如图所示的电路中,电源电压为8V,R2是阻值为40的定值电阻,压敏电阻R1的阻值随压力的变化情况如图乙所示。当...
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问题详情:
如图所示的电路中,电源电压为8V,R2是阻值为40的定值电阻,压敏电阻R1的阻值随压力的变化情况如图乙所示。当开关S闭合后,问:
(1)当压敏电阻R1受到的压力从0增加到3N的过程中,电流表示数的变化是 (填“增大”“减少”)?
(2)当电流表示数为0.4A时,压敏电阻受到的压力为多少?
(3)当电路连续工作10mim,电阻R2产生的热量为多少?
(4)若此热量的84%给20g的水加热,则水温升高多少?(水的比热容为)
【回答】
(1)增大。········································································································ (2分)
(2)I2=U/R2=8V/40Ω=0.2A
I1=I-I2=0.4A-0.2A=0.2A···································································· (1分)
R1= U/ I1=8V/0.2A=40Ω
F=2N··································································································· (1分)
(3)Q2= I22 R2t=(0.2A)2×40Ω×10×60s=960J·················································· (2分)
(4)Q吸=cm△t·························································································· (1分)
△t =
=9.6℃······························································································ (1分)
知识点:电功率单元测试
题型:计算题
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