Which expression correctly represents voltage when power and current are known?

• A. V = P * I
• B. V = I / P
• C. V = P / I
• D. V = R * I

Answer: (C)

Understanding the relationship between power, voltage, and current is key. In electrical terms, power equals voltage times current (P = V × I). If you know power and current, solve for voltage by dividing power by current, giving V = P / I. This makes sense unit-wise since watts (P) divided by amperes (I) yields volts (W/A = V). For example, if P = 60 W and I = 2 A, V = 60 / 2 = 30 V. The other expressions don’t reflect the P = V × I relationship: multiplying P by I would give an incorrect result, and V = I / P has incorrect units; V = I R is Ohm’s law using resistance, not a form that expresses voltage in terms of known power and current.