1.7.3. Energy resources
A subsection of Physics, 5054, through 1. Motion, forces and energy
Listing 10 of 46 questions
shows a hydroelectric power station. Water from the lake is used to produce electricity in the turbine house. State where the water in has the least potential energy. In 30 minutes, the water loses 5.0 × 109J of energy and 4.5 × 109J of electrical energy is produced in the turbine house. Calculate the efficiency of the energy conversion. efficiency = Calculate, in watts, the electrical power output from the turbine house. power = W Some power stations burn coal to produce the same electrical power output. State one advantage of the hydroelectric power station. State one harmful effect that the hydroelectric power station may have on the environment. to river turbine house dam lake Use
5054_s05_qp_2
THEORY
2005
Paper 2, Variant 0
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Wind energy is a renewable energy source. A wind turbine and generator convert energy in the wind to electrical energy in a generator. shows some wind turbines. State what is meant by a renewable energy source. State the name of one other renewable energy source. Some methods of generating electricity cause much more global warming than wind energy. 1. State one method of generating electricity that causes a large amount of global warming. 2. Describe, in outline, how the method you have chosen causes a significant amount of global warming. During a 30 minute period, a mass of 4.2 × 107 kg of air enters the turbine with a speed of 15 m / s. Calculate the kinetic energy of the air that enters the turbine in 30 minutes. energy = The electrical power output of the generator connected to the turbine is 8.4 × 105 W. Calculate the electrical energy output from the turbine in 30 minutes. energy output = Calculate the efficiency of the turbine and generator in converting the kinetic energy of the air to electrical energy. efficiency = The generator contains a coil that rotates between the poles of a magnet. The coil rotates 50 times in one second and produces an alternating voltage output with a maximum value of 500 V. On the grid in , sketch a voltage−time graph showing the output voltage. 0.01 –500 voltage / V 0.02 0.03 time / s The output voltage from the generator is stepped up by a transformer. The electrical energy then passes along a transmission line to a distant house. Explain why 1. a high voltage is used for the transmission of electrical energy, 2. a transformer is used to connect the transmission line to the house.
5054_s18_qp_22
THEORY
2018
Paper 2, Variant 2
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Some sources of energy, used to produce electricity, may run out in the future. Underline the two sources of energy that are likely to run out first, before the others. coal oil solar tides wave wind is a simplified diagram of a geothermal power station. steam turbine generator steam cooling tower water Thermal energy is given to the water as it passes through rocks underground. Describe the process by which this thermal energy causes the turbine to turn. Water from the cooling tower at 30 °C passes into the ground and is heated to 160 °C. The specific heat capacity of water is 4200 J / (kg °C). Calculate the thermal energy needed to heat 90 kg of water from 30 °C to 160 °C. thermal energy =
5054_s19_qp_21
THEORY
2019
Paper 2, Variant 1
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Questions Discovered
46