Chapter 19: Electric Charges, Forces, and Fields
Suppose E = 10 N/C. What force does a charge of 1 C feel?
-10 N
A charge of 2C?
-20 N
Why?
-A's electric field is stronger nearby, so bringing B closer would mean object B would need to shield a large E external (due to A from its interior) -this would require a larger E induced -this means that MORE charge polarization would need to occur in object B -once half of that charge polarization is removed by grounding, it would leave a larger net charge on B
What happens after B is disconnected (before A is taken away)?
-B will wind up with a net charge -After A is removed, this excess charge distributes itself across the surface to maximally repel in the volume available
If the force needs to be upwards, the field must be...?
-DOWNWARD (towards a theoretical negative charge)
Therefore, if you get far enough away from the conductor, what will the relationship between E net and E external?
-E net will be approximately that of E external alone (to the left in this instance)
What are the SI units of the electric charge?
-N/C
Describe how PVC becomes charged
-PVC becomes negatively charged
Why?
-Q and E are directly proportional
Two identical spheres are made of conducting material. Initially, sphere 1 has a charge of +35Q and sphere 2 has a net charge of -21 Q. If the spheres are not brought into contact, what is the final charge on sphere 1? Explain.
-The net charge of the two-sphere system is +35Q - 21Q = +14Q -when the spheres are brought into contact, this charge will be shared equally between the two spheres, giving each a charge of 7Q
In the world of electrostatics, force is a property that can act on...?
-a charge
Why?
-a conductor can completely cancel off an external electric field inside it with its own induced field (via mass electron migration). it leaves a net electric field of zero inside of the conductor--this is known as complete shielding. -an insulator can only partially cancel off an external field inside it with its own induced field (via electrons moving more towards one side of nuclei). it leaves a net electric field of greater than zero (but not las large as the external field) inside of the conductor--this is known as partial shielding. -hence, even though the external field is stronger outside of the conductor, the net electric field inside is less (zero)--complete shielding of a stronger field is still less than partial shielding of a weaker field
We have learned that shielding works in one direction only. What specifically does this mean?
-a conductor shields its interior from external fields, but it does not shield the external world from fields within it
The electric field is a property that can act on...?
-a given space
What is meant by *within* a conductor?
-a location in the actual material of the conductor, as opposed to a location in a cavity within the material
What is an insulator?
-a material that does not respond to an electric field and completely resists the flow of electric charge.
What is a counductor?
-a material which allows electric charges to move about more or less freely
What is a semiconductor?
-a material with electrical conductivity intermediate in magnitude between that of a conductor and an insulator -semiconductors can be fine-tuned to display almost any desired degree of conductivity by controlling the concentration of the various components from which they are made
Describe the type of material that must be used for the object that is being charged (object B)
-a neutral conductor must be used
Similar to?
-a parallel plate capacitor
How does the proton compare in size to an electron?
-a proton is about 2000 times larger than the mass of the electron
Does charge polarization take a long amount of time or a short amount of time?
-a short amount of time
Does charge polarization involve a large number or a small number of electrons?
-a small number of electrons
What is an electrostatic system?
-a system at which all electric charges are at rest
What is an electric dipole?
-a system of equal and opposite charges separated by a nonzero distance
What is C?
-a unit of charge referred to as the coulomb
What does charging by induction provide?
-a way to transfer charge without ever touching objects together
Once the charges have settled into equilibrium, the only remaining pull on them can be...?
-against the inner surface of the conductor (where they cannot go-they can't jump off the object)
Describe how a lightning rod works
-air molecules are more likely to be torn apart near the tip of a lightning rod where the electric field is the strongest
Describe how lightning is created
-air molecules have electrons and protons -air molecules are polar, or have an induced polarity -given a positively-charged cloud and a negatively-charged earth, the protons in the air molecule are attracted to the ground while the electrons are attracted to the cloud -if the forces attracting the protons to the ground become stronger than the forces attracting electrons to the clouds, the air molecules split in half...thus causing a lightning strike
Since electrons always have a charge e-, and protons always have a charge of e+, what follows?
-all objects must have a net charge that is an integer multiple of e
What occurs when excess charge is applied to a conductor with one or more cavities?
-all the charge ends up on the exterior surface, and none on the internal cavities
What is the direction of the force in Coulomb's law?
-along the line connecting the two charges
What does this system bear a strong resemblance to?
-an electric dipole (a system of equal and opposite charges separated by a nonzero distance_
What is created?
