In a DC circuit, the power equation is given by which expression?

In a DC circuit, the power equation is given by which expression?

• A. P = E x I
• B. P = V x I
• C. P = E / I
• D. P = I^2 x R

Answer: (A)

Power in a DC circuit equals the product of voltage and current. If the source voltage is denoted by E (the emf), the power delivered is P = E × I. This is the same relationship as P = V × I, just using E for voltage. The other forms aren’t universal: P = I^2 × R applies specifically to a resistor with resistance R (derived from V = IR), and P = E / I would give units of resistance, not watts, so it doesn’t describe power.

Power in a DC circuit equals the product of voltage and current. If the source voltage is denoted by E (the emf), the power delivered is P = E × I. This is the same relationship as P = V × I, just using E for voltage. The other forms aren’t universal: P = I^2 × R applies specifically to a resistor with resistance R (derived from V = IR), and P = E / I would give units of resistance, not watts, so it doesn’t describe power.