An improvement of the experiment with a driven pendulum is proposed: during a run, the phase shift between the driving force and displacement is continuously displayed vs. frequency. The method of phase measurements is taken from the lock-in detection technique. Using the new PASCO data acquisition system, the measurements in a frequency range…

Nowadays, the use of data-acquisition systems in undergraduate laboratories is routine. Many computer-assisted experiments became possible with the PASCO scientific data-acquisition system based on the 750 Interface and DataStudio software. A new data-acquisition system developed by PASCO includes the 850 Universal Interface and Capstone software.…

Using a data-acquisition system, the charge and energy stored in a capacitor are measured and displayed during the charging/discharging process. The experiment is usable as a laboratory work and/or a lecture demonstration. (Contains 3 figures.)

Two computer-assisted experiments are described: (i) determination of the speed of ultrasound waves in water and (ii) measurement of the thermal expansion of an aluminum-based alloy. A new data-acquisition system developed by PASCO scientific is used. In both experiments, the "Keep" mode of recording data is employed: the data are…

Electron-atom collisions in gases are an aspect of atomic physics. Three experiments in this field employing a thyratron are described: (i) the Ramsauer-Townsend effect, (ii) the excitation and ionization potentials of xenon and (iii) the ion-electron recombination after interrupting the electric discharge.

The experiments presented show the response of a liquid crystal shutter to applied electric voltages and the delay of the operations. Both properties are important for liquid crystal displays of computers and television sets. Two characteristics of the shutter are determined: (i) the optical transmittance versus applied voltage of various…

The "LCR" circuit is an important topic in the course of electricity and magnetism. Papers in this field consider mainly the forced oscillations and resonance. Our aim is to show how to demonstrate the free and self-excited oscillations in an "LCR" circuit. (Contains 4 figures.)

Digital storage oscilloscopes (DSOs) are now easily available to undergraduate laboratories. In many cases, a DSO can replace a data-acquisition system. Seven such experiments/demonstrations are considered: (i) families of "I-V" characteristics of electronic devices (bipolar junction transistor), (ii) the "V-I" curve of a high-temperature…

Computer-assisted experiments with CdS and CdSe photoresistors are described. The most important characteristics of the photoresistors are determined: (i) the spectral response, (ii) the photocurrent versus incident radiant power, (iii) the rise and decay time constants and (iv) the frequency response to modulated light. The photoconductivity gain…

The capacitance versus voltage relationship (the "C-V" characteristic) of a varicap is determined, and the device is used for tuning an "LC" circuit and for building a voltage-controlled oscillator. With a data-acquisition system, the "C-V" characteristic can be demonstrated in a short time. The necessary equipment includes a function generator,…

A laser diode from an inexpensive laser pen (laser pointer) is used in simple experiments. The radiant output power and efficiency of the laser are measured, and polarization of the light beam is shown. The "h/e" ratio is available from the threshold of spontaneous emission. The lasing threshold is found using several methods. With a…

Three variants of the rotational viscometer employing a dc motor are considered. The viscometers are highly suitable for liquids of high viscosity, such as glycerol or oils (that is, for [eta] in the range 10-1000 mPa s). The set-ups are very simple and can serve as a first step to designing devices that are more complicated. Experimentation with…

Two experiments related to standing sound waves in air are adapted for using the ScienceWorkshop data-acquisition system with the DataStudio software from PASCO scientific. First, the standing waves are created by reflection from a plane reflector. The distribution of the sound pressure along the standing wave is measured. Second, the resonance…

Employment of a data-acquisition system for data collection and calculations makes experiments with antennas more convenient and less time consuming. The determined directional patterns of the dipole antennas of different lengths are in reasonable agreement with theory. The enhancement of the signal by using a reflector is demonstrated, and a…

A common moving-coil (dynamic) loudspeaker is a device very suitable for teaching the general features of oscillating systems. As an addition to a previous paper (Kraftmakher 2009), this paper includes the following topics: (i) a new design of the optical sensor for measuring the cone oscillations; (ii) positive feedback and self-excited…