| 1. | For the following circuit, calculate all unknown resistor values. (ANS: R1 = 80W, R2 = 50W, R3 = 100W, and R4 = 50W) |
| 2. | A 3hp motor is connected in parallel with a 1250W electric heater. If these devices are connected to a 120V source, what is the total circuit current?(ANS: IT = 29.07A) |
| 3. | A typical residential electric hot water heater can heat 32kg from 50C to 750C in 30 minutes. If this water heater contains two 3000W heating elements connected in parallel to a 220V source, calculate: (a) The water heater efficiency (ANS: 86.8%) (b) The cost to heat the water up if electricity costs 6¢/kWh (ANS: 18¢) |
| 4. | A stove is used to heat up water from 50C to 1000C. The cost to heat the water is 7.2¢, when electricity costs 6.1¢/kWh, and the element is 75% efficient. If the stove heats up the water in 7 minutes, calculate: (a) The power of the element (ANS: 10110W) (b) The mass of the water (ANS: 8kg) |
| 5. | An industrial ARC furnace, which is 60% efficient, can heat an aluminum alloy from 200C to 2200C in 33 minutes. The furnace is connected to a 440V source and draws 10A. If the alloy has a mass of 5kg, calculate: (a) Power required by the ARC furnace (ANS: 4.4kW) (b) The specific heat of the alloy (ANS: 5.23) |
