推荐回答(3个)
500Ω。
以荣帝灯饰先来说一个灯珠的情况,电源电压为12V,如下图所示小灯珠的压降为2V,额定电流是20ma,求我们需要串联一个多大的电阻?这时候电阻的分压V=12-2=10V,而流过电阻的电流为20ma,所以电阻的阻值R=10V➗20ma=0.5KΩ,即500Ω。
串联了两个灯珠,参数和上面的一致,压降为2V、电流为20ma,求此时电阻的阻值?和上面一样我们先算出电阻此时的压降。U=12-2-2=8V,同样流过的电流为20ma,所以此时的电阻:R=8V➗20ma=0.4KΩ,即400Ω。
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扩展资料
并联
下面荣帝灯饰说一下并联的情况,两个灯珠并联,求电阻的阻值,首先我们要知道,并联电压不变,电流相加,两个灯珠的压降为2V,而通过它们的总电流为40ma,此时加在电阻身上的电压同样为10V,12-2=10V,而此时的电阻R=10V➗40ma=0.25K,即250Ω。
这类问题的一般步骤是先算出电阻身上的压降,然后算出流过灯珠的电流,这样既可求出我们需要的电阻。上述的2、3例中两个灯珠的发光效果完全一样,但是因为电路结构的变化,电阻将近减少了一半。
应该根据灯珠颜色来区分发光电流的大小,分别串接不同阻值的电阻对待:
2V左右点亮的LED灯(如红、黄、橙黄等)供电电压(V)电阻阻值(欧姆)
3V 51欧
4.5V 120欧
5V 150欧
6V 180欧
7V 220欧
9V 330欧
12V 470欧
12(车上12V) 680欧
3V左右点亮的LED灯(如蓝、绿、白等等)电阻阻值(OHM欧姆)
3V 1欧
4.5V 69欧
5V 100欧
6V 150欧
7V 180欧
9V 270欧
12V 390欧
12(车上12V) 470欧
用12V电接一个LED应该串连一个多大的电阻?
取2K~4K就行。
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