-an electric field
Suppose an uncharged conductor is brought into a uniform electric field that points to the left. Inside the conductor, charge polarization produces..?
-an induced electric field
What does this create?
-an induced negative charge on one half of the sphere and a positive charge on the other half
What will be produced?
-an induced positive charge on the near side of the sphere, and an induced negative charge on the far side
If you take a charge and divide by e, what should this result in?
-an integer
What is this referred to?
-as grounding the sphere
At what angle do electric field lines contact insulator surfaces?
-at angles less than ninety degrees
At what angle do electric field lines contact conductor surfaces?
-at right angles
Describe the direction in which electric field lines contact conductor surfaces
-at right angles
Why?
-because the electrons are firmly wedged up against the surface of the conductor
Why?
-because the net electric field has no parallel component
Why?
-because the net external electric field is decreasing
When should B be disconnected to the ground?
-before A is taken away
Describe the similarities between coulomb's law and newton's law of gravity.
-both laws depend on the product of specific properties of objects involved -both forces decrease with increasing distance as 1/r^2
How will the conductor and the insulator react when placed in their respective electric fields?
-both will remain stationary
An electron of charge -e orbits a helium nucleus of charge +2e. Is the force exerted on the helium nucleus by the electron greater than, less than, or the same as the force exerted on the electron by the helium nucleus? Explain.
-by Newton's third law, the forces exerted on the electron and the nucleus are equal in magnitude and opposite in direction
What does this result in?
-charge polarization
Why?
-charge polarization will occur in both the conductor and the insulator -if the external field is perfectly UNIFORM, then the two sides of the charge polarization feel an equal and opposite force and the net force is zero -neither object would feel any net force and would not move
Suppose a neutral conductor is placed in a non-uniform electric field. Describe what happens.
-charges will polarize -conductor will experience net force towards the charge
Describe the differences between charging by induction and charging by contact.
-charging by induction does not require contact between two objects, whereas charging by contact does -when an object is charged by induction, the sign of the charge the object acquires is opposite to that of the object used to do the charging -charging by contact gives the object being charged the same sign of charge as the original charged object
Describe static cling
-clothes rub against each other in the dryer, transferring charge -objects will have a net charge when they are removed from the dryer -objects will then be attracted to neutral objects through charge polarization
What purpose does connecting object B to the ground serve?
-connecting object B to the ground provides access to a sink/source of electrons
What equation describes the electrostatic force between these charges?
-coulomb's law
What does this do?
-cuts off access to the sink/source of electrons
The electric field is greatest as distance to the point charge...?
-decreases
What is the next step?
-disconnect object B from the ground
In what direction do the protons feel a force?
-downstream, away from the positive charge
True or false: electric field lines can intersect? Why?
-electric field lines cannot intersect -by definition, electric field lines are always tangent to the electric field -since the electric force, and hence the electric field, can point in only one direction at any give location, it follows that field lines cannot intersect -if they did, the field at the intersection point would have two conflicting directions
Under normal conditions, the electric field at the surface of the Earth points downward, into the ground. What is the sign of the electric charge into the ground?
-electric field lines point in the direction of negative charges -therefore, we conclude that the charge on the Earth is negative
At this point, is the sphere positively charged, negatively charged, or electrically neutral?
-electrically neutral
Describe how this occurs
-electrons and protons are held together within individual atoms -electrons become concentrated on one side of the atom, and move upstream towards the electric field (taking the protons with them) -asymmetric charge distribution then occurs, and the object becomes charge polarized
Describe the first step of charge polarization
-electrons move upstream, induced electric field is created
What is the effect of grounding the sphere?
-electrons repelled by the charged rod enter the ground
If object A is negative, what happens when B is connected to the ground?
-electrons travel from object B into the ground
If object A is positive, what happens when B is connected to the ground?
-electrons travel from the ground into object B
At a certain point, what will occur?
-electrons will stop moving upstream
Why not?
-electrons would move until the parallel component of the electric field was canceled
Describe how excess charge placed on a conductor is distributed
-excess charge placed on a conductor distributes itself uniformly on the surface of the conductor
What phenomenon does this help to explain? Why?
-explains the phenomenon of static cling -->neutral object of finite size can be attracted to a charge object, if placed in a non-uniform electric field
During this connection, electrons will flow...?
-from the ground into B
Suppose glass is rubbed against PVC. Describe how glass is charged.
