中考物理基础知识（十二）:第十八章 电功率

Basic Physics Knowledge for Senior High School Entrance Exam (12): Chapter 18 Electric Power

李宏 湖北省十堰市郧阳中学

Li Hong Yunyang High School, Shiyan City, Hubei Province

第十八章 电功率-[中考物理基础知识]

Chapter 18: Electric Power [Basic Knowledge of Physics for the High School Entrance Exam]

106．电功：电流所做的功叫电功。电功的符号是W。公式：W=UIt

Electric Work:

The work done by an electric current is called electric work, denoted by the symbol W.

Formula:W=UIt W=UIt

电流做功的过程，实际上就是电能转化为其他形式能的过程(例如：光能、热能、机械能)。

The process of electric current doing work is essentially the conversion of electrical energy into other forms of energy (e.g., light, heat, mechanical energy).

电功的单位：焦耳（焦，J）。电功的常用单位是度，即千瓦时（kW·h）。

Units of electric work:SI unit: joule (J)

107．电能表：1kw﹒h＝3．6×10-6J

Electric Energy Meter:

(Note: The original Chinese text contains a typo—“3.6×10⁻⁶J” should be “3.6×10⁶J”. This correction is applied here.)

108．电功率定义式：P=W/t；电功率计算式：P=UI

Electric Power:Definition: P=W/t ;Calculation formula (for DC circuits): P=UI

109．额定功率：用电器在额定电压下的功率。实际功率：用电器在实际电压下的功率。

Rated Power vs. Actual Power:

Rated power: The power consumed by an electrical appliance when operating at its rated voltage.

Actual power: The power consumed when the appliance operates at its actual (applied) voltage.

110．测小灯泡的实际功率：

Measuring the Actual Power of a Small Light Bulb:

（1）原理：P=UI

Principle: P=UI

（2）电路图与伏安法测小灯泡电阻的电路图相同。

Circuit diagram: Same as that used in the volt-ampere method for measuring resistance.

（3）多次测量求出不同电压下的实际功率。

Take multiple measurements to determine the actual power at different voltages.

111．电功率与欧姆定律的推导公式：P=I²R=U²/R

Derived Formulas for Electric Power and Ohm's Law:P=I²R=U²/R

由欧姆定律(From Ohm's Law) U=IR ，代入功率公式(Substituting into the power formula ) P=UI，可得：P=UI=(IR)⋅I=I2R ；同理(Similarly, substituting )，将 I=U/R 代入功率公式：P=UI=U⋅U/R = RU 2

112．焦耳定律：电流通过导体产生的热量跟电流的二次方成正比，跟导体的电阻成正比，跟通电时间成正比。 公式：Q=I²Rt。

Joule's Law: The heat generated by an electric current passing through a conductor is directly proportional to the square of the current, directly proportional to the resistance of the conductor, and directly proportional to the time the current flows. Formula: Q=I²Rt

Explorer of Innovative Thinking

Author: Li Hong

Yunyang High School, Shiyan City, Hubei Province

February 9, 2026