The answer you are looking for is 400 joules.
Explanation:
i1=1ampere
i1+i2=I
VA−VB=i1×3Ω=i2×6
⇒1×3=i2×6
2i=21ampere
Hence I=i1+i2=1+0.5=1.5ampere
Req=2+3+63×6=2+93×6=4Ω
equivalent circuit
Refer image .2
From KVL
1req=v
v=1.5×4
C. Combustion reaction.
These reaction are exothermic.
The reactions are:
2Mg + O2 -----> 2MgO
3Mg + N2 ------> Mg3N2
D. Only B and C
Medium and High levels can be harmful. But low even levels aren't good either.
When the ion concentrations in the cathode half-cell are increased by a factor of 10, the change in the cell voltage is ln10 times greater. This comes from the Nernst equation. Use variation to solve for the cell voltage in terms of the initial cell voltage before increasing the ion concentrations by 10.