The circuits are built into large wood boards that mount easily onto an easel. The boards are labeled using conventional symbolism. Bulbs and batteries are easily removable--just be careful not to burn your fingers on the hot bulbs!
Why doesn't a bird sitting on a high-voltage wire get electrocuted? This demonstration addresses that question and serves as a model of the situation.
How it works:
The important concept conveyed is that there needs to be a voltage difference across a conducting medium for current to flow through the medium. In this situation the conducting medium is a bird sitting on a high-voltage wire. The voltage on the wire is the voltage of the whole length of wire with respect to the ground. Although the bird on the...
Insulating glass becomes a conductor of electricity when heated red-hot with a blowtorch. (m) (T+)
What it Shows
At room temerature, glass is almost as good an insulator as hard rubber. When heated to 1000 K, however, glass has a resistivity of less than 107 ohm-meters (Purcell1 fig. 4.8 pp 140). As glass becomes molten the once immobile ions are able to drift further between collisions under the influence of an applied electric field (Purcell pp 139). We can dramatically observe this decreased resistance using a blowtorch and a few incandescent...
Pure water is an electrical insulator. But provide an ionic compound in the form of salt, and you complete the circuit.
How it works:
A simple circuit with the mains supply connected to a 15W light bulb and two copper sheet electrodes (figure 1). The electrodes are placed in a 1500ml beaker containing distilled water. Distilled water is a very good insulator, with an autoionisation of 1:10-7 (the proportion of molecules in H3O+ + OH- form) it has a resistance of...
The electrical energy stored in a capacitor is converted to mechanical work, driving a motor and raising a weight.
How it works:
A motor 1 is mounted atop a 2.5m length of 2×4. As it turns, it raises a 1 lb mass on a string from the ground by wrapping the string around a spindle (figure 1). The motor is driven by the discharge of a 12800µF, 75V capacitor previously charged by a DC power supply. 2 A double throw switch allows a clean change-over from one circuit to the other. ...
How does shielding work? Is it a two-way street and work both ways? Can electric fields not penetrate metals? What's going on? This sequence of demonstrations addresses these questions.... Read more about Electrostatic Shielding
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.
A Van de Graaff generator will apply a charge to its dome and anything else in contact with the dome. Should that object be a person, they obtain a net surplus of charge (be it positive or negative). It is especially noticeable with hair, as each individual strand is repelled from every other and from the scalp.
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...
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...