欧姆定律
欧姆定律说明了电流和电位降之间的联系。德国科学家乔治·西蒙·欧姆通过实验首次验证了欧姆定律。欧姆定律是电路最基本和必要的定律之一。
欧姆定律指出,只要所有物理条件和温度保持不变,导体上的电压与通过它的流量成正比。
在数学上,这种电流-电压关系通常写成,
V = IR
In the equation, the constant of proportion, R is Resistance and has units of ohms, with symbol Ω.
相同的公式经常被重写来计算电阻:
如果提供的温度和不同的物理因素保持不变,欧姆定律才成立。入库零件,温度升高。与此相关的护理示例通常是轻质灯泡的灯丝,在此期间,由于电流膨胀,温度会升高。在这种情况下,不能应用欧姆定律。电灯泡灯丝违反欧姆定律。
欧姆定律的水管类比
欧姆定律描述了流过电阻的流量,一旦完全不同的电势(电压)平方测量应用于电阻的每个末端。由于我们往往看不到电子,水管类比有助于我们更高地感知电路。
在这里,电压类似于水压,它是流过管道的水量,因此电阻是管道的大小。一旦施加了很大的压力(电压),就会有大量的水流过管道(电流),因此管道越大(电阻越低)。
计算电力受害欧姆定律
该能量从移动电荷的功率再生为另一种类型的能量,如机械能、热、磁场或电场中保持的能量的速率,被认为是瓦特数。功率的单位是瓦特。电力是根据欧姆定律和电压、电流和电阻的值来计算的。
求幂公式:
When the values for voltage and current square measure are given,
P = VI
When the values for voltage and resistance square measure are given,
When the values for current and resistance square measure are given,
P = I2R
什么是幂三角?
一旦将相反的 2 参数单位的值提供给我们,功率三角形用于查看电功率、电压和电流的值。在功率三角形内,能力 (P) 位于最高处,电流 (I) 和电压 (V) 面积单位位于底部。
When the values of current and voltage are given, the formula for locating power is,
P = VI
When the values of power and voltage are given, the formula for locating current is,
When the values of power and current are given, the formula for locating voltage is,
欧姆定律矩阵表
就像上面显示的欧姆定律图表一样,我们能够将各个欧姆定律方程压缩成一个简单的矩阵表,如下所示,以便在精明的关联未知值时直接参考。Known values Resistance(R) Current(I) Voltage(V) Power (P) Current and Resistance R = I × R P = I2 × R Voltage and Current P = V × I Power and Current Voltage and Resistance Power and Resistance Voltage and Power
欧姆定律的主要应用是:
- 确认电路的电压、电阻或电流。
- 欧姆定律用于保持电子部件的指定跌落。
- 直流电表和不同的直流分流器还采用了欧姆定律来转移它。
欧姆定律的局限性:
以下是欧姆定律的约束:
- 欧姆定律不适用于二极管和晶体管等单边电子元件,因为它们只允许单边电子元件沿一个方向流动。
- 对于具有电容、电阻等参数的非线性电气元件,电压和电流不会随时间保持恒定。
电阻
当电流流过灯泡或任何导体时,导体会对此产生一些阻碍,这种阻碍被理解为电阻,用 R 表示。每种材料都与电阻有关,这通常是导体提供的解释一旦电流通过它就会产生热量。在接下来的几节中,让我们好好研究一下电阻。
什么是电阻?
根据欧姆定律,流经导体的电流与穿过导体的电现象之间存在关系。它是由,
V ∝ I V = IR
Where,
V is that the electric potential measured across the conductor (in volts)
I is that the current through the conductor (in amperes)
R is that the constant of quotient known as resistance (in ohms)
电路的电气现象是施加在其上的电压之间的大小关系。
Rearranging the relation,
The unit of an electrical phenomenon is ohms.
电荷仅流经某些材料而不是其他材料。电现象测量电路的间隔限制这种电现象的流量的比例。
影响电阻的因素
导体的电气现象取决于以下因素:
- 导体的横截面空间
- 导体长度
- 导体材料
- 导电材料的温度
电阻与导体的长度 (L) 成正比,与横截面空间 (A) 成反比。它由后续关系给出。
Where wherever is that the resistance of the fabric (measured in Ωm, ohm meter)
电阻率可以是材料抵抗流动电现象的能力的定性活动。显然,绝缘体可以比导体具有更好的电阻值。下面给出一些材料的电阻率以进行比较。偶尔具有电阻值的材料可以很好地导电。Material Resistivity Silver 1.00×10−8 Copper 1.68×10−8 Aluminum 2.82×10−8 Wood 1.00×1014 Air 2.30×1016 Teflon 1.00×1023
什么是电阻率?
