（1）电源电压是多少？这时R2中的电流是多少？（2）当S1，S2都断开时，一分钟R1产生的热量是多少？
\u7535\u963bR1\uff1aR2=2\uff1a1\uff0c\u82e5\u5c06R1\u4e0eR2\u4e32\u8054\u540e\u63a5\u5728\u7535\u538b\u4e3aU\u7684\u7535\u6e90\u4e0a\uff0c\u5728\u65f6\u95f4T\u5185\u7535\u6d41\u901a\u8fc7R1\u4ea7\u751f\u7684\u70ed\u91cf\u4e3aQ1\uff0c\u82e5\u5c06R1\u4e0eR2Q1=i^2RT=((2/3U)/R1)^2*R*T=4/9*U^2/R1*T
Q2=i^2RT=(U/R1)^2*R1*T=U^2/R1*T
Q1:Q2=4:9
1\u3001s1,s2\u90fd\u95ed\u5408\uff0cR2\u548cR3\u5e76\u8054\uff0c\u5728R3\u4e2d\uff0c\u7535\u6e90\u7535\u538b\uff1aE=I1*R3=0.6*30=18v
2\u3001s1,s2\u90fd\u65ad\u5f00\uff0cR1\u548cR3\u4e32\u8054\u3002\u603b\u7535\u963b\uff1aR13=10+30=40\u6b27
3\u3001R1\u548cR3\u4e32\u8054\u7535\u6d41\uff1aI13=E/R13=18/40=0.45A
4\u3001R1\u529f\u7387\uff1aP1=I13*I13*R1=0.45*0.45*10=2.025W
5\u30011\u5206\u949fr1\u6d88\u8017\u7684\u7535\u80fd\uff1aW=PT =2.025*60=121.5\u7126
电源电压U=IR3=0.6A×30Ω=18V R2两端的电流I2=U/R2=18/20A=0.9A
（2）当开关全断开时，R1与R3串连接入电路，则电路中的电流：
I=U/(R1+R3)=18/(6+30)=0.5A
t=1min=60s；
则1分钟内R1上产生的热量Q=I2R1t=（0.5A）^2×10Ω×60s=150J
18V 45J。。。自己算的，应该没错
图看不清
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