Problem

[qim]

"When applied for a few minutes after a potential difference is applied, it is observed that the current through the specimen increases substantially although the applied potential difference remains constant. Explain why the current should increase in this way."

Could I be correct in thinking that the question refers to the case of, say, two electrodes dipped in a solution of sulphuric acid, where a certain voltage across the electrodes needs to be present before any current will flow?

Any help appreciated.

qim

[jamesrc]

Sure, but wouldn't any capacitor do just as well?

[gnome]

If the only element in the circuit is a capacitor, wouldn't the current be at a maximum when the voltage is first applied, and soon decrease to zero once the capacitor is fully charged?

I think you're looking at an inductor instead. The back emf would be at a maximum when the current starts flowing, decreasing exponentially toward zero as the current increases to Imax.

[jamesrc]

Whoops. That's what I meant. [:)]

I'm always getting things backwards.

[gnome]

Not always. We all have our moments. [:D]