The e.m.f. of an Edison cell, when fully charged, is nearly

1.4 V
1 V
0.9 V
0.8 V

The correct answer is A. 1.4 V.

An Edison cell is a primary cell that uses a zinc anode and a manganese dioxide cathode. The electrolyte is a mixture of ammonium chloride and zinc chloride. The cell produces a voltage of about 1.4 volts when fully charged.

Option B is incorrect because the voltage of an Edison cell is about 1.4 volts, not 1 volt.

Option C is incorrect because the voltage of an Edison cell is about 1.4 volts, not 0.9 volts.

Option D is incorrect because the voltage of an Edison cell is about 1.4 volts, not 0.8 volts.