将光敏电阻R和定值电阻R0、电流表、电压表连接成电路，接在9V的电源上，如图．光敏电阻阻值随光强变化关
\u5c06\u5149\u654f\u7535\u963bR\u548c\u5b9a\u503c\u7535\u963bR 0 \u3001\u7535\u6d41\u8868\u3001\u7535\u538b\u8868\u8fde\u63a5\u6210\u7535\u8def\uff0c\u63a5\u57289V\u7684\u7535\u6e90\u4e0a\uff0c\u5982\u56fe\u6240\u793a\u3002\u5149\u654f\u7535\u963b\u963b\u503c\u968f\u5149\u5f3a\uff081\uff09\u589e\u5927 \uff082\uff0964.8J \uff083\uff090.25A \u8bd5\u9898\u5206\u6790\uff1a\uff081\uff09\u82e5\u7535\u6d41\u8868\u7684\u793a\u6570\u589e\u5927\uff0c\u6839\u636e\u516c\u5f0fI="U" R \u53ef\u77e5\u7535\u8def\u7535\u963b\u53d8\u5c0f\uff0c\u5149\u654f\u7535\u963b\u7684\u963b\u503c\u53d8\u5c0f\uff0c\u7531\u8868\u4e2d\u6570\u636e\u53ef\u77e5\u5149\u5f3a\u589e\u5927\uff0e\uff082\uff09\u7531\u8868\u4e2d\u6570\u636e\u53ef\u77e5\u5f53\u5149\u5f3aE=2cd\u65f6\uff0c\u5149\u654f\u7535\u963b\u963b\u503cR=18\u03a9\uff0c\u6b64\u65f6\u7535\u8def\u4e2d\u7684\u603b\u7535\u963b\u4e3a \u5b9a\u503c\u7535\u963b\u963b\u503c\u4e3a \u901a\u75351min\uff0cR 0 \u4e0a\u4ea7\u751f\u7684\u70ed\u91cf\uff1a \uff083\uff09\u7531\u8868\u4e2d\u6570\u636e\u53ef\u77e5\uff1a\u5149\u5f3a\u4e0e\u5149\u654f\u7535\u963b\u7684\u4e58\u79ef\u4fdd\u6301\u4e0d\u53d8\uff0c\u5149\u654f\u7535\u963b\u963b\u503c\u4e0e\u5149\u5f3a\u6210\u53cd\u6bd4\uff0c\u7531\u8868\u4e2d\u6570\u636e\u77e5\uff1a1cd\u00d736\u03a9=1.5cd\u00d7R\uff0c\u5219R=24\u03a9\uff0c\u6b64\u65f6\u7535\u6d41\u8868\u793a\u6570\u4e3a \uff0e
\uff081\uff09\u82e5\u7535\u6d41\u8868\u7684\u793a\u6570\u589e\u5927\uff0c\u6839\u636e\u516c\u5f0fI=UR\u53ef\u77e5\u7535\u8def\u7535\u963b\u53d8\u5c0f\uff0c\u5149\u654f\u7535\u963b\u7684\u963b\u503c\u53d8\u5c0f\uff0c\u4ece\u8868\u4e2d\u53ef\u77e5\u5149\u5f3a\u589e\u5927\uff0c\u6b64\u65f6\u5b9a\u503c\u7535\u963b\u4e24\u7aef\u7684\u7535\u538b\u53d8\u5927\uff0c\u6839\u636e\u4e32\u8054\u7535\u538b\u7684\u89c4\u5f8b\u53ef\u77e5\uff0c\u5149\u654f\u7535\u963b\u4e24\u7aef\u7684\u7535\u538b\u51cf\u5c0f\uff0c\u4e5f\u5c31\u662f\u7535\u538b\u8868\u793a\u6570\u51cf\u5c0f\uff0e\uff082\uff09\u7531\u8868\u4e2d\u6570\u636e\u53ef\u77e5\uff0c\u5149\u5f3a\u4e0e\u5149\u654f\u7535\u963b\u7684\u4e58\u79ef\u4fdd\u6301\u4e0d\u53d8\uff0c\u6240\u4ee5\u5149\u654f\u7535\u963b\u968f\u5149\u5f3a\u7684\u53d8\u5316\u662f\u4e00\u4e2a\u53cd\u6bd4\u4f8b\u51fd\u6570\uff1b\u22351cd\u00d718\u03a9=1.5cd\u00d7R\uff0c\u2234R=12\u03a9\uff1b\u5149\u654f\u7535\u963b\u4e24\u7aef\u7684\u7535\u538b\uff1aU1=IR=0.5A\u00d712\u03a9=6V\uff0c\u5b9a\u503c\u7535\u963b\u4e24\u7aef\u7684\u7535\u538b\uff1aU0=U-U1=9V-6V=3V\uff0cR0=U0I0=3V0.5A=6\u03a9\uff0cQ0=\uff08I\uff092Rt=\uff080.5A\uff092\u00d76\u03a9\u00d760s=90J\uff0e\u6545\u7b54\u6848\u4e3a\uff1a\uff081\uff09\u589e\u5927\uff0c\u51cf\u5c0f\uff1b\uff082\uff09\u53cd\u6bd4\u4f8b\uff0c12\uff0c90\uff0e
（1）当电流表示数增大时，∵I=
| U |
| R |
∴由R=
| U |
| I |
由表格中数据可知光强在增大；
（2）由表格数据可知，当光强E=2cd时，光敏电阻的阻值R=18Ω，
此时电路中的总电阻：
R总=
| U |
| I |
| 9V |
| 0.3A |
∵串联电路中总电阻等于各分电阻之和，
∴R0=R总-R=30Ω-18Ω=12Ω；
（3）由表中数据可知，光强与光敏电阻的乘积保持不变，所以光敏电阻随光强的变化是一个反比例函数；
∵1cd×36Ω=1.5cd×R′，
∴R′=24Ω，
此时电流表的示数：
I′=
| U |
| R0+R′ |
| 9V |
| 12Ω+24Ω |
答：（1）增大；
（2）定值电阻R0为12Ω；
（3）当光强E=1.5cd时，电流表示数是0.25A．
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