Physics 123 Weeks 4 & 5 (Current, Resistance, & Circuits)
**WARNING** Any demos that require a supply can "short out" the power supply easily. Please be aware of your circuits, and include a contact key switch or resistor block when necessary.
Conduction
Conduction in Solutions
**WARNING** Exposed leads hazard.
When the two leads are placed in distilled water, the bulb will not light up. Slowly add small pinches of salt to the water until the bulb lights.
Conductors vs Insulators
By using the hand held high frequency generator, you can bring it close to various objects to investigate whether or not they are conductive!
Resistance and Resistors
The Mean Free Path and Resistance
By rolling marbles down a board with nails you can simulate an electron moving through a conductor. By varying the incline you can draw a parallel to varying the voltage! A rain stick can also be used to show the same concepts.
Circuit Elements
These are a variety of resistors, potentiometers, rheostats, and even small circuit boards that you can pass around to your students.
Resistance and Temperature
When the circuit is closed, a small light bulb will light up. There is an exposed filament in the circuit, and if you heat it up or cool it down you can vary the brightness of the small bulb as you influence the circuit's resistance through the filament.
Wire Resistances
This arrangement of wires can be used to introduce students to common wire materials, and can even be used to attain resistance readings for each material. ** If you choose to measure the resistances, please include a power resistor in series so that you do not short out the power supply.**
Joule Heating
**WARNING** A resistor block must be in series with PSU
When current passes through this thin ni-chrome wire the wire will begin to glow. Use a piece of paper and let the wire melt through it to show the effects of Joule heating.
Parallel & Series Circuits
Bulbs are wired so that you can easily switch between parallel and series configurations. These demos can be a great way to start a discussion as you introduce the concepts. Let your students make observations and use those to drive your lectures.
Batteries
Assortment of Batteries
Here is our assortment of various (dead) batteries that can be passed around to your students. Caution, as there may be some battery acid build up over time. Included is a cut open wet cell.