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標題:
PHY...(electromagnetism)
發問:
1]The primary and secondary coils of an ideal step-down transformer have 2000turns and 50 turns respectively . The primary coil is connected to the 220V main supply while a light bulb is connected to the secondary coil. If the resistance of light bulb is 400 ohm , what will be the current delivered by the... 顯示更多 1] The primary and secondary coils of an ideal step-down transformer have 2000turns and 50 turns respectively . The primary coil is connected to the 220V main supply while a light bulb is connected to the secondary coil. If the resistance of light bulb is 400 ohm , what will be the current delivered by the mains? 2] The primary coil of a step-down transformer is connected to a 220V mains supply. A '6V,12W' light bulb is connected to the secondary coil and it is working at its rated power . If the current in the primary coil is 60mA , what is the efficiency of the transformer?
最佳解答:
1. Voltage at the secondary coil = 220 x (50/2000) v = 5.5 v Power delivered by the secondary coil = 5.5^2/400 w = 0.0756 w Assume 100% efficiency of the transformer, power input at primary coil = 0.0756 w Hence, current at primary coil = 0.0756/220 A = 3.4 x 10^-4 A = 0.34 mA 2. Power input to the transformer = 220 x 60/1000 w = 13.2 w Since power output from the transformer = 12 w efficiency of transformer = 12/13.2 x 100% = 91%
PHY...(electromagnetism)
發問:
1]The primary and secondary coils of an ideal step-down transformer have 2000turns and 50 turns respectively . The primary coil is connected to the 220V main supply while a light bulb is connected to the secondary coil. If the resistance of light bulb is 400 ohm , what will be the current delivered by the... 顯示更多 1] The primary and secondary coils of an ideal step-down transformer have 2000turns and 50 turns respectively . The primary coil is connected to the 220V main supply while a light bulb is connected to the secondary coil. If the resistance of light bulb is 400 ohm , what will be the current delivered by the mains? 2] The primary coil of a step-down transformer is connected to a 220V mains supply. A '6V,12W' light bulb is connected to the secondary coil and it is working at its rated power . If the current in the primary coil is 60mA , what is the efficiency of the transformer?
最佳解答:
1. Voltage at the secondary coil = 220 x (50/2000) v = 5.5 v Power delivered by the secondary coil = 5.5^2/400 w = 0.0756 w Assume 100% efficiency of the transformer, power input at primary coil = 0.0756 w Hence, current at primary coil = 0.0756/220 A = 3.4 x 10^-4 A = 0.34 mA 2. Power input to the transformer = 220 x 60/1000 w = 13.2 w Since power output from the transformer = 12 w efficiency of transformer = 12/13.2 x 100% = 91%
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