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Q82 (NDA-II/2022) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism

Which one of the following terms cannot represent electrical power in a circuit?

Result
Your answer: —  Â·  Correct: B
Explanation

Electrical power (P) is defined as the rate at which electrical energy is dissipated or consumed in a circuit [2]. The fundamental expression for power is P = VI, where V is potential difference and I is current [1][2]. By applying Ohm's law (V = IR), alternative expressions for power in resistive circuits can be derived [3]. Substituting V = IR into the power formula yields P = (IR)I = I²R [2]. Alternatively, substituting I = V/R into the formula yields P = V(V/R) = V²/R [2]. These three expressions—VI, I²R, and V²/R—are standard representations of electrical power [1]. The term I²/R is mathematically incorrect and does not represent power, as it does not align with the derivation from Ohm's law or Joule's law of heating. Therefore, I²/R is the term that cannot represent electrical power.

Sources

  1. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.8 ELECTRIC POWER > p. 191
  2. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192
  3. [3] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > Figure 11.3 > p. 176
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