Water is heated with a coil of resistance R connected to domestic supply. The rise of temperature of water will depend on
1. Supply voltage.
2. Current passing through the coil.
3. Time for which voltage is supplied.
Select the correct answer from among the following :
[amp_mcq option1=”1, 2 and 3″ option2=”1 and 2 only” option3=”1 only” option4=”2 and 3 only” correct=”option1″]
This question was previously asked in
UPSC NDA-2 – 2019
The correct answer is A) 1, 2 and 3.
When a resistance coil is connected to a domestic supply, it generates heat according to Joule’s law of heating. The heat produced (H) is given by $H = I^2 R t$, where I is the current, R is the resistance, and t is the time. Using Ohm’s law ($V = IR$), this can also be expressed as $H = \frac{V^2}{R} t$ or $H = V I t$. The rise in temperature of the water is proportional to the heat supplied to it. Therefore, the rise in temperature depends on the supply voltage (V), the current passing through the coil (I), and the time for which the voltage is supplied (t). All three factors influence the amount of heat generated and transferred to the water.