Physics Chapter 22 mastering physics
What happens to electrons in any charging process?
Electrons transfer from one place to another.
Part 2 of part A of: charge distribution on a conducting shell. A large positive charge inside the shell is roughly 16 times that of the smaller charges shown on the inner and outer surfaces of the spherical shell. Which of the following figures best represents the charge distribution on the inner and outer walls of the shell? (Figure 1)
1
The charge inside a conductor part A: What is the total surface charge q subset int on the interior surface of the conductor (i.e., on the wall of the cavity)?
-q
The charge inside a conductor, part b: What is the total surface charge of q subset ext on the exterior surface of the conductor?
+q
How much energy is given to each Coulomb of charge that flows through a 1.5 V battery?
1.5 joules
Two conducting spheres are each given a charge Q. The radius of the larger sphere is three times greater than that of the smaller sphere. If the electric field just outside of the smaller sphere is E subset zero, then the electric field just outside the larger sphere is
1/9 E subset 0
PhET part G: Consider a point 0.5 m above the midpoint of the two charges. As you can verify by removing one of the positive charges, the electric field due to only one of the positive charges is about 18 V/m. What is the magnitude of the total electric field due to both charges at this location?
25 V/m
Part A of: charge distribution on a conductor with a cavity
3
PhET charges an electric potential part B: What is the voltage 3 m away from the charge?
3
Part A of: charge distribution on a conducting shell The positive charge is equal to roughly 16 of the smaller charges shown on the surfaces of the spherical shell. Which of the pictures best represents the charge distribution on the inner and outer walls of the shell? (figure 1)
4
PhET tutorial: charges and electric potential part A: Using the voltage meter, you should find that one meter away from the charge, the voltage is 9 V. What is the voltage to meters away from the charge?
4.5
how does 1 coulomb of charge compare with a charge of a single electron?
A coulomb of charge is the charge associated with 6.25×10 to the 18th power electrons.
What is a positive ion? What is a negative ion?
A positive ion is a neutral atom that has lost one or more electrons. A negative ion is a neutral atomthat has gained one or more electrons.
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.
What is meant by saying that charge is quantized?
All charged objects have a charge that is an integer multiple of the charge of an electron.
How does the charge of one electron compared to that of another electron? How does it compare with the charge of a proton? How do the masses of protons and electrons compare?
All electrons have the same charge. Electron charges equal and opposite to the proton charge. A proton has 1800 times the mass of an electron.
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.
PhET charges in electric potential part C: Play several E field sensors at a few points on different equipotential lines, and look at the relationship between the electric field and the equipotential lines. Which statement is true?
At any point, the electric field is perpendicular to the equipotential line at that point, and it is directed toward lines of lower voltages.
Why are materials such as glass and rubber good insulators?
Electrons are tightly bound to their atoms, making them poor conductors of heat.
Why is there no electric field in the center of a charge 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.
Electric charge can be transferred from one conducting body to another_________
By both contact and closeness
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.
PhET part H: Make an electric dipole by replacing one of the positive charges with a negative charge, so the final configuration looks like the figure shown below. The electric field at the midpoint is
Directed to the right.
PhET part D: If the field strength is E = 9V/m a distance of 1 m from the charge what is the field strength E a distance of 3 m from the charge?
E = 1 V/m
PhET tutorial Chargers and electric potential part F: Now remove the negative charge, and drag two positive charges, placing them 1 m apart as shown below. What is the voltage at the midpoint of the two charges?
Exactly twice the voltage produced by only one of the charges at the same point
PhET part C: The magnitude of the electric field 1 m away from the positive charge is______ The magnitude of the electric field 2 meters away
Four times
Give two examples of common force fields and name the sources of these fields.
Gravity fields made by mass, electric fields made by charge
What kind of charging occurs during thunderstorms?
Ice crystals are charged by friction and the ground is charged by induction.
What is an electric dipole?
