Question

Suppose that an alkaline dry cell was manufactured using cadmium metal rather than zinc. What happens to emf?

• A. There will be no change in emf.
• B. The voltage would increase.
• C. The voltage would decrease.
• D. The setup will not work.

Answer 1

The correct option is C The voltage would decrease.

We usually use zinc metal in alkaline dry cell. The zinc metal acts as negative terminal of the cell. If we replace zinc metal with cadmium, then cadmium acts as negative metal. But because of lower reactivity of cadmium compared to zinc, cadmium will release less electrons in the dry electrolyte. Less charges released in the electrolyte will result in lower difference of potential between the positive and negative electrodes in the cell. Therefore the new potential difference offered by this dry cell will decrease to 1.64 volts from 2 volts.