Power and Energy

Subject: Electrical Technology (Test)
Date: June 26, 2010
Grade: Ten (10)
Topic: Power and Energy (A2.8)

Instruction: Answer ALL the questions below.

1. Define the following and state the symbol(s) and Unit(s) of each:
    a. Energy
    b. Power
    c. Voltage
    d. Current 
    e. Resistance
    f. Time
                                                                                                                                                     [12 marks]

2. A 3-phase ac motor is rated at 3kW, 220V is used to drive a pulley system. Calculate the horsepower rating of the motor?
                                                                                                                                                      [3 marks]

3. Two lamps rated 100W, 120V and 75W, 120V are connected in a series circuit across a 120V supply. Calculate the following:
  a. The resistance of each lamp
  b. The current flowing through the circuit
  c. The total power dissipated by both lamps
  d. The energy used by the lamps in kWh, if the circuit is switched-on for 30 minutes.
                                                                                                                                                     [10 marks]

4. Calculate the following energy bill given the previous reading as 74653 kWh and $400 was brought forward from the last bill. Follow the following steps to complete the energy bill: Previous Reading, Current Reading, Reading for the month, Energy first, Energy Next, Fuel/Ipp, Tax 17.5% and the Total.     
                                                                                                                                                     [10 marks]