-glass becomes positively charged
Describe the differences between coulomb's law and newton's law of gravity.
-gravity is always attractive, whereas electrostatic forces can be attractive or repulsive
Why?
-half of the charge polarization will be cancelled by grounding -the charges on A and B will neutralize each other -any remaining net charge can flow from anywhere on A & B and can neutralize with the ground
Does the field created have a vertical component? Why or why not?
-has no vertical component -the +y and -y components always cancel
What specifically does the electric field tell you?
-how many newtons of force are available per coulomb at a given spatial location
In astronomy, what role do gravity and electrical forces play?
-in astronomy, gravity rules -electric forces play hardly any role
A positive charge experience a force...?
-in the direction of E
A negative charge experiences a force...?
-in the opposite direction of E
The electric field is weakest as distance to the point charge...?
-increases
Why can't charge be uniformly distributed throughout the volume of the sphere?
-individual charges would experience a force due to other charges in the volume -since charges are free to move in a conductor, they will respond to these forces by moving as far from one another as possible; that is to the surface of the conductor
As r approaches zero, what does E approach?
-infinity
In contrast, insulators...?
-insulators have very few, if any, free electrons; the electrons are bound to their atoms and cannot move from place to place within the material
Describe the electric field near a sharp point on a conductor?
-intense electric field is generated
Why not?
-it gets weaker with distance
What is the total charge on the sphere?
-it remains zero
Consider an electrically neutral object. If this object is given a positive charge, does its mass increase, decrease, or stay the same. Explain.
-its mass decreases -this is because a positive charge is generally due to a loss of electrons, each of which has a small mass
If A is brought closer to B during this process (rather than further away), then the amount of charge that can be generated on B is...?
-larger
This is the operating principle of a...?
-lightning rod
What are semiconductors?
-materials that can be fine-tuned to display almost any desired degree of conductivity -->allow for electron flow to be controlled
What are conductors?
-materials with electrons that are mobile -electrons are shared amongst atoms -->a communist system!
What are insulators?
-materials with electrons that are not mobile -electrons are owned by individual atoms -->a capitalist system!
An electron and a proton, initially separated by a distance d, are released from rest simultaneously. The two particles are free to move. Where do they collide?
-near the initial position of the proton
The atom that receives an extra electron becomes a...?
-negative ion
Can net electric field lines ever cross? Why or why not?
-net electric field lines can never cross because every location in space must have a single unique direction for the net electric field -this points in the direction a positive charge would feel a net force if placed there
What is the net force? Why?
-net force equals zero -due to the fact that the force felt by the protons and the force felt by the electrons cancel
Can insulators be charged by induction?
-no
Do we expect the rod's electric field to be uniform?
-no
Is Fnet equal to zero?
-no
Is this induced electric field enough to cancel E external?
-no
Is there an absolute correspondence between charge and number of electric field lines?
-no -electric field lines are only a sampling
The force experienced by charge 1 at point A is different in direction and magnitude from the force experienced by charge 2 at point B. Can we conclude that the electric fields at points A and B are different? Explain.
-no -the direction of the forces might be different simply because the charges are different -the magnitude of the forces might be different simply because the magnitudes of the charges are different
Does it matter whether or not the object is a conductor or an insulator?
-no it does not (this only impacts the degree of polarization).
When an object that was neutral becomes charged, does the total charge of the universe change?
-no, the amount of total charge in the universe never changes
Do the bulk of electrons in a conductor have any idea that an external electric field exists? Why or why not?
-no, they do not -because the external electric field is cancelled by the induced electric field -the majority of the electrons are perfectly shielded from the outside environment
What are most insulators?
-non-metallic substances
Are the effects of E induced uniform or non-uniform?
-non-uniform
Note that it is important for the field to be...?
-non-uniform
Conductor A (positively charged) is brought nearby to conductor B (initially uncharged). We will use object A to charge object B by induction. Which object needs to be connected to ground (at some time in the process) in order for this to work?
-object B
Describe the type of material that must be used to induce charge (object A)
-object can be an insulator or a conductor
What is this known as?
-partial chielding
What type of shielding thus occurs?
-partial shielding
What is this called?
-perfect shielding
What is this phenomenon known as?
-perfect shielding
Therefore, in what direction does the field always point?
-perpendicular to the plate
What is coloumb's law stated in terms of?
-point charges
If, during an otherwise correct procedure, B was disconnected from ground only after A was taken far away, then the net charge on A would end up as...?
