Farhang Amiri

The Phase Shift in the Jumping Ring.

The popular physics demonstration experiment known as Thomsons Jumping Ring (JR) has been variously explained as a simple example of Lenzs law, or as the result of a phase shift of the ring current relative to the induced emf. The failure of the first-quadrant Lenzs law explanation is shown by the time the ring takes to jump and by levitation. A method is given for measuring the phase shift with results for aluminum and brass rings.

A general principle for light reflecting from a uniformly moving mirror: A relativistic treatment

We investigate the reflection of light from a mirror moving at relativistic speeds and introduce a general principle to determine the relationship between the incident and reflected angles. This principle states that the momentum change of each photon is perpendicular to the surface of the mirror. We carry out sample calculations for various geometries.

Simple Experiments to Study the Earth's Magnetic Field

A set of simple experiments is outlined for determining the magnetic field of the Earth. These experiments can be performed by students from high school to college and will help them gain a greater appreciation of the three-dimensional nature for the Earths magnetic field. Reasonably accurate measurements of the field strength, its components, and dip angle are possible through use of a transparent solenoid, a compass, and a Magnaprobe.

The Square Light Clock and Special Relativity

A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45° angle at each corner of a square of length L0, shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By studying the same cycle of events measured in a frame of reference where the square light clock is in motion with speed of v, we can derive both time dilation and, independently, length contraction. This will be done by analyzing the changing dimensions and also the one-cycle timing for this square light clock.

Thomson’s Jumping Ring Over a Long Coil

The classic jumping ring apparatus consists of a coil with an iron core that extends out of the coil. A copper or aluminum ring placed over the iron core jumps upward when AC power is applied to the coil. In this paper we will examine a modified design of the jumping ring apparatus, called the “long-coil design.” It allows the ring to jump upward or downward, depending on the starting position of the ring. These features shed significant light on the study of the force that causes the ring to jump.

DC-Powered Jumping Ring

The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

Correlated nuclear and thermal measurements in D/Pd and H/Pd systems

Gas loaded D/Pd and H/Pd rods (1 mm diameter) were used to investigate correlated thermal and nuclear effects. Simultaneous measurements were made of gas pressure, electric current, voltage drops, rod and chamber temperature, and neutrons. D/Pd and H/Pd ratios were monitored by resistance changes in the rod segments. Two deuterium runs (totaling 3000+ hours), one hydrogen run (nearly 1000 hours), and background runs (nearly 2000 hours) have been completed. two neutron bursts were recorded in the first deuterium experiment. No bursts, but periods of increased activity, were observed in the second deuterium run. No increased activity was observed in the hydrogen experiment. Accurate agreement with Poisson counting statistics was found in the background and hydrogen runs. Neutron bursts observed in the first deuterium run exceeded, by several orders of magnitude, the Poisson prediction. A slight resistance increase in one rod segment was observed during one of the neutron bursts. No simultaneous increase in ...

Heavy meson pair production in polarized e+e− annihilation

Abstract We study the exclusive production of heavy mesons in polarized e+e− annihilations using a perturbative QCD calculation. We discuss the significance of polarized beams in isolating electroweak effects at high energies, and calculate the left-right asymmetry and forward-backward asymmetry for different collider energies.