28 terms

# Ch 22

###### PLAY
protons in the nucleus
The number of electrons that move about the nucleus of an electrically neutral atom is the same as the number of ____________________.
Electrons
To say an object has a negative charge is to say it has an excess of what kind of charges?
is transferred, but never created or destroyed.
To say that charge is conserved is to say that charge ____________________.
is normally zero with opposite charges on opposite ends
To say a substance is electrically polarized is to say that its net charge is ____________________.
induction
Charge polarization is normally produced by ____________________.
joules per coulomb, or volts
Electric potential is measured in units of ____________________.
very little energy on the balloon
Touch a 5000-V charged balloon and you're not harmed because, although the energy/charge ratio is high, there is ____________________.
Electric charge and mass generate an attractive force. However, charges only generate an attractive force if the two signs are different. Otherwise, for like charges, a repulsive force is generated
With respect to forces, how are electric charge and mass alike? How are they different?
The clothes have picked up charges (or "static electricity")
Why do clothes often cling together after tumbling in a clothes dryer?
So that any excess charge is transferred to the ground to minimze sparking.
Why are the tires for trucks carrying gasoline and other flammable fluids manufactured to be electrically conducting?
Lets pretend that the object touching the ball isnegatively charged. The negative charge forces all of the electrons in the ball to move down towards the leafs, giving them a negative charge. The tow leafs, which now have a negative charge, repel each other
An electroscope is a simple device consisting of a metal ball that is attached by a conductor to two thin leaves of metal foil protected from air disturbances in a jar, as shown. When the ball is touched by a charged body, the leaves that normally hang straight down spread apart. Why? (Electroscopes are useful not only as charge detectors, but also for measuring the quantity of charge: the more charge transferred to the ball, the more the leaves diverge.)
The electric force is stronger when the electron is closer to the nucleus
It is relatively easy to strip the outer electrons from a heavy atom like that of uranium (which then becomes a uranium ion) but very difficult to remove the inner electrons. Why do you suppose this is so?
The same
If electrons were positive and protons negative, would Coulomb's law be written the same or differently?
No, because the the charges interact without touching
Is it necessary for a charged body to actually touch the ball of the electroscope for the leaves to diverge? Defend your answer.
Theoretically the mass will change. However the mass of an electron is very small
Strictly speaking, when an object acquires a positive charge by the transfer of electrons, what happens to its mass? When it acquires a negative charge? Think small!
You can induce a charge on the other side of a conductor with a positively charged object. Consider a metal rod. If a positive charge is placed at one end, all of the positive charges are repelled to other other end. Or, the opposite end becomes positively charged
How can you charge an object negatively with only the help of a positively charged object?
The magnitude of the force is inversely proportional to the square of the distance. So if the distance is halfed, the force increases by a factor of 4, etc...
How does the magnitude of electric force compare between a pair of charged particles when they are brought to half their original distance of separation? To one-quarter their original distance? To four times their original distance? (What law guides your answers?)
The force doubles
Two equal charges exert equal forces on each other. What if one charge has twice the magnitude of the other. How do the forces they exert on each other compare?
Again, the electric field strength is inversely proportional to the square of the distance. If the distance is doubled, the strength will reduce by 1/4
Suppose that the strength of the electric field about an isolated point charge has a certain value at a distance of 1 m. How will the electric field strength compare at a distance of 2 m from the point charge? What law guides your answer?
The Earth has a negative charge
Measurements show that there is an electric field surrounding the Earth. Its magnitude is about 100 N/C at the Earth's surface and points inward toward the Earth's center. From this information, can you state whether the Earth is negatively or positively charged?
Under an intense electric field, the electrons have so much force that they ionize (or strip other electrons off of atoms) neighboring atoms. A domino effect occurs until a conductive path is established
If a large enough electric field is applied, even an insulator will conduct an electric current, as is evident in lightning discharges through the air. Explain how this happens, taking into account the opposite charges in an atom and how ionization occurs.
The electrostatic force (coulomb's force) makes it stick
If you rub an inflated balloon against your hair and place it against a door, by what mechanism does it stick? Explain.
The force and acceleration will be the same. However, the proton and electron will travel in opposite directions
If you place a free electron and a free proton in the same electric field, how will the forces acting on them compare? Their accelerations? Their directions of travel?
A proton has a positive charge
A gravitational field vector points toward the Earth; an electric field vector points toward an electron. Why do electric field vectors point away from protons?
The charge concentration at the corners will be much larger
Suppose that a metal file cabinet is charged. How will the charge concentration at the corners of the cabinet compare with the charge concentration on the flat parts of the cabinet?
If a lightning bolt strikes a car, the charge will reside outside, on the surface of the car
What safety is offered by staying inside an automobile during a thunderstorm? Defend your answer.
Increase the surface area of the plates
In order to store more energy in a parallell-plate capacitor whose plates differ by a fixed voltage, what change would you make in the plates?
No, because all of the charges reside outside, on the surface of the sphere
Would you feel any electrical effects if you were inside the charged sphere of a Van de Graaf generator? Why or why not?