-positive
Describe the components/set-up of an infinite parallel plate capacitor?
-positive charge is uniformly spread over one plate -negative charge is uniformly spread over another plate -the two plates are placed parallel to each other
An atom that loses an electron becomes a...?
-positive ion
At this point, is the sphere positively charged, negatively charged, or electrically neutral?
-positively charged
Near a positive charge, field lines point...?
-radially away from the charge
Suppose a negative charge is at the origin. In what direction is the electric field directed?
-radially inward
Near a negative charge, field lines point...?
-radially inward toward the charge
If a charge q at the origin is negative, in what direction does the field point?
-radially inward towards the charge
Suppose a positive charge is at the origin. In what direction is the electric field directed?
-radially outward
If a charge q at the origin is positive, in what direction does the field point?
-radially outward from the charge
What does the induced electric field result from?
-results from those few electrons that migrate towards the external electric field, thus resulting in charge polarization
Suppose an uncharged insulator was brought into the same electric field that points to the left. The insulator will induce its own electric field that points to the...?
-right
How does rubbing a piece of amber with fur give amber a charge?
-rubbing fur across a piece of amber results in the transfer of charge from the fur to the amber
An extension of this dea explains what phenomenon?
-shielding
Why?
-since the charge polarization is able to shield the interior of the insulator somewhat, but not fully, from the external field
Why?
-since the ground is a fairly good conductor of electricity -since the Earth can receive or give up practically unlimited numbers of electrons
On an object of finite size (not a point charge), the two halves of the charge polarization are in two different...?
-spatial locations
What does this phenomenon explain?
-static cling
How?
-temporary adhesion bonds form between the two objects -glass donates electrons to the PVC -when glass and PVC are pulled apart, some electrons stay on the PVC -->thus, glass becomes positively charged and PVC becomes negatively charged
Describe the orientation of the net electric field just outside of the insulator nearby its surface.
-the E net is not bent as far away from its original direction -the conductor polarizes enough charge until the net field is bent perpendicularly to the surface, whereas an insulator does so more feebly and bends it only slightly towards that direction
On a microscopic level, what is the difference between conductors and insulators?
-the atoms in conductors allow one or more of their outermost electrons to become detached
Suppose a charge is placed on a sphere that is a conductor. How does this charge distribute itself on the sphere when it is in equilibrium?
-the charge concentrates on the surface -(excess charge placed on a conductor, whether positive or negative, moves to the exterior surface of the conductor)
Based on the materials listed in table 19-1, is the charge of a rubber balloon likely to be positive or negative?
-the charge of the rubber balloon is likely to be negative
They weaken with distanced from...?
-the conductor
As Q increases, what is the effect on the electric if r remains constant?
-the electric field increases
Why?
-the electric field that the electrons experience is greater than the electric field experienced by the protons
WHy is the opposite true in atomic systems?
-the electric force is greater than the gravitational force by a factor of 2.26 * 10^39
Suppose a negatively charged rod is brought close to an uncharged metal sphere without touching it. How will the electrons in the sphere behave?
-the electrons will be repelled
What will the impact on their relationship with protons be?
-the electrons will leave behind their protons, leaving the protons without a buddy!
What would happen if B is disconnected after A is taken away...?
-the electrons would flow back into the ground, due to the fact that they would have no reason to stay on object B -this would leave object B neutral -(the presence of object A nearby attracts and therefore holds the other half of the charge polarization on object B)
Within insulators, what is the induced electric field limited by?
-the extent of charge polarization
As a result?
-the external world can experience a force due to induced charges within the cavity of a conductor
Describe the field and the field lines as they approach the charge
-the field becomes more intense; the field lines move closer together
When drawing an electric field map, the field lines should be more dense where...?
-the field lines should be more dense where the electric field has a greater magnitude
What does this mean?
-the field points in a single direction--perpendicular to the plate--and its magnitude is independent of the distance from the plate
Suppose an uncharged, conducting metal sphere is placed in an electric field. In what direction does the field move charges within the sphere?
-the field tends to move negative charges towards the electric field
With this in mind, why is the object attracted to the negatively charged rod?
-the force of attraction to half the charge polarization (on the "near" side of the object) will be stronger than the force of repulsion to the other half (on the "far side")
What is one of the key differences between the force of gravity and electrical force?
-the force of gravity is always attractive, whereas the electric force can be attractive or repulsive
What does the induced electric field counteract?
