在图1所示的电路中,电源电压保持6伏不变, R 1 的阻值为10欧。闭合电键S,电压表的示数如图2所示。
在图1所示的电路中,电源电压保持6伏不变,R1的阻值为10欧。闭合电键S,电压表的示数如图2所示。⑴求通过电阻R1的电流。⑵求电阻R2的阻值。⑶现有阻值分别为2欧、10欧...
在图1所示的电路中,电源电压保持6伏不变, R 1 的阻值为10欧。闭合电键S,电压表的示数如图2所示。 ⑴ 求通过电阻 R 1 的电流。⑵ 求电阻 R 2 的阻值。⑶ 现有阻值分别为2欧、10欧、50欧、100欧的四个定值电阻,请选择其中一个定值电阻替换电路中的电阻 R 2 ,要求:电压表选择合适的量程后,闭合闭合开关S,能使电压表指针偏离到图所示电压的一半。请判断:所提供的四个定值电阻是否符合要求,若有符合,请具体说明是___________电阻,并指出电压表所选用的量程;若不符合,请说明理由。
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2014-09-15
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(1)0.2A(2)20Ω(3)2Ω和50Ω符合要求 |
试题分析:⑴∵电源电压为6伏, R 1 与 R 2 串联,且电压表并联在 R 1 两端 ∴电压表示数为2伏,即 R 1 两端电压 U 1 为2伏 1分 ∴ I 1 = ![](https://iknow-pic.cdn.bcebos.com/cc11728b4710b9122c4c224fc0fdfc03934522f6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/9922720e0cf3d7ca2671ebc7f11fbe096a63a9f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =0.2安 2分 ⑵∴ I 2 = I 1 =0.2安 ∴ U 2 = U 总 - U 1 =6伏-2伏=4伏 1分 ∴ R 2 = ![](https://iknow-pic.cdn.bcebos.com/4610b912c8fcc3ce254d1d829145d688d53f20f6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/0df3d7ca7bcb0a46ada55f886863f6246a60aff8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =20欧 2分 ⑶若电压表量程不换时,电压表指针偏离零刻度线的角度是原来的一半,则 U 1 ′ 为1伏 ∴ I 1 ′ = ![](https://iknow-pic.cdn.bcebos.com/f31fbe096b63f62408daedb28444ebf81b4ca3f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/0b46f21fbe096b63949e8ae10f338744eaf8acf8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =0.1安 ∴ I 2 ′ = I 1 ′ =0.1安 ∴ U 2 ′ = U 总 - U 1 ′=6伏-1伏=5伏 ∴ R 2 ′ = ![](https://iknow-pic.cdn.bcebos.com/8644ebf81a4c510fb04336ab6359252dd52aa5f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/8694a4c27d1ed21be144fa54ae6eddc450da3ff6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =50欧 1分 若电压表量程更换时,电压表指针偏离零刻度线的角度是原来的一半,则 U 1 ′ 为5伏 ∴ I 1 ′ = ![](https://iknow-pic.cdn.bcebos.com/f31fbe096b63f62408daedb28444ebf81b4ca3f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/0d338744ebf81a4c39b53878d42a6059242da6f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =0.5安 ∴ I 2 ′ = I 1 ′ =0.5安 ∴ U 2 ′ = U 总 - U 1 ′=6伏-5伏=1伏 ∴ R 2 ′ = ![](https://iknow-pic.cdn.bcebos.com/8644ebf81a4c510fb04336ab6359252dd52aa5f8?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/b7fd5266d016092451a876aad70735fae7cd34f6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =2欧 1分 因此,在所提供的四个定值电阻中有两个电阻符合要求, 它们是2欧和50欧。 点评:关键是欧姆定律和串联电路特征的灵活运用,第3问中看似较难,实则能分析清楚题意,分解为若干个小题进行解题,其实物理题大多都这样,所以注意练习,注重方法的掌握。 |
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