(免费!)物理电功率总复习(精心整理)(国外英文资料).doc

(免费!)物理电功率总复习(精心整理)(国外英文资料) General review of electrical power Knowledge network Heavy and difficult focus (1) electric power 1., three physical quantities Electrical energy (W): the unit of international system is the Joule (J), the common unit is kilowatt hour (kW. H), commonly known as the degree, 1 degrees =1kW h= Electric power (P): the work done by electric current in unit time. It is the physical quantity that represents the speed of the current. The unit of international system is Watt (W), and the common unit is kW (kW). Electrothermal (Q): the heat produced by electric current passing through a conductor. The unit of international system is the Joule (J). 2., two important experiments Measure the electric power of a small bulb measuring principle circuit design Operation procedure Matters needing attention： When the A. is connected, the switch is switched off to prevent damage to the power or bulb due to a short circuit. Before the B. switch is closed, the slider of the sliding rheostat shall slide to the maximum resistance of the sliding rheostat to prevent the current in the circuit from too large and to burn out the lamp. C. the power supply voltage shall be higher than the rated voltage of the bulb to prevent the voltage from being adjusted to the rated voltage. The range of the D. voltmeter shall be greater than the rated voltage of the bulb, and the range of the ammeter shall be greater than the current at the normal operation of the bulb. E. sliding rheostat allows the maximum current to be greater than the current of the bulb when working normally. The maximum resistance value of the sliding rheostat should be approximately the same as that of the bulb, so that the adjustment effect is obvious. F. through three different voltage (rated voltage, rated voltage and 1.2 times lower than the rated voltage) measurements, with the actual experience of electrical power is not necessarily equal to the rated power, but depends on the actual voltage in the us