-the force of the external electric field
As a result, what decreases?
-the force of the net electric field
What is the definition of the electric field?
-the force per charge at a given location
Why not?
-the force that the electrons feel upstream towards the electric field is greater than the force felt by protons downstream
Suppose that positive charge builds up in a cloud. What is the impact on the surface of the ground?
-the ground becomes negatively charged through charge polarization
Compare the induced charge on the sphere to the charge on the rod
-the induced charge on the sphere is opposite in sign to the charge on the rod
No more electrons move to the right when...?
-the induced field grows large enough to cancel the external field inside the conductor
A conductor and an insulator are each placed into their own region of uniform external electric field pointing to the right. However, the electric field into which the conductor is placed (of size E1) is stronger than the one the insulator is placed in (of size E2). Which object will have a larger net electric field inside of it?
-the insulator
Where do these field lines start and end?
-the lines start on the positive charge and end at infinity
Why?
-the mass of a proton is about 2000 times greater than the mass of the electron; therefore, the proton's acceleration is about 2000 times less than the electron's -as a result, the particles collide near the initial position of the proton
Since a coulomb is a significant amount of charge, what is the more common unit of charge?
-the microcoulomb, μC
When charge is transferred from one object to another, what is it generally due to?
-the movement of electrons
Why?
-the net electric force between neutral objects, such as the Earth and the Moon, is essentially zero because attractive and repulsive forces cancel one another; the electric force is very strong but cancels for neutral objects -since gravity is always attractive, the net gravitational force between the Earth and the Moon is nonzero
More generally, when charging an object by induction, the initially uncharged object will always end up with...?
-the opposite charge as the object used to charge it
What would result if an electric field contacted a conducting surface at an angle other than 90 degrees?
-the result would be a component of force parallel to the surface -this would result in a movement of electrons, and, hence, would not correspond to equilibrium
What is the next step?
-the rod can now be pulled away
What does the direction of the force depend upon?
-the sign of the charge
What is the next step in the charging process?
-the sphere is connected to the ground using a conducting wire
In contrast, what occurs when the sphere is charged y touch?
-the sphere will acquire a charge with the same sign as the charge on the rod
If the charge on the balloon is reversed, will the stream of water deflect toward or away from the balloon?
-the stream of water will deflect toward the balloon regardless of whether its charge is positive or negative, just as bits of paper are attracted equally well to a charged amber (-) or a charged glass (+) rod
What is the net electric field equal to?
-the sum of the external electric field and the induced electric field
What does the conservation of electric charge state?
-the total electric charge of the universe is constant -no physical process can result in an increase or decrease in the total amount of electric charge in the universe
In the OR, staff must take care not to create an electric spark. Should the operating-room personnel wear shoes that are conducting or nonconducting? Explain.
-their shoes should be conducting, so that any charge they transfer during walking can flow away into the ground
Explain why conductors can do "perfect shielding" while insulators can only do "partial shielding."
-there is only so much that atomic re-orientation can cancel -there is no full access to massive amounts of free electrons as in a conductor
Where do these field lines start and end?
-these lines start at infinity and end on a negative charge
Suppose a neutral conductor is placed in a uniform electric field. How will electrons react?
-they move towards the positive charge generated by the electric field
Why?
-they will be repelled by the existing electron density that is building upstream
Why?
-this creates imbalanced forces that give rise to the attraction
An object with a negative charge experiences an upward electrical force due to a uniform electric field equal in magnitude to its weight. This negative charge feels a force ________ the electrical field.
-this negative charge feels a force AGAINST the electrical field
How do those electrons that have not yet migrated react?
-those electrons are less inclined to charge polarize
What are the units of k?
-those that are required for the force F to have the units of newtons
What are electrically neutral objects?
-those with zero net charge
What is the next step?
-to remove object A from close proximity to object B
In what direction does the electric field point?
-to the right (away from the positive charges, towards the negative charges)
Describe the electric field within a parallel plate capacitor at points that are not near the edge of the plate
-uniform in both direction and magnitude
In what direction do the electrons feel a force?
-upstream, towards the positive charge
When drawing electric field maps, we give up what for what?
-we give up knowing the exact size/direction of the electric field at a given location in exchange for developing a more holistic view of the field
So what is E net?
-weakened, but still to the left
How does the object become charged?
-when an object becomes charged, it is because of a transfer of charge between it and another object
What is charging by induction?
