电路如图，R1=R2=R3=R4=R=10欧姆，第一问当开关S闭合时，电路等效电阻 在图所示的电路中，已知R1=R2=R3=R4=3欧，当电键K...
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\u7b49\u6548\u7535\u8def\u56fe\u5982\u56fe\u6240\u793a\uff1a\u7531\u7535\u8def\u56fe\u53ef\u77e5\uff0cR2\u3001R3\u3001R4\u5e76\u8054\u540e\u4e0eR1\u4e32\u8054\uff0c\u7535\u538b\u8868\u6d4b\u7535\u6e90\u7684\u7535\u538b\uff0c\u5373\u7535\u6e90\u7684\u7535\u538bU=12V\uff1b\u5e76\u8054\u90e8\u5206\u7684\u603b\u7535\u963bR\u5e76=13R2=13\u00d73\u03a9=1\u03a9\uff0c\u7535\u8def\u4e2d\u7684\u603b\u7535\u6d41I=UR1+R\u5e76=12V3\u03a9+1\u03a9=3A\uff0c\u5e76\u8054\u90e8\u5206\u7684\u7535\u538bU\u5e76=IR\u5e76=3A\u00d71\u03a9=3V\uff0c\u7535\u6d41\u8868\u7684\u793a\u6570I\u2032=U\u5e76R2+U\u5e76R3=3V3\u03a9+3V3\u03a9=2A\uff0e\u6545\u9009B\uff0e
（1）当开关s断开时电阻R1和R2并联，电阻R3和R4串联后再与R2并联，
所以R34＝R3+R4＝20（欧姆）
R12＝R1/2＝10/2＝5（欧姆）
则等效电阻R＝R12*R34/（R12+R34）＝20*5/（20+5）＝4（欧姆）
（2）当开关s闭合时
电阻R1、R2和R4并联，而R3被短接
所以等效电阻R＝R1/3＝10/3＝3.3（欧姆）
绛旓細R2銆丷3銆丷4骞惰仈鍚庣殑鐢甸樆R123=3惟3=1惟锛孯鎬=R1+R123+R=3惟+1惟+1惟=5惟锛孖=UR鎬=12V5惟=2.4A锛孯2銆丷3銆丷4骞惰仈鍐嶅拰R1涓茶仈鍚庣殑鐢靛帇锛歎鈥=I锛圧1+R123锛=2.4A脳锛3惟+1惟锛=9.6V锛孯2銆丷3銆丷4骞惰仈锛R2=R3=R4锛孯2銆丷3骞惰仈鍚庣殑鐢垫祦I鈥=23I=23脳2.4A=1.6A锛庢晠绛旀涓猴細5惟...
绛旓細澶鐢佃矾鎬荤數闃讳负R鎬=R+R1+13R2=1+3+13脳3=5惟鏍规嵁娆у瀹氬緥寰楋紝鎬荤數娴佷负I=UR鎬=125A=2.4A鐢甸樆R1鐨勭數鍘嬩负U1=IR1=3脳2.4V=7.2V骞惰仈閮ㄥ垎鐢靛帇涓篣骞=I2?13R2=2.4脳1V=2.4V鎵浠ョ數鍘嬭〃鐨勭ず鏁颁负UV=U1+U骞=9.6V鐢垫祦琛ㄧ殑绀烘暟涓篒A=2I2=2U骞禦2=2脳2.43A=1.6AR2娑堣楃殑鐢靛姛鐜囦负P=I...
绛旓細锛1锛夊綋寮鍏硈鏂紑鏃 鐢甸樆R1鍜R2骞惰仈锛岀數闃籖3鍜孯4涓茶仈鍚庡啀涓嶳2骞惰仈锛屾墍浠34锛漅3+R4锛20锛堟濮嗭級R12锛漅1/2锛10/2锛5锛堟濮嗭級鍒欑瓑鏁堢數闃籖锛漅12*R34/锛圧12+R34锛夛紳20*5/锛20+5锛夛紳4锛堟濮嗭級锛2锛夊綋寮鍏硈闂悎鏃 鐢甸樆R1銆丷2鍜孯4骞惰仈锛岃孯3琚煭鎺 鎵浠ョ瓑鏁堢數闃籖锛漅1/3锛10/3锛3.3锛堟濮嗭級
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绛旓細绛夋晥鐢佃矾鍙互鐪嬪嚭浠栦滑鐨勫叧绯讳负锛R1//[R2+(R3//R4)]R3//R4=2娆у R2+2=6娆у R1//6=3娆у銆傛墍浠ユ渶鍚庣瓑浜3娆у 锛2锛夛細鐣欒繃R1鐨勭數娴佷负2A 鍙緱Uab=2*4=8V 鐣欒繃R2鐨勭數娴佷负8/6=1.33333A 淇濈暀涓や綅灏忔暟寰1.33A
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