What is the equation linking power and cost?

What is the equation linking power and cost?

• A. Power x time x cost per unit
• B. Power x cost per unit
• C. Energy x price
• D. Voltage x current x cost

Answer: (A)

Cost depends on how much energy you use and the price of that energy. Energy used equals power times time, so the total cost is energy times the price per unit of energy. Put together: cost = (power × time) × price per unit energy. This makes sense in practical terms: a device with a certain power draws that much energy for the duration it runs, and you pay a price for each unit of energy consumed. That’s why this option is the best one: it explicitly includes power, the duration of use, and the price per energy unit to give the total cost. If you only multiply power by price, you’d be missing the time factor. If you use voltage × current, you get power but still need time to convert to energy. And while you could compute cost as energy × price, you first need to know the energy, which comes from power and time.

Cost depends on how much energy you use and the price of that energy. Energy used equals power times time, so the total cost is energy times the price per unit of energy. Put together: cost = (power × time) × price per unit energy. This makes sense in practical terms: a device with a certain power draws that much energy for the duration it runs, and you pay a price for each unit of energy consumed.

That’s why this option is the best one: it explicitly includes power, the duration of use, and the price per energy unit to give the total cost. If you only multiply power by price, you’d be missing the time factor. If you use voltage × current, you get power but still need time to convert to energy. And while you could compute cost as energy × price, you first need to know the energy, which comes from power and time.