• for low cost
• Name LUO Xingkai & LIU Xiaobing
• Address Department of Physics, Guangxi Normal University, Guilin, 541004, P. R. China
• Phone ++86-773-5818071
• Fax ++86-773-5818071 or ++1- 503-907-7627(eFax Free number)
• E-mail ipe@public.glptt.gx.cn or xkluo@mailbox.gxnu.edu.cn
• for intro lab apparatus Name LIU Xiaobing, LIANG Weigang & LUO Xingkai

Apparatus Title: Cardboard Electroscope

Abstract

This giant electroscope is designed for both lecture demonstration and providing students with hands-on learning by making it. It is very sensitive to electric charge and very resistant to high humidity weather due to the proper treatment at some key parts.

• Support required for apparatus : No special need.
• Approximate size: 45 x 35 x 25cm^2
• Does this apparatus require Electrical Power? no
• Is this apparatus intended for use with an overhead projector? no
• Will you be present to set up your apparatus? yes
• When do you plan to set up your apparatus? Sunday, July 30 2-4:30 PM

Equipment required to construct apparatus:

Item Source Part number Cost

• A cardboard package box (20x30x40cm size) Discarded item N/A 0
• Styrofoam Discarded item N/A 0
• Two Drinking straw Grocery store $0.05
• A piece of aluminum foil (300x600mm2 size) Grocery store $0.10
• Two aluminum pipes (1mm thin, 10mm Ø and 200mm long) Hardware store $0.40
• A short rectangular aluminum pipe (1mm thin, 6mm long, 10x20mm2 cross section) Hardware store $0.20
• Two screws Hardware store $0.10
• A pin Discarded item 0
• A piece of plastic film Discarded item 0
• Total Cost $ 0.75

Sketch of the apparatus

Description

The cardboard electroscope uses a large cardboard package box and an indicator (pointer) made of aluminum foil wrapping on two drinking straws to show electric charge. A pin with both ends sharpen is penetrated through the midpoint of the indicator as its axis which is supported by two screws with a conoid hole at each of their one end. By adjusting the screws to vary its degree of tightness to the pin points, one can change the mechanical sensitivity of the indicator. The two screws are screwed on a hollow frame aslant cut from a rectangular aluminum pipe. The frame is connected with two aluminum rods both up and down. Another important part of the electroscope is the stopper made of styrofoam or wax to insulate the conducting rod and the case which is made of a cardboard package box. The cap on the top can be made of cardboard painted with carbon ink. All these features make the electroscope very easy to make with ordinary materials. Moreover, the questions, such as why we can use cardboard as the case of the electroscope to replace the usually used metal one, what part needs to be well insulated to avoid discharging, etc., may possibly raised by students in making the apparatus. This will certainly promote thinking in depth about the physics background involved.

Apparatus Title: A Ripple Generator Using Air Blowing Driven by a Loudspeaker

Abstract

The ripple generator uses air blowing driven by a loudspeaker to generate wave on the water. Covering the loudspeaker with a gasket and plastic board forms a chamber in which the air pressure will fluctuate with the vibration of the loudspeaker's diaphragm. The current in such a chamber is then reduced to blow the water and generate water waves.

• Support required for apparatus No special need.
• Approximate size: 40 x 30 x 20cm2
• Does this apparatus require Electrical Power? yes
• Is this apparatus intended for use with an overhead projector? no
• Will you be present to set up your apparatus? yes
• When do you plan to set up your apparatus? Sunday, July 30 2-4:30 PM

Equipment required to construct apparatus:

Item Source Part number Cost

• A loudspeaker (100mmØ) Electronic store $6.00
• Two rubber pipes (each 8mm Ø and 500mm long) Medical material store $0.40
• Two ball pen tube Discarded item 0 Two plastic pipe (each 60mm long, one 20 mm Ø and another 18mm Ø) Discarded item 0
• A water trough for using on overhead projector (300x300mm2 size)
• Made from plastic glass $6.00
• Basic Function Generator PASCO SE-9698 $ Total Cost $

Sketch of the apparatus

Description

The Ripple Generator uses fluctuant air blowing driven by a loudspeaker to transmit, via air blowing tubes, the oscillations of the loudspeaker's diaphragm to the surface of the water. It can be used to demonstrate wave propagation, interference and some other experimental phenomena. By covering the loudspeaker with a gasket and plastic board as shown in Fig. 2, an air chamber is formed in which the air pressure will fluctuate with the vibration of the loudspeaker's diaphragm. Then, using air in such a chamber to blow the water will generate water waves. The frequency generator should have a frequency range from 1 Hz to 100 Hz and the SE-9698 Basic Function Generator made by PASCO is suitable for the experiment. However, we made a special frequency generator for this experiment with very low cost. Fig. 4 shows the circuit arrangement.