Question

A resistance col of $60\Omega$ is immersed in 42 kg of water. What is the rise in temperature of water per minute if a steady current of 7 A is made to flow through the coli?

• A. 10.10${}^{o}C$
• B. 9.51${}^{o}C$
• C. 1.0${}^{o}C$
• D. 0.5${}^{o}C$

Answer 1

The correct option is C 1.0${}^{o}C$

Given : $R=60\Omega$ $m=42$ kg $I=7$ A $S=4200$ $J/kg{.}^{o}C$ $t=60$ s

Using $\frac{H}{t}=mS\frac{\Delta T}{t}$ where $H=I^{2}Rt$

$\therefore$ $I^{2}R=mS\frac{\Delta T}{t}$

$\therefore$ $7^2\left(60\right)=42\times 4200\frac{\Delta T}{60}$ $⟹\Delta T={1.0}^{o}C$