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When an electric heater is connected to a 100V DC power supply and consumes electric power P, if it is connected to a sinusoidal AC power supply and consumes power P / 9 (less than the influence of temperature and resistance), the maximum value of the sinusoidal AC voltage is? I get (100 √ 3) / 3
P = u squared / r because R is constant, so p direct / P intersect = u direct squared / u intersect (effective) squared
Derived 9 = 10000 / u intersection (effective) square derived u intersection (effective) = 100 / 3
Derived u intersection max = 100 √ 3 / 3
When an electric heater is connected to a 10V DC power supply, it can generate a certain amount of thermal power. When it is connected to an AC power supply, the thermal power is half of that of the DC power. If the resistance changes with temperature, the peak value of AC power should be? Please write a brief process
According to the meaning of the question, we can know that p-intersection = 1 / 2p-direct
P = u & # 178 / R (u-ac) & # 178 / r = 1 / 2 * (u-dc) & # 178 / R u-ac = u-dc / √ 2 = 10 / √ 2V
Peak value of AC voltage: √ 2 * u AC = √ 2 * 10 / √ 2 = 10V
When an electric heater is connected to a 100V DC power supply, the heat generated in t time is Q. if it is connected to an AC power supply with U1 = 100sin ω t (V) and U2 = 50sin 2 ω t (V) respectively, the heat still needs to be generated, then the time required is ()
A. t，2tB. t，tC. 2t，2tD. 2t，8t
Let the resistance of the electric heater be r. when the electric heater is connected to the U = 100V DC power supply, q = u2rt. When the electric heater is connected to the AC power supply instead, q = (um12) 2rt ′ = 2T according to um1 = 100V. When the electric heater is connected to the AC power supply instead, q = (um22) 2rt ″ = 8t according to Um2 = 50V
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