-when an object is charged without making direct physical conduct
In addition to rubbing objects together, how may charge separation be created?
-when objects collide -->as an example, colliding crystals of ice in a rain cloud can cause charge separation that may ultimately result in lightening
Explain why a comb that has been rubbed through your hair attracts small bits of paper, even though the paper is uncharged.
-when the comb is rubbed through hair, it becomes charged -the comb then produces an unequal electric field -the electric field produced by the comb causes the paper to become polarized -the paper will feel a net force due to the fact that it is in an uneven electrical field, and will move towards the comb -the result is an attractive interaction between the comb and the paper
When does shielding occur?
-when the conductor is solid or hollow
When does electron migration stop?
-when the external electric field is equal to the induced electric field
What does the electric field help to explain?
-why/how two like charges move apart from each other
What is the next step?
-with the rod kept in place, the grounding wire is removed, trapping the net positive charge in the sphere
Can conductors be charged by induction?
-yes
Can insulators become charge polarized?
-yes
Do all electrons have the same electric charge?
-yes
Does charge polarization occur when conductors are placed in a uniform electric field?
-yes
Does charge polarization occur when conductors are placed in non-uniform electric fields?
-yes
Does the field created have a horizontal component?
-yes
Is the electric field constant in size?
-yes
When an object sits within a hole in a conductor, can perfect shielding still occur?
-yes
Would A still be positive in this instance?
-yes
Does the total amount of charge remain unchanged?
-yes -->at no time during the process is charge ever created or destroyed
A charged rod is brought near a suspended object, which is repelled by the rod. Can we conclude that the suspended object is charged? Explain.
-yes -if the suspended object were neutral, it would be attracted to the charged rod by polarization effects -the fact that the suspended object is repelled indicates it has a charge of the same sign as that of the rod
Describe the electric field outside of the plates?
-zero
If, during an otherwise correct procedure, A were accidentally touched to B while B is connected to the ground, then the net charge on A would end up as...?
-zero
The net charge on B would end up as...?
-zero
What is Fnet in this case?
-zero
What is the net external electric force within the conductor?
-zero
When electric charges are at rest, what is the electric field within a conductor equal to?
-zero; E = 0
What is 1 μC equal to?
1 μC = 10^-6 C
Describe the first two steps required to charge by induction
1. A is brought close to B 2. B is connected to the ground
What are the four rules for drawing electric field lines?
1. Point in the direction of the electric field vector at every point 2. Start at positive (+) charges or at infinity 3. End at negative (-) charges or at infinity 4. Make lines more dense where E has a greater magnitude. In particular, the number of lines entering or leaving a charge is proportional to the magnitude of the charge.
What is e equal to?
1.60 * 10^19 C
What value does k have?
8.99 * 10^9
A negative charge feels a force in the ______ direction as the electric field.
A positive charge feels a force in the OPPOSITE direction as the electric field.
A positive charge feels a force in the ______ direction as the electric field.
A positive charge feels a force in the SAME direction as the electric field.
What is the equation that describes the electric field?
E = F / q
Write the equation that describes the magnitude of the electric field a distance "r" from a point charge "q"?
E = k * |q|/r^2
What then is the relationship between the induced electric field and the external electric field?
E induced < E external
What is coloumb's law?
F = k(q1)(q2)/r^2
If we know the electric field vector E at a given point, what is the force that a charge q experiences at that point equal to?
F = qE
If there is a uniform field, there will be no _______ as these two forces will _______.
If there is a uniform field, there will be no FORCE as these two forces will CANCEL.
Suppose the object was neutral. It will experience ________ due to being in the rod's ________.
Suppose the object was neutral. It will experience CHARGE POLARIZATION due to being in the rod's ELECTRIC FIELD.
Suppose a negatively charged rod is brought near a suspended object, which is attracted to the rod. The suspended object must be ________ or ________.
The suspended object must be POSITIVELY CHARGED or NEUTRAL.
Therefore, Enet outside must be ______________ when it has achieved equilibrium.
Therefore, Enet outside must be PERPENDICULAR TO THE SURFACE OF THE CONDUCTOR when it has achieved equilibrium.
Therefore, there is no _________ component to the surface.
Therefore, there is no PARALLEL component to the surface.
How do you calculate the number of electrons in 1 C of charge?
divide 1 C by 1.60 * 10^-19 C/electron
What symbol denotes this electric charge?
e
What is the charge of one proton equal to?
e+
What is the charge of one electron equal to?
e-
