Which of the following is an incorrect expression for electrical power in a circuit?

𝐼𝑅² the term does not represent electrical power in a circuit. 

Explanation: 

● Power is the rate of electrical energy transfer by an electrical circuit per unit of time. 

● It is denoted by 𝑃, and the 𝑆𝐼 unit is one joule per second or watt. 

The formula used for electric power is 

𝑃 = 𝑉𝐼 −−−−−−−− (1) 

where 𝑃 = Electric power, 𝑉 = Potential difference in the circuit, 𝐼 = current 

We know from ohm's law 

𝑉 = 𝐼𝑅 

Substitute 𝑉 = 𝐼𝑅 in (1) we get, 

𝑃 = (𝐼𝑅)𝐼 

⇒ 𝑃 = 𝐼²𝑅 −−−−− (2) 

Again, From ohm’s law 

𝐼 = 𝑉/𝑅 −−−−−−−−−−− (3) 

Substituting equation (3) in equation (1), we get 

𝑃 = 𝑉² /𝑅 −−−−−−−−−− (4)

∴Equation (1), (2) and (4) represents electric power, whereas 𝐼𝑅² does not represent electric power. 

Hence option (b) 𝐼𝑅² is correct