What it shows:

The basic principles of the parallel plate capacitor made large.

How it works:

The capacitance C of a simple parallel plate capacitor is given by


the ratio of the magnitude of the charge Q on either conductor...

A replica of Franklin's Thunder House demonstating the efficacy of his invention—the lightning rod. The class will get a charge out of this one.

A neutral conductor (or dielectric) experiences a torque, but no net force, when placed in a uniform electric field. It does experience a net force in a non-uniform field.

What it shows:

When an electrically neutral object is suspended in a uniform electric field, it becomes polarized. The electric force on the separated charges produces a torque about the suspension point and the object rotates. There is no translational motion—the object simply aligns itself with the electric field.

When an electrically neutral object is...

What is shows:

A neutral system of charges is rearranged...charge measured on one part is equal and opposite to the charge on another part. In that respect, this demonstration is not much different from the " 3 Sig Figs" demo in which voltage measurements are used. Conservation of charge is typically introduced in the first few lectures of an E&M course, before the concepts of voltage and capacitance are discussed. If voltage is the quantity...

What it shows:

Electricity is never created or destroyed, but only transferred. Rubbing fur and Teflon™ together transfers charge (electrons) from the fur to the Teflon, making the Teflon negatively charged. Conservation of charge requires the fur to become equally and oppositely charged as is demonstrated in this experiment to an accuracy of ≤1%.

How it works:

The difficulty in demonstrating charge conservation quantitatively lies in catching all the charge before it leaks away, the fur being the main problem. This is overcome...

What it shows:

As long ago as 600 B.C., the Greek philosopher Thales knew that amber, when rubbed, would attract bits of paper and other light objects. Many other substances have this same property and can be electrified by rubbing. The kind of electrification (positive or negative) depends on the substances used.

...

Two tuning forks with similar frequencies; one fork is variable in frequency to tune beating.

What it shows:

The interference of waves from two tuning forks of slightly differing frequencies gives rise to beating, that is, a modulated wave of frequency.

ν_b = (ν₁ - ν₂)

How it works:

Using two tuning forks of 256Hz, with one of the pair having small clamps (see figure 1) attached to the fork's limbs. These alter the fork's resonant frequency, and adjustment of the clamp...

What it shows: 

Bell plates are polygonal-shaped flat pieces of sheet metal which, when held in the hand and struck with a beater, produce a pleasant, sustained, slightly bell-like tone. Compare this to any arbitrary shaped piece of metal which produces a "clunk" when struck. The sound of the bell plate depends strongly on its shape and even the most modest change in the symmetry (like snipping off a corner) or proportions will make it go clunk when struck.

How it works: 

Why does a particular shape ring so well,...

What it shows:

The effect of length, tension, diameter, and kind of material on the pitch of a vibrating string is demonstrated. One may also show the harmonics of a vibrating string.

How it works:

The sonometer is a long hollow wooden box along the top of which are stretched one or more strings rigidly attached to the box at one end, with provision at the other for changing their tension. If there is just one string, it's known as a monochord. The monochord illustration is from John Tyndall's book entitled Sound, (...

Change pitch of organ pipes by changing sound velocity.

What it shows:

At a constant temperature, the speed of sound in a gas c, is dependant on the molecular weight of the medium

where γ, R, T are constants

Helium's low molecular weight results in a...

A high-pitched alarm on the end of a rope is whirled about the head.

What it shows:

Doppler shift of sound emitted by an object moving in a circular orbit, with the pitch clearly changing as the object move towards, away or perpendicular to the line of the observer. Useful as an analogy to the redshift and blueshift of spectral lines from a rotating astronomical source such as a planet or binary star system.

How it works:

We have a Powerhorn™ Security System buzzer attached to a 1.5m length of nylon cord. Swing it in a...

Plastic Wiffle Ball with built-in shriek to throw past (or at) your audience.

What it shows:

Waves emitted from a moving source are Doppler shifted to higher frequencies when moving toward the observer, and shifted to lower frequencies when moving away. This audio demonstration is also a useful analog to the optical red shift and blue shift exhibited by astronomical sources moving relative to the Earth.

Sound pressure level of a fire bell decreases by 6dB when distance is doubled.

What It Shows

The intensity of sound waves emanating from a point source changes inversely as the square of the...

A pulse of sound gets "inverted" when reflecting off the open end of a pipe, but does not get inverted when reflecting off the closed end.

Balloons filled with helium, CO₂, or SF₆ act as diverging and converging lenses, respectively.

What it shows:

A balloon, filled with a gas different from air, will refract sound waves. A gas denser than air turns the balloon into a converging lens and a lighter gas makes it a diverging lens. An air-filled balloon has little effect.