Question

An iron-copper thermo couple is connected to an external battery of e.m.f. E. On doubling the emf of the battery, the heat produced at a junction:

• A. remains same
• B. becomes half
• C. is doubled
• D. becomes four times

Answer 1

The correct option is D becomes four times

As $Q\propto \frac{v^2}{r}$
r is not changed only E.M.F. is doubled.
$v\Rightarrow 2v\equiv Q\Rightarrow 2^{2}Q=4Q$