This physics problem tests your understanding of fundamental physical laws and their applications. The step-by-step solution below breaks down the problem using relevant equations and physical reasoning.
ScanSolve AI Answer
Here are the solutions to your questions: 1. Explain why kilowatt hour is a unit of energy not power. A kilowatt hour (kWh) is a unit of energy because it represents the product of power (kilowatt) and time (hour). Energy is defined as the capacity to do work, and it is calculated by multiplying the rate at which work is done (power) by the duration over which it is done (time). Power, on the other hand, is the rate of energy transfer or consumption, measured in watts or kilowatts. 2. In the following questions, use a tariff of R1.50 per kilowatt hour (including VAT). a) Four 15\, W energy saving bulbs are switched on for 5\, hours in the evening. Calculate cost (R). Step 1: Calculate the total power of the bulbs. Total Power = 4\, bulbs × 15\, W/bulb = 60\, W Step 2: Convert the total power from watts to kilowatts. Total Power = 60\, W × 1\, kW1000\, W = 0.060\, kW Step 3: Calculate the total energy consumed in kilowatt hours. Energy = Power × Time Energy = 0.060\, kW × 5\, hours = 0.30\, kWh Step 4: Calculate the total cost. Cost = Energy × Tariff Cost = 0.30\, kWh × R1.50/kWh = R0.45 The cost is R0.45. b) Calculate the cost of using a 100\, W heater for 3\, hours and 30\, min. Step 1: Convert the power from watts to kilowatts. Power = 100\, W × 1\, kW1000\, W = 0.100\, kW Step 2: Convert the total time to hours. Time = 3\, hours + 30\, min × 1\, hour60\, min Time = 3\, hours + 0.5\, hours = 3.5\, hours Step 3: Calculate the total energy consumed in kilowatt hours. Energy = Power × Time Energy = 0.100\, kW × 3.5\, hours = 0.35\, kWh Step 4: Calculate the total cost. Cost = Energy × Tariff Cost = 0.35\, kWh × R1.50/kWh = R0.525 The cost is R0.53. 3 done, 2 left today. You're making progress.