Authors : Janchai YINGPRAYOON and Warangkana PORNKO

Page Nos : 41-45

Description :
Some experimental data need to be carried out in a short span of time. It is not possible to measure the time manually using a normal stopwatch. Some can be done by using a highspeed photography. An alternative way of a measurement of short time accurately with the help of an electronic RC-charging circuit is designed and presented in this work. The time measurement starts by charging a capacitor C through a resistor R. The voltage across a capacitor, Vc is an exponential function of time t with the constant values of R, C and a constant voltage supply Vs of the circuit. The voltage across a capacitor C can be measured by using a datalogger with high sampling rate. The voltage charging across capacitor Vc is very fast and the charging time t can be calculated from the equation 𝑉! = 𝑉"(1 − 𝑒# ! "#). This time measurement can be applied to a free-falling object experiment in order to calculate the acceleration due to gravity, g.

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