Question

如圖所示的電路中，電源電壓為8V，R₂是阻值為40的定值電阻，壓敏電阻R₁的阻值隨壓力的變化情況如圖乙所示。當(dāng)開關(guān)S閉合后，問(wèn)：

（1）當(dāng)壓敏電阻R₁受到的壓力從0增加到3N的過(guò)程中，電流表示數(shù)的變化是       （填“增大”“減少”）？

（2）當(dāng)電流表示數(shù)為0.4A時(shí)，壓敏電阻受到的壓力為多少？

（3）當(dāng)電路連續(xù)工作10mim，電阻R₂產(chǎn)生的熱量為多少？

（4）若此熱量的84%給20g的水加熱，則水溫升高多少？（水的比熱容為）

Answer 1

（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)