In this device the Gibbs energy of the spontaneous
redox reaction is converted into electrical work which may be used for
running a motor or other electrical gadgets  like heater, fan,
geyser, etc Daniell cell discussed earlier is one such cell in which the following
redox reaction occurs Zn(s) + Cu2+(aq) ® Zn2+ (aq) + Cu(s)
This reaction is a combination of two half reactions whose addition
gives the overall cell reaction:
(i) Cu2+   +  2e–    ® Cu(s)
(reduction half reaction)
(2 2)
(ii) Zn(s)  ® Zn2+ + 2e–
(oxidation half reaction)
(2