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Electrical Energy and Power
The SPM Physics Workbook is developed under the One-School.net Free Books Project. The content of this book is strictly follow Malaysia SPM (Sijil Pelajaran Malaysia) syllabus. The aim of this project is to provide a complete electronic supplementary network for students to develop self-learning skills by breaking the spoon-feed rituals and to encourage them to compile educational information from the Internet.
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1) A current of 0.50A flows through a 100 Ω resistor. Find the power dissipated from the resistor?
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200W |
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50W |
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25W |
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20W |
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2) A bulb rated 240 V, 18 W is operated from a 240V power source. Find the current flowing through the bulb.
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3) 3 light bulbs of resistance 1Ω, 2Ω and 3Ω are connected in series to a power source of 240V. Find the power of the light bulb of resistance 2Ω.
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4)
The figure above shows that an ideal battery is connected in parallel to two resistors with resistances 2 Ω and 4 Ω. Find the power dissipated in the 2 Ω resistor.
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5) Find the total power dissipated in the circuit above.
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6) Find the total power dissipated in the circuit above.
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7) A 2000W heater is used to heat 500 cm3of water.Find the minimum time needed to heat the water from 25 to 100 °C. (Specific Heat Capacity of water = 4200Jkg-1oC-1)
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8) An electric heater of power 3600W is used to heat water for 15 minutes. If the cost of 1 unit (kilowatthour) energy consumption is 24 cent, what is the cost of this heating process?
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9) An electric motor raises a mass of 20kg to a height of 5m in 10s. Given that the electric motor is connected to a power source of 80V and current 2A. Find the efficiency of the motor.
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