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 a fuse is rated in amperes and not in watts.
Explain why electrical transmission lines are operated at high voltages to reduce energy loss.
A household uses 500 kWh of energy in a month. If the cost per kWh is $0.20, what is the total cost for the month?
Which of the following appliances uses the most electrical energy if all are operated for 2 hours?
(1) 60 W fan
(2) 100 W bulb
(3) 150 W heater
(4) 75 W television
Which of the following best describes the relationship between current, voltage, and power in a circuit?
(1) Power increases as current increases, if voltage is constant.
(2) Power decreases as current increases, if voltage is constant.
(3) Power is independent of current.
(4) Power is independent of voltage.
Which of the following is NOT a correct unit for power?
(1) Watt
(2) Joule per second
(3) Kilowatt
(4) Joule
Which of the following is the correct formula for electrical power in terms of voltage (V) and current (I)?
(1) P = V/I
(2) P = V × I
(3) P = I/V
(4) P = V + I
Fill in the blank: The cost of electrical energy consumed is calculated by multiplying the number of __________ used by the cost per unit.
Fill in the blank: The energy consumed by a device is equal to the product of its power and __________.
Fill in the blank: The energy transferred by an electric current of 1 ampere flowing for 1 second through a potential difference of 1 volt is __________ joule(s).
Fill in the blank: The power dissipated in a resistor can also be calculated using the formula P = __________, where R is resistance and I is current.
True or False: Power can be expressed as P = V²/R for a resistor.
True or False: Reducing the resistance in a circuit while keeping voltage constant will increase the power consumed.
True or False: The joule (J) is the SI unit of electrical energy.
True or False: The power rating of an appliance indicates the maximum power it can safely use.
