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31 terms

Conestoga Physical Science Chapter 7

Study guide for chapter 7 test. (Electricity)
What is intra-cloud lightning?
lightning that occurs between the charged areas of two clouds, rther than one cloud and the ground. This happens 10 times moe often than cloud to ground lightning.
Why does a spark jump from your hand to the doorknob as you reach for the door after walking across a carpeted floor?
Your skin and the metal doorknob are conductors, so as you walk, electrons on your shoes repel each other, electrons spread out over your skin to your hand and jump a spark to the knob.
Explain why clothes stick together when they are removed from a dryer.
Some clothes lose electrons and become positively charged. Other clothes gain electrons and become negatively charged. Opposite charges attract.
How is electric current different from static electricity?
Electric current involves the flow of charge, whereas static electricity involves the accumulation of excess charge.
How do electrons flow in an electric circuit in terms of voltage difference?
Electrons flow from high voltage to low voltage.
Why does current generally involve the flow of electrons, but not protons?
Protons are locked deep in the nucleus of the atom and do not move. Electrons are in the outer part of the atom and are free to move around the nucleus.
Explain what a battery is.
Dry cells or wet cells connected in series that use a chemical reaction to create a voltage difference.
List two materials that are conductors and two materials that are insulators.
Conductors-copper, silver, aluminum
Insulators-plastic, rubber, wood, glass
What happens to the current in a device if the resistance of the device increases and the voltage difference stays the same?
According to Ohm's law, the current decreases.
what is a device designed to open an overloaded circuit and prevent overheating?
Circuit breaker
What is the equation to calculate electrical energy?
E=P x T
What is the correct relationship among power, current, and voltage?
P=I x V
Once source of constant electric current is a _________________________.
Dry cell
If the leaves of an electroscope spread apart, it indicates that________________________________________________________________.
the leaves of the electroscope have received a charge.
A static discharge differs from an electric current in that a static discharge_________________________.
lasts for only a fraction of a second.
The rate which an electrical device converts energy from one form to another is called___________________________.
Electrical power
A circuit that has two or more branches for electrons to follow is a ____________________________.
Parallel circuit
Electric charge that has accumulated on an object is referred to as _______________________________.
Static electricity
Resistance is measured in a unit called the ___________________.
The statement that current is equal to the voltage difference divided by the resistance is known as____________________________.
Ohm's law
A path that allows only one route for an electric current is called a________________________________.
Series circuit
___________________ is the tendency for a material to oppose the flow of electrons.
The unit of ________________ is the kilowatt-hour.
Electrical Energy
A _____________________ is a device used to keep electrical circuits from overheating.
The _______________________ rod forms the positive terminal of a dry cell.
The unit used to measure current is the __________________.
amperes or amps
Voltage difference is measured in ___________________________.
______________________ is a material that doesn't allow electrons to flow through it easily.
An insulator
The presence of a static electric charge can be detected by ____________________________.
An electroscope
A lightning bolt occurs when billions of ___________________________ are transferred at the same time.
The rearrangement of electrons on a neutral object caused by a nearby charged object is called charging by ___________________________.