In an electric dipole, positive and negative charges are separated on opposite sides of an object.
As in the video, we apply a charge +Q to the half shell that carries the electroscope. This time, we also apply a charge -Q to the other half shell. When we bring the two halves together, we observe that the electroscope discharges, just as in the video. What does the electroscope needle do when you separate the two-half shells again?
It does not deflect at all.
(Within the video question one) how will the Can react to the negatively charged rod?
It will roll toward the rod.
(within the video question two) How will the can react to the positively charged rod?
It will roll toward the rod.
Two glass marbles (one and two) each supported by a nylon thread, or rubbed against a piece of silk and then are placed near a third glass marble (three)also supported by a similar thread. Assuming that marble three has not been in contact with a piece of fabric which of the following statements best describes the situation when the three marbles are brought together? *To keep things simple in this tutorial we will ignore the effects of polarization and just focus on the overall charge of each object.
Marbles one and two repel each other but no interaction occurs with marble three.
What is meant by the conservation of charge?
Net charge cannot be created or destroyed.
Coulombs law is most similar to which of these laws?
Newton's law of gravity
The charge inside a conductor part C: What is the magnitude E subset int of the electric field inside the cavity as a function of the distance r from the point charge? Let k, as usual, denote 1/4 pi epsilon subset zero.
kq/r^2
PhET part I: Make a small dipole by bringing the two charges very close together, where they are barely touching. The midpoint of the two charges should still be on one of the grid point intersections (See figure below). Measure the strength of the electric field 0.5 m directly above the midpoint as well as 1 m directly above. Does the strength of the electric field decrease as 1 over distance squared? (1/r^2)
No, it decreases more quickly with distance.
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.
Part C: using the set up from the first question imagine that you briefly touch the negatively charged rod to the can (assume that this rod is conducting for the sake of effect). You then hold the two rods at equal distances on either side of the can. What does the can do?
Rolls toward the positively charged rod
Part A: Consider the situation in the figure below, where two charged rods are placed a distance d on either side of an aluminum can. What does the can do?
Stays still
Part b: Now consider the situation shown in the figure below what does the can do?
Stays still
When charges mutually repel and distribute them selves on the outer surface of conductors, what becomes of the electric field inside the conductor?
The Chargers arrange themselves to make the field inside the conductor zero.
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.
PhET part E: Remove the positive charge by dragging it back to the box at the bottom, and dragging negative charge blue towards the middle of the screen determine how the electric field is different from that of the positive charge. Which statement best describes the differences in the electric field due to a negative charge as compared to a positive charge?
The electric field changes direction (now points radially inward), but the electric field strength does not change.
PhET tutorial: charge and electric field part A: Which of the following describes the electric field produced by the positive charge?
The electric field is directed radially away from the charge at all locations near the charge.
PhET part F: Now, remove the negative charge, and drag two positive charges, placing them 1 m apart, as shown below. Let's look at the resulting electric field due to both charges. Recall that the electric field is a vector, so the net electric field is the vector sum of the electric fields due to each of the two charges. Where is the magnitude of the electric field roughly equal to zero (other than very far away from the charges)?
The electric field is roughly zero near the midpoint of the two charges.
PhET tutorial charges in electric potential part H: Make several equipotential lines similar to the figure below. Try to have your equipotential lines equally spaced in voltage. Then, use an E field sensor to measure the electric field at a few points while looking at the relationship between the electric field and the equipotential lines which of the following statements is true?
The electric field strength is greatest where the equipotential lines are very close together to each other.
Where is the energy stored in a capacitor?
The energy is stored in the electric field between the plates
PhET tutorial charges an electric potential part D: Equipotential lines are usually shown in a manner similar to topographical contour lines, in which the difference in the value of consecutive lines is constant. Clear the equipotential lines using the erase button on the voltage tool place the first equipotential line 1 m away from the charge. It should have a value of roughly 9 V. Now, produce several additional equipotential lines, increasing and decreasing by an interval of 3 V (e.g., one with 12 V, One with 15 V, and one with 6 V). Don't worry about getting these exact values. You can be off by a few tenths of a bolt. Which statement best describes the distribution of the equipotential lines?
