Electrical Power and Energy
Physics ⇒ Electricity and Magnetism
Electrical Power and Energy starts at 8 and continues till grade 12.
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Describe how the efficiency of an electrical device can be calculated using power input and power output.
Describe the difference between electrical power and electrical energy.
Explain why electrical energy is often measured in kilowatt-hours rather than joules for household consumption.
Explain why high-voltage transmission lines are used to reduce energy loss during electricity transmission.
A 100 W lamp is switched on for 10 hours. How much energy does it use in joules?
A 1200 W microwave oven is used for 30 minutes each day for 10 days. How much energy does it consume in kWh?
A 2000 W electric kettle is used for 15 minutes. Calculate the energy consumed in kilowatt-hours.
A 240 V electric iron draws a current of 5 A. Calculate its power rating.
Which of the following appliances uses the most electrical energy if all are used for 2 hours? (1) 100 W fan (2) 60 W bulb (3) 150 W heater (4) 75 W TV
Which of the following best describes the kilowatt-hour? (1) A unit of power (2) A unit of energy (3) A unit of current (4) A unit of voltage
Which of the following is NOT a unit of power? (1) Watt (2) Joule/second (3) Kilowatt (4) Ampere
Which of the following is the correct formula for electrical power? (1) P = V/I (2) P = V × I (3) P = I/V (4) P = V + I
Fill in the blank: 1 kilowatt-hour (kWh) is equal to __________ joules.
Fill in the blank: The cost of electrical energy used in homes is usually calculated based on the number of __________ consumed.
Fill in the blank: The energy transferred by a 100 W device in 1 second is __________ joules.
Fill in the blank: The power rating of an appliance indicates the __________ rate at which it consumes energy.
True or False: Power is a scalar quantity.
True or False: The energy consumed by a device is directly proportional to the time it is used.
True or False: The energy consumed by an appliance depends only on its power rating.
True or False: The power dissipated in a resistor increases if the current through it increases.
