Why does the gravitational force between Earth and the Moon predominate over electrical forces?
There is no electrical force between Earth and the Moon. The much weaker gravitational force only attracts
Which part of the atom is positively charged and which part is negatively charged.
Protons are positively charged and electrons are negatively charged
How does the charge of one electron compare with the charge of another electron? How does it compare with the charge of a proton?
All electrons have the same charge and mass. The charge of an electron is equal but opposite to the charge of a proton
What is most commonly the net charge of an atom?
Aero (an atom has as many electrons as protons)
What is a positive ion? A negative ion?
A positive ion has a net positive charge-it has lost one or more electrons. A negative ion, an ion with one or more extra electrons, is negatively charged
What is meant by conservation of charge?
Electric charge can neither be created nor destroyed
What is meant by saying that charge is quantized?
Whole number multiples of the basic charge
Name one particle that has exactly one quantum unit of charge?
An electron or proton has exactly one quantum unit of charge
How does one coulomb of charge compare with the charge of a single electron?
1 C is the charge associated with 6.25 billion billion electrons
How is Coulomb's law similar to Newton's law of gravitation? How is it different?
Both laws are inverse-square laws; Newton's law is attractive but Coulomb's law for electrical forces, unlike gravity, can be attractive or repulsive. Coulomb's law-product of 2 charges. Newton's law-product of 2 masses.
Why are metals good conductors both of heat and of electricity?
The outer shell electrons in metals are free to move from atom to atom.
Why are materials such as glass and rubber good insulators?
Electrons are tightly bound to their atoms, making them poor conductors of heat. The outer electrons belong to particular atoms
How does a semiconductor differ from a conductor or an insulator?
A semiconductor is neither a good conductor nor a good insulator - it has a middle range of resistivity. Fair insulator in pure crystalline form, excellent conductor when e- added or removed
What is a transistor composed of, and what are some of its functions?
A transistor is made of thin layers of semiconducting materials sandwiched together. It can be a switch, an oscillator, or an amplifier. Behaves as both conductor and insulator (thus on/off switch, up/down amplifier)
How does the flow of current differ in a superconductor compared with the flow in ordinary conductors?
Ordinary conductors have a small resistance to the flow of electric charge, but Superconductors have infinite conductivity (current flows forever)
What happens to electrons in any charging process?
Electrons transfer from one place to another.
What kind of charging occurs when you slide your body across a plastic surface?
Charging by friction occurs. Electrons are transferred when one object rubs against another. *same with socks on carpet!
What kind of charging occurs during thunderstorms?
Ice crystals are charged by friction and the ground is charged by induction. As warm water vapor rises in the air, it brushes against ice crystals high in the air above, producing a charge (friction).
What is the primary purpose of a lightning rod?
To prevent a fire caused by lightning. If sufficient charge does not leak from air to rod, charge will attract to the rod and direct to the ground instead of building.
In terms of net charge, how does an electrically polarized object differ from an electrically charged object?
An electrically polarized object can have zero net charge, while a charged object cannot have zero net charge. Polarized: one side of atom is more +, other side is more -. Charged: entire atom is either + or - charged.
What is an electric dipole?
In an electric dipole, positive and negative charges are separated on opposite sides of an object. Distribution of electric charge is not perfectly even.
Give an example of a common electric dipole?
Give two examples of common force fields and name the sources of these fields.
Gravity fields made by mass, electric fields made by charge
How is the direction of an electric field defined?
The direction of the field is the direction of the force on a positive test charge.
Why is there no electric field at the center of a charged spherical metal ball?
Because of mutual repulsion, mobile electrons in the conductor will spread out uniformly over the outer surface of the ball, so the force and the field on a test charge at the center is zero because opposing forces balance in every direction.
When charges mutually repel and distribute themselves on the surface of conductors, what becomes of the electric field inside the conductor?
The charges arrange themselves to make the field inside the conductor zero. (ex: in sphere, in car)
How much energy is given to each coulomb of charge that flows through a 1.5-V battery?
1.5 Joules. 1 volt = 1 joule/coulomb
A balloon may easily be charged to several thousand volts. Does that mean it has several thousand joules of energy? Explain.
No. Energy is voltage times charge, so you need a coulomb of charge to get several thousand joules of energy. Difference between electric potential energy and electric potential.
Where is the energy stored in a capacitor?
The energy is stored in the electric field between the plates.