The current. .
Check. The terminal voltage is , and .
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