欧姆定律和计算电功率的 P= IV 是否有矛盾?

式一: I = V/R if I Be the subject
it me the I be the constants
whan a fixed Current is given
if you supplied a double voltage
the resistance will double as well to gain a congreunt current
so WHEN I IS FIXED
THE VOLTAGE AND RESISTANCE IS PROPORTIONAL. 式二: I = P/V Similarly to above
if I Be the subject
it me the I be the constants
whan a fixed Current is given
if you supplied a double voltage
you gain a double power when keeping a fixed current
so WHEN I IS FIXED
THE VOLTAGE AND POWER IS PROPORTIONAL. From the formulae
you get it P=IV V=IR P=I(V) P=I(IR) P=I^2R
好简单其实 一式.V=IR 二式.P=VI 一式. V系指某两点之间既POTENTIAL DROP. I 系指流经果两点之间既CURRENT. R 系指两点之间既RESISTANCE.将V变大一倍
由于R 不变
所以 I 会大一倍 二式.P系指某两点之间既POWER COMSUMPTION. V 系指两点之间既 POTENTIAL DROP. I 系指两点之间既 CURRENT. 如果你要将V加大一倍. 由一式可见其实系要将I都会系加大一倍. 所以其实二式入面P
V
I
冇一个系CONSTANT. 若要将V加大一倍
I自然会加大一倍
最后POWER CONSUMPTION 就会变为原本的4倍 最后. P=V^2/R 根据头先所讲
你将V加大一倍
POWER应该系变原本4倍
呢条式入面RESISTANCE OF LOAD 系唔会变
P=4(V' ^2)/ R 所以呢条式系岩既 至于呢条式点黎
咪就系结合式一同式二
我谂你都系因为觉得式一式二错先问呢个问题
式一同式二系两回事 式一: I = V/R 计电阻
电流与电压 和 式二: I = P/V 计功率
电流与电压 式一非常简单
电压除电阻等于电流
但系冇计功率
代替计算就系 V = IR I = V/R R = V/I 但系式二就复杂啲
电压乘电流等于功率系冇错
但系如果计电压电阻与功率就麻烦啲
方法有2 1. 先计 P = VI
然后 R = V/I 2. 直接计 P = V^2/R 或者 P = I^2R 擧个例子 V = 3.6V I = 2.4A R = 1.5Ω P = 8.64W V = IR = 2.4A * 1.5Ω = 3.6V I = V/R = 3.6V / 1.5Ω = 2.4A R = V/I = 3.6V / 2.4A = 1.5Ω P = VI = 3.6V * 2.4A = 8.64W P = V^2/R = 3.6V * 3.6V / 1.5Ω = 12.96 /1.5Ω = 8.64W P = I^2R = 2.4A * 2.4A * 1.5Ω = 5.76 * 1.5Ω = 8.64W 希望帮到你
Your equation (1) I = V/R is a basic law
the Ohm's Law. It is true under the condition that the resistance R is constant. Hence
any increase of voltage V leads to a corresponding increase of current I. In equation (2)
current I and voltage V are inversely proportional if
and only if
the value of power P is a constant. Under normal circumstances
this is not the case. From Ohm's Law
power P can be expressed as V^2/R. Hence
your equation (2) is actually
I = [V^2/R]/V When V increases
the power P not only increases
but would increase to a much larger extend because P depends on V^2. As a rsult
this leads to the increase in current I as calculated from equation (1). You could easily see that equation (2) and equation (1) are actually identical. I = = [V^2/R]/V just reduces to I = V/R
唔知你认为有咩矛盾呢﹖式一中I同V系正比，而式二I同V系反比，只要你两条式系正确嘅话，睇唔到有问题。或者你去观察一啲电器可以用110V同220V，你睇睇灰士(FUSE/保险丝)系110V或220V时应该用几多A，可以话你知系唔同AMP数，你想知点解，用你嘅公式计计。
问题在于式二，若V加大一倍
P都会加大一倍，而不是I 变小了一倍。 此外欧姆定律和计算电功率的 P= IV 是没有矛盾，因P=IV
(I square)R=IV
V=IR。它们都是相通的。
参考: my knowledge

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