试题与答案

(10分)如图所示为某研究性学习小组自制的电子秤原理图,电源电动势为E,内阻不计

题型:计算题

题目:

(10分)如图所示为某研究性学习小组自制的电子秤原理图,电源电动势为E,内阻不计,C是限流电阻,AB为一均匀的滑动变阻器,长度为L,P是滑动头,与弹簧上端连接,可保持水平状态随弹簧的长度变化而上下自由滑动。限流电阻和滑动变阻器的电阻相等。弹簧处于原长时,P刚好指着A端.已知弹簧的劲度系数为k,当地的重力加速度为g,电压表可视为理想电表,不计一切摩擦和其它阻力。当在弹簧上放上托盘时,电压表的示数为U0;当托盘上放有物体时,电压表的示数为U,求:(1)物体的质量;(2)如果长期使用,电源的电动势会变小,这样(指计算仍取原数值)测得的物体质量会怎样?

答案:

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参考答案:B

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