Phun with Electricity
In todays lab we will investigate a variety of subjects associated with electricity. Some of these phenomena you will have seen in class others will be new to you and hopefully you will be able to figure them out.
Part 1: Electrostatics: In this experiment we will use a device called an electroscope. Remove the cap from the top. Move the rod on your table near the ball on the top. What do you observe? Now vigorously rub the rod with the cloth provided on the table. Do this for a minute or so. Now move the rod near the top of the electroscope. What do you observe? Why does what you observe happen? Now place the metal cap back on and again rub the rod with the cloth. What do you observe now? What do you think is happening?
Part 2: A Hair Raising Experience: For this part we need a volunteer from the class. The volunteer will stand on a platform and place their hand on the dome of the Van de Graaff generator. The Van de Graaf generator romoves charge from the bottom of the device and moves this charge to the metal dome, the charge then goes to the surface of the dome. When the device is running what do you observe about our volunteer? Why does this happen?
Part 3: What conducts electricity? In this experiment you will use a very useful device that is called a digital voltmeter or what physics types call a DVM. This device can measure a variety of electrical quantities. Here we will use it to see what conducts electricity and what does not conduct. Turn on the DVM. On the DVM turn the knob to the area labelled OHM. Set the knob to the 200 ohm reading. With the metal ends of the black and red probes not touching what do you read on the DVM? This result of the DVM reading 1 tells you that the air between the probes does not conduct electricity. Now touch the ends together. What do you read? This number tells you that the probes will conduct electricity with a resistance of what you read. To determine if an object conducts electricity or not place both the black and red probes on the object. Make sure that the metal parts of the probes make good contact with the object and that the probes do not touch one another. Now pick a variety of objects around the lab and see what objects conduct and what do not and write these down. Just like the air objects that don't conduct will read 1 on the DVM. What do the objects that conduct have in common? What do the objects that don't conduct have in common?