The potential difference between the terminals of an electrical heating device is 40 V, when it draws a current of 2 A from the source. Which one of the following is the correct value of current drawn by the heating device if the potential is increased to 140 V?

According to Ohm's law, the potential difference (V) across a conductor is directly proportional to the current (I) flowing through it, provided the temperature remains constant [3]. This relationship is expressed as V = IR, where R is the resistance [2]. In the first scenario, the device has a potential difference of 40 V and draws 2 A of current. Using the formula R = V/I, the resistance is calculated as 40 V / 2 A = 20 Ω [1]. Since the resistance of the heating device remains constant, we can calculate the new current when the potential difference is increased to 140 V [3]. Using the rearranged formula I = V/R, the new current is 140 V / 20 Ω = 7 A [1]. Thus, the current drawn by the device at 140 V is 7 A.

Sources

1. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Figure 11.3 > p. 176
2. [3] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
3. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > H = I2 > p. 189