小功率電阻器通常為封裝在塑料外殼中的碳膜構(gòu)成，而大功率的電阻器通常為繞線電阻器，通過將大電阻率的金屬絲繞在瓷心上而制成。
如果一個(gè)電阻器的電阻值接近零歐姆（例如，兩個(gè)點(diǎn)之間的大截面導(dǎo)線），則該電阻器對(duì)電流沒有阻礙作用，并聯(lián)這種電阻器的回路被短路，電流無(wú)限大。如果一個(gè)電阻器具有無(wú)限大的或很大的電阻，則串接該電阻器的回路可看作開路，電流為零。工業(yè)中常用的電阻器介于兩種情況之間，它具有一定的電阻，可通過一定的電流，但電流不像短路時(shí)那樣大。電阻器的限流作用類似于接在兩根大直徑管子之間的小直徑管子限制水流量的作用。電阻，英文名resistance，通?？s寫為R，它是導(dǎo)體的一種基本性質(zhì)，與導(dǎo)體的尺寸、材料、溫度有關(guān)。歐姆定律說，I=U/R，那么R=U/I，電阻的基本單位是歐姆，用希臘字母“Ω”表示，有這樣的定義：導(dǎo)體上加上一伏特電壓時(shí)，產(chǎn)生一安培電流所對(duì)應(yīng)的阻值。電阻的主要職能就是阻礙電流流過。事實(shí)上，“電阻”說的是一種性質(zhì)，而通常在電子產(chǎn)品中所指的電阻，是指電阻器這樣一種元件。歐姆常簡(jiǎn)稱為歐。表示電阻阻值的常用單位還有千歐（kΩ），兆歐（MΩ），毫歐（m Ω）。

Low power resistors are usually made of carbon film encapsulated in a plastic shell, while high-power resistors are usually wound resistors, which are made by winding metal wires with high resistivity around the porcelain core.
If the resistance value of a resistor is close to zero ohms (for example, a large cross-section wire between two points), the resistor has no blocking effect on the current. The circuit in parallel with this resistor is short circuited and the current is infinite. If a resistor has infinite or large resistance, the circuit connected in series with the resistor can be regarded as an open circuit with zero current. The resistor commonly used in industry is between the two extreme cases. It has a certain resistance and can pass a certain current, but the current is not as large as when it is short circuited. The current limiting effect of the resistor is similar to that of the small-diameter pipe connected between two large-diameter pipes to limit the water flow. Resistance, the English name of resistance, usually abbreviated as R, is a basic property of conductor, which is related to the size, material and temperature of conductor. Ohm's law says that i=u/r, then r=u/i, the basic unit of resistance is Ohm, which is represented by the Greek letter "Ω". There is such a definition: when a voltage of one volt is added to a conductor, the resistance corresponding to one ampere current is generated. The main function of resistance is to block the flow of current. In fact, "resistance" refers to a kind of property, and the resistance usually referred to in electronic products refers to such an element as a resistor. Ohm is often abbreviated as ohm. The commonly used units of resistance are kilo ohm (K Ω), megaohm (m Ω), and milliohm (m Ω)