Water is heated with a coil of resistance R connected to domestic supply. The rise of temperature of the 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 :

The rise in temperature of water heated by a coil depends on the total heat energy produced, which is governed by Joule's law of heating. According to this law, the heat produced (H) in a resistor is directly proportional to the square of the current (I), the resistance (R), and the time (t) for which the current flows, expressed as H = I²Rt [2]. In a domestic supply, the current passing through the coil is determined by Ohm's law (I = V/R), where V is the supply voltage [1]. Consequently, the heat energy can also be expressed as H = (V²/R)t. Since the temperature rise (ΔT) is proportional to the total energy supplied (ΔT = H/mc), it depends on the supply voltage (V), the current (I), and the duration of heating (t) [1][2]. Thus, all three factors—supply voltage, current, and time—are critical determinants of the temperature rise.

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > H = I2 > p. 189
2. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192