概述电阻是因为在选定温度下每单位长度和单位横截面空间提供的欧姆电阻并用 ρ 表示。欧姆电阻也称为比欧姆电阻。电阻率的国际单位制单位是欧姆表。以下是电阻率的公式:
Where,
- ρ is that the electrical resistance of metal Ω.m
- E is that the electric field in V.m-1
- J is that the current density in A.m-2
示例问题
问题 1. 欧姆定律说明了什么?
回答:
Ohm’s law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
问题 2. 欧姆定律可以用来做什么?
回答:
Ohm’s law is employed to validate the static values of circuit parts like current levels, voltage provides, and voltage drops.
问题 3. 如果电熨斗的电阻为 60 Ω,电阻中流过 4.5 A 的电流。求两点之间的电压。
解决方案:
If we tend to ask to calculate the worth of voltage with the worth of current and resistance given to us, then cover V within the triangle. Now, we tend to left with I and R or additional exactly I × R.
Therefore, we tend to use the subsequent formula to calculate the worth of V:
V = I × R
Substituting the values in the equation, we get
V = 4.5 A × 60 Ω = 270 V
V = 270 V
问题 4. 12.0 V 的 EMF 电源连接到严格电阻的电器(灯泡)。 3.0 A 的电流流过它。考虑导线是无电阻的。计算电器提供的电阻。
解决方案:
When we are asked to search out the worth of resistance once the values of voltage and current are given, then we tend to cowl R within the triangle. This leaves us with solely V and that I, a lot of exactly .
Substituting the values in the equation, we get
R = 4 Ω
问题 5. 电阻率的倒数是多少?
回答:
The reciprocal of resistivity is conductivity.
问题6.纯金属的电阻随着温度的升高会发生什么变化?
回答:
As the temperature will increase, the resistance of pure metals increase. The rationale behind this is often the rise within the variety of electrons within the physical phenomenon band that reduces the quality thereby increasing the resistance.
问题 7. 绝缘子的电阻随着温度的升高会发生什么变化?
回答:
Because the temperature will increase, the resistance of insulators decreases. The rationale behind this is often the lepton movement from the physical phenomenon band to the valence band will increase because the energy gap between these two bands is massive. Therefore, the electrical phenomenon will increase and also the resistance decreases.
问题 8. 如果 0.7A 电流流过电阻。电阻两点的电压为14V。电阻的阻值是多少?
解决方案:
Here, Current, I = 0.7A
Potential difference or Voltage, V = 14V
Resistance, R =?
According to ohms law questions we know,
V = IR
Or, R =
=
= 20 Ω
问题 9. 电熨斗的电阻 60 Ω。 3.2A 电流流过电阻。求两点之间的电压。
解决方案:
Here, Resistance, R = 60 Ω.
Current, I = 3.2 A
Voltage, V = ?
From Ohm’s law,
V = IR
= 3.2 × 60
= 192V
问题 10. 确定代表一库仑电荷的电子数。
回答:
One electron acquires a charge of 1.6 ×10-19C, i.e., 1.6 ×10-19C of charge is enclosed in 1 electron.
∴ 1 C of charge is enclosed in 1/1.6 × 10-19 = 6.25 × 1018 = 6 × 1018
Therefore, 6 × 1018 electrons compose one coulomb of charge.
问题 11. 让元件两端的电位降降低到原来值的一半,而电子元件的电阻保持不变。通过它的电流可以发生什么修改?
解决方案:
According to Ohm’s law
V = IR
… (1)
Now Potential difference is decreased to half
∴ New potential difference
Resistance remains constant
So the new current
问题 12. 随着温度的升高,绝缘体的电阻会发生什么变化?
回答:
Because the temperature will increase, the resistance of insulators decreases. The rationale behind this is often the lepton movement from the physical phenomenon band to the valence band will increase because the energy gap between these two bands is massive. Therefore, the electrical phenomenon will increase and also the resistance decreases.