Unit 3: Static Electricity Flashcards
What special property does this material have that makes it useful in a copy machine?
When selenium is in the presence of light, it has a very high conductivity. When it is in darkness, it has a very low conductivity.
An electroscope has been charged with a negative charge. An object with an unknown charge is brought close to the electroscope. The leaves of the electroscope come closer together. Does the object have a positive or a negative charge?
Positive. When electrons are attracted away from the leaves, they become less negative and move closer together.
Can one thundercloud contain both positive and negative charges?
In a thundercloud both positive and negative charges are contained in the same cloud.
A thundercloud has a negative charge, and an object on the ground has a positive charge. Will the lightning discharge be from the cloud to the ground or from the ground to the cloud?
Current always flows from negative to positive. If a cloud is negative and an object on the ground is positive, the lightning discharge travels from the cloud to the ground.
Why is static electricity considered to be a charge and not a current?
Static electricity refers to electrons that are sitting still and not moving.
If electrons are removed from an object, is the object positively or negatively charged?
If an object has a lack of electrons, it has a positive charge.
What is an electroscope?
An electroscope is a device used to determine the polarity of an object.
Name two devices used for lightning protection.
Lightning rods and lightning arrestors.
Why do static charges accumulate on insulator materials only?
Electrostatic charges are built up on insulator materials because insulators are the only materials that can hold the electrons stationary and keep them from flowing to a different location.
What type of material is used to coat the aluminum drum of a copy machine?
Selenium is a semiconductor material that changes its conductivity with a change of light intensity.
