實(shí)驗(yàn)證明當(dāng)電流過導(dǎo)體時(shí)，由于自由電子的碰撞，導(dǎo)體的溫度會(huì)升高。這是因?yàn)閷?dǎo)體吸收的點(diǎn)電能轉(zhuǎn)換成為熱能的緣故。這種現(xiàn)象叫做電流的熱效應(yīng)。電流通過導(dǎo)體時(shí)所產(chǎn)生的熱量與電流強(qiáng)度的平方、導(dǎo)體本身的電阻、以及電流通過的時(shí)間成正比。這一結(jié)論稱為焦耳——楞次定律，其數(shù)學(xué)表達(dá)式為：Q=I²Rt，公式中：
Experiments show that when a current is over a conductor, the temperature of the conductor increases because of the collision of free electrons. This is because the electrical energy absorbed by the conductor is converted into thermal energy. This phenomenon is called the thermal effect of the current. The heat generated by a current through a conductor is proportional to the square of the current intensity, the resistance of the conductor itself, and the time passed by the current. This conclusion is called Joule - Lenz's law, the mathematical expression of Q=I - Rt in the formula:
Q：電流通過導(dǎo)體所產(chǎn)生的熱量，單位：焦耳（J）；
Q: the heat generated by a current through a conductor, unit: Joule (J);
I：通過導(dǎo)體的電流，單位：安（A）；
I: through the current of the conductor, unit: an (A);
R：導(dǎo)體的電阻，單位：歐（Ω）
R: the resistance of a conductor, unit: Europe (omega)
如果熱量以卡位單位，則Q=I?Rt公式可寫成：Q=0.24I²Rt=0.24Pt，此公式稱為焦耳-楞次定律。其中t的單位為妙，R的單位是歐，I的單位是安，熱量的單位是卡。JFEM電機(jī)引接線電流的熱效應(yīng)
If the heat in card unit, Q=I? Rt equation can be written as: Q=0.24I - Rt=0.24Pt, this formula is called the Joule Lenz. The unit of T is wonderful, the unit of R is Europe, and the unit of I is Ann, and the unit of heat is card.
電流的熱效應(yīng)在生產(chǎn)上有許多應(yīng)用。電燈是利用電流產(chǎn)生的熱使得燈絲達(dá)到白熾狀態(tài)而發(fā)光，熔斷器是利用電流產(chǎn)生的熱使其熔斷而切斷電源。電流的熱效應(yīng)也是近代工業(yè)中的一種重要加熱方式，如利用電爐煉鋼，電機(jī)通電烘干等。電流的熱效應(yīng)也有它不利的一面，由于構(gòu)成電氣設(shè)備的導(dǎo)線存在電阻，所有電氣設(shè)備在工作時(shí)要發(fā)熱，使溫度升高。如果電流過大，溫度升高多就會(huì)加速絕緣體老化，甚至損壞設(shè)備。為了保證電氣設(shè)備能正常工作，各種設(shè)備都規(guī)定了限額，如額定電流、額定電壓、和額定電功率等。JFEM電機(jī)引接線電流的熱效應(yīng)
The thermal effect of current has many applications in production. The electric lamp is the heat produced by the current that makes the filament light up in the incandescent state, and the fuse uses the heat generated by the current to break it off and cut off the power. The thermal effect of current is also an important heating mode in modern industry, such as the use of electric furnace steelmaking, electric motor drying and so on. The thermal effect of electric current also has its disadvantage. Because there are resistances in electrical conductors that make up electrical equipment, all electrical equipments must be heated when they are working, so that the temperature will increase. If the current is too large, the increase of temperature will accelerate the aging of the insulator and even damage the equipment. In order to ensure the normal work of electrical equipment, all kinds of equipment are prescribed limits, such as rated current, rated voltage, and rated electric power.
電器設(shè)備的額定值通常用下標(biāo)“e”表示，如Ie、Ue、Pe等，各種電器設(shè)備的銘牌上都有標(biāo)注他們的數(shù)值。
The rated value of electrical equipment is usually expressed as "e", such as Ie, Ue, Pe and so on. All kinds of electrical equipment nameplates are marked with their values.