Electromagnetic Induction Watt -Hour Meter Watt hour meter is a device that is used to measure electrical energy. Electrical energy is measured using the unit kilowatt hour. This is also known as a unit. 1 unit electrical energy = 1 kWh The commercial unit of electrical energy is kilowatt hour ( kWh). Watt hour meter A device of power 1000 watt (1 kW), when used for one hour Fig. 3.15 (1h), consumes one unit of electrical energy (1 kWh) The following equation can be used to calculate the electrical energy used. Power in watt × time in hour Energy in kilowatt hour = 1000 • A grinder of power 750 W works for 2 hours. Calculate the energy consumed. Energy = 750 × 2 1500 = 1.5 unit (kWh) 1000 = 1000 • In a house, 5 CF lamps each of 20 W, works for 4 hours, 4 fans each of 60 W work for 5 hours and a TV of 100 W works for 4 hours in a day. What will be the daily consumption shown by the watt hour meter? The tariff instituted by KSEB for household consumers is given in Table 3.8. Analyse this table and explore the various possibilities for energy conservation. Prepare a project to plan the energy consumption at your home to minimise the cost of electricity. You know that electricity is a form of energy that is extremely dangerous. Hence different safety measures are inbuilt in household circuit. (Hence household wiring is done by including so many safety measures) Safety measures in household electrification 1. Safety Fuse In the previous chapter you have studied how a safety fuse protects a circuit. Table 3.8 65
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