4.4.1. Uses of electricity
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 84 questions
shows the dam and reservoir of a hydroelectric power station. A hydroelectric power station uses a renewable energy source. State two other renewable energy sources. 1. 2. When the power station operates at full capacity, the electrical power output is 6.8 × 109 W. 1. Calculate the electrical energy output of the power station if it operates at full capacity for one year. energy = 2. Suggest why, in practice, the power station does not operate at full capacity throughout the year. The water surface in the reservoir that supplies the hydroelectric power station is at a vertical height of 170 m above the turbines. In one hour, 1.6 × 1010 kg of water flows from the reservoir through the turbines. The gravitational field strength g is 10 N / kg. 1. Calculate the gravitational potential energy that is converted into other forms of energy in one hour. energy = 2. Calculate the efficiency of the power station when operating at full capacity. efficiency = 3. Suggest two reasons why the efficiency of the power station is less than 1.0 (100%). 1. 2. Before the electrical energy is transmitted along power lines, the voltage is increased to a very large value. State and explain why a very high voltage is used to transmit electrical energy over long distances. State the name of the device that is used to increase the voltage. Explain why the generators in the power station must be a.c. (alternating current) generators.
5054_w14_qp_21
THEORY
2014
Paper 2, Variant 1
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A spotlight in a television studio is at full brightness. The lamp inside the spotlight is powered by a 230 V supply and the current in the filament of the lamp is 27 A. Calculate the power of the lamp. power = The spotlight is kept switched on at full brightness. Calculate the energy transformed by the lamp in 30 minutes. energy = The cost of using one kilowatt-hour (kWh) of electricity is 23 cents. Calculate the cost of using the spotlight for 30 minutes. cost =
5054_w15_qp_22
THEORY
2015
Paper 2, Variant 2
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A 75 W filament lamp in an office is accidentally left switched on for 63 hours when the office is closed. Calculate the electrical energy that is supplied to this lamp in this time. electrical energy = The efficiency of the lamp is 0.12 (12%). Calculate the energy released by the lamp in the form of light. light energy = The power station that generates the electricity supplied to the office uses oil as its fuel. State and explain whether oil is a renewable or a non-renewable source of energy. Discuss one environmental consequence of using oil as a source of energy.
5054_w17_qp_22
THEORY
2017
Paper 2, Variant 2
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Questions Discovered
84