The equipotential lines are closer together in regions for the electric field is stronger
Electric potential part C: What happens to a lamp when you take both ends of the wire connected to it and hold them to the same side of the 12 V terminal of battery, and why?
The lamp does not light up because there is no voltage difference applied across it.
Electric potential part D: What happens when you have a voltage difference between the two ends of the lamp, and why?
The lamp lights up because there is a voltage difference applied to it.
A glass marble is rubbed against a piece of silk. As a result the piece of fabric requires extra electrons. What happens to the glass marble? Check all that apply.
The marble has lost the same number of electrons acquired by the piece of silk. The marble acquires a positive charge and attracts a piece of silk.
(question with in the video) What will happen to the electroscope needle when I push the cages together?
The needle will discharge (return to a vertical position)
Which part of the atom is positively charged and which part is negatively charged?
The nucleus is positively charged and the electron cloud is negatively charged.
Why are metals good conductors of both heat and electricity?
The outer shell electrons in metals are free to move from atom to atom.
(Within the video) which electrode (if either) carries a greater charge (and hence will put more charge on electric scope)?
The pointed end
What is the most common net charge of an atom?
neutral
PhET part B: Now, let's look at how the distance from the charge affects the magnitude of the electric field. Select values on the menu and then click and drag one of the yellow E field sensors. You will see the magnitude of the electric field given in units of V/m (volts per meter, which is the same as newtons per coulomb). Place the E field sensor 1 m away from the positive charge (1 m is two bold grid lines away if going in a horizontal or vertical direction), and look at the resulting field strength. Consider the locations to the right, left, above, and below the positive charge, all 1 m away. For these 4 locations, the magnitude of the electric field is________
The same
The charge inside a conductor part D: What is the electric field E subset ext outside the conductor?
The same as the field produced by a point charge q located at the center of the sphere.
PhET tutorial Chargers and electric potential part E: Now, remove the positive charge by dragging it back to the basket, and drag one negative charge toward the middle of the screen. Determine how the voltage is different from that of the positive charge. How does the voltage differ from that of the positive charge?
The voltages become negative instead of positive and keep the same magnitudes.
What is the primary purpose of a lightning rod?
To prevent a fire caused by lightning
Electric potential part A: What is the flow current proportional to?
Voltage difference between the two ends of the wire
Electric potential, unlike electric potential energy is measured in units of
Volts
Electric potential part B: A pipe is filled with water, and there is a piston at each end. If you apply unequal pressure at the two pistons, which way will the water flow in the pipe?
Water will flow from the piston with the higher pressure to the piston with the lower pressure.
The charge inside a conductor part H: Electric field outside the conductor, E subset ext
Would change
The charge inside a conductor part E: The total surface charge on the wall of the cavity, q subset int
Would not change
The charge inside a conductor part F: The total surface charge on the exterior of a conductor, q subset ext
Would not change
The charge inside a conductor part G: The electric field within a cavity, E subset cav
Would not change
Most Adams normally have a net charge that is________
Zero
PhET tutorial Charges in electric potential part G: Now, make an electric dipole by replacing one of the positive charges with a negative charge, so the final configuration looks like the figure shown below. What is the voltage at the midpoint of the dipole?
Zero
Which particle has exactly one quantum unit of charge?
proton
A highly-charged party balloon is not dangerous when it _________.
contains little overall energy
When we say charge is conserved, we mainly mean that charge can be
transferred without loss like money in a bank
An electric field is basically
vector quantity
Which molecule is an example of a common electric dipole?
water molecule
The electric field inside the dome of a highly charged Van de Graaff generator is
zero
The net charge on a polarized molecule is normally
zero
The net charge on an energized capacitor is normally _________.
zero
