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本文介绍一种取材容易,操作简单,可见度大,重复实验方便的热膨胀演示方法.装置如图所示,木板长2.1m,宽10cm,两端旋紧二螺丝A、B,螺丝连出导线.取800W的电炉丝一条,将圆珠笔芯插入卷绕的电炉丝中,边拉边旋转,很容易将卷绕的电炉丝拉直作电阻丝用,电阻丝紧固在螺丝上,以拨动时能发出清晰的琴弦声为佳,在电阻丝中间O点挂上小钢球,电阻丝几乎还是拉直的,将低压电源(或可调变压器)及电压表连成图示的电路,预先在电阻丝各处粘上石蜡(蜡烛油、松香、焊锡膏也可),通电后电阻丝发热使石蜡挥发成烟雾,同时小球下降到O′点,电阻丝受热膨胀被拉
This article describes a thermal expansion demonstration method with easy material acquisition, simple operation, large visibility, and easy repetitive experiments. The device is shown in the figure. The length of the board is 2.1m and the width is 10cm. Both ends are screwed with two screws A and B, and the screws are connected to the wires. Take an electric wire of 800W, insert the ball-point refill into the coiled electric wire, and pull and rotate it, it is easy to straighten the wound electric wire for resistance wire, and the resistance wire is fastened to the screw to It is better to emit a clear string sound. A small steel ball is hung in the middle of the resistance wire, the resistance wire is almost straightened, and the low voltage power supply (or the adjustable transformer) and the voltmeter are connected to the circuit shown in the figure. The paraffin wax (candle oil, rosin, and solder paste) can be applied to all parts of the resistance wire. After the power is applied, the resistance wire heats up and the paraffin wax volatilizes into smoke. At the same time, the ball is dropped to the O’ point, and the resistance wire is pulled by the thermal expansion.