Physics 2 Exam 2

If a hollow conducting sphere has an excess charge of -10mC, what is the electric field inside the sphere? 10 N/mC 10 N/C 0 N/C Not enough information

0 N/C

The unit of electric potential is the volt. What is 1V equal to? 1 N/C 1 J/C 1 C/N 1 C/J

1 J/C

What is the potential difference between one plate of a parallel plate capacitor and a point half way between the plates if the full potential difference between the plates is 5 V? 5 V 2.5 V 3.75 V 0 V

2.5 V

What is an electric dipole? An atom missing two electrons An atom with two extra electrons A neutral object with a separation between positive and negative charges, A molecule with loosely bound protons.

A neutral object with separation between positive and negative charges

What is needed in order for current to flow? Potential difference Complete circuit Potential difference and a complete circuit A very long wire

A potential difference and a complete circuit

The electron volt is A unit of charge A unit of energy A unit of electric potential A unit of electric field

A unit of energy

Which of the following is not a real physics field? Electric Gravitational Magnetic All are real fields None of these are real

All are real fields

How can charge be moved? Friction Contact Polarization All of the above

All of the above

The energy stored in a capacitor is equal to ½ C(ΔVC)^2 ½ Q^2/C ½ Q (ΔVC) All of the above

All of the above

The resistance of a wire to current flow depends on The cross-sectional area of the wire The length of the wire The material of the wire All of the above

All of the above

Which of these is a property of current? Causes light bulbs to glow Deflects compass needles Causes wires to get warm All of the above

All of the above

Electric fields Point from higher to lower potential Are perpendicular to equipotential lines Are stronger where the equipotential lines are closer together All of the above.

All of the above.

Which sequence describes how current is created? An electric field creates an electric potential which creates current. A current creates an electric potential which creates current An electric potential creates an electric field which creates the current An electric potential creates a current which creates an electric field.

An electric potential creates an electric field which creates the current

The author's analogy for a battery in a circuit is An escalator An elevator A waterfall A dam

An escalator

How are electric forces between several charged objects combined? Electric forces cannot be combined By adding the magnitudes of individual forces. By adding the individual vectors. There are no forces between charged objects.

By adding the individual vectors

The unit of capacitance, farad, F, is equal to V/C N/C C/V C/N

C/V

The unit of current is the ampere (amp) which is defined as J/s V/s C/s F/s

C/s

What is the difference between Coulomb's law for forces between charged objects and Newton's law of gravity? There is no difference other than the constants used. Gravity is attractive while charge forces are only repulsive. Charge forces are attractive while gravity is repulsive. Charge forces can be attractive or repulsive while gravity is only attractive.

Charge forces can be attractive or repulsive while gravity is only attractive

What does the law of conservation of charge mean? Charge is created when plastic is rubbed with wool Charge is destroyed when it is transferred. Charge is neither created nor destroyed when it is transferred. Charge is only created by neutral objects.

Charge is neither created nor destroyed when it is transferred

What type of energy does a battery use to cause charges to move? Gravitational potential energy Chemical energy Elastic energy Kinetic energy

Chemical energy

Electric fields are Created by charged objects altering the space around them A figment of a physicist's imagination A useful model but are not real Only found in empty space between the planets.

Created by charged objects altering the space around them

A parallel plate capacitor Creates an electric field by pulling electrons off of atoms in the air Creates a uniform electric field between two oppositely charged plates Creates a uniform electric field between two plates with the same sign charge Is not in this chapter.

Creates a uniform electric field between two oppositely charged plates

What is the convention for the direction of charge flow in the context of electric current? Current is the flow of negative charge Current is the flow of positive charge The current direction depends on the type of wire Current direction cannot be determined

Current is the flow of positive charge

The electric potential in a charged parallel plate capacitor Is the same throughout the capacitor Increases from the positive plate to the negative plate Decreases from the positive plate to the negative plate Does not exist

Decreases from the positive plate to the negative plate

What are the charge carriers in a metal? Protons Positive ions Negative ions Electrons

Electrons

What is the force on a charge Q in an electric field with strength E? F = Q/E F = E/Q F = QE F = 1/(QE)

F=QE

The electrical potential at a resistor is Higher at the end the current exits Higher at the end the current enters The same at both ends Depends on the current through the resistor

Higher at the end the current enters

How is the current, I, in a conductor related to the resistance, R, of the conductor and the potential difference across it, ΔV? I = R(ΔV) I = (ΔV)/R I = R/(ΔV) I = R(ΔV)/A

I = (ΔV)/R

Where is the energy stored in a capacitor? In the electric field In the positive plate In the negative plate In both plates.

In the electric field

What change would decrease the resistance of a wire? Increase the cross-sectional area Decrease the cross-sectional area Increase the length Maintain the length but put it in a coil

Increase the cross-sectional area

The electric potential energy of 2 charged objects with the same sign charge Increases as they are moved closer together Decreases as they are moved closer together Is constant regardless of the distance Is not discussed in the chapter.

Increases as they are moved closer together

The capacitance of a capacitor can be increased by Inserting a conductor between the plates Inserting an insulator between the plates Charging it in reverse. Increasing the distance between the plates.

Inserting an insulator between the plates

The electric field of a conductor with +3 nC of excess charge Does not exist Is parallel to the surface of the conductor Is perpendicular to the surface of the conductor Points toward the conductor.

Is perpendicular to the surface of the conductor

The energy stored in a capacitor Is proportional to the potential difference squared Is proportional to the potential difference Is proportional to the capacitance squared Can only be released slowly

Is proportional to the potential difference squared

The equilibrium position of an electric dipole in an electric field Is with the dipole moment in the opposite direction as the electric field. Is perpendicular to the electric field. Is with the dipole moment in the same direction as the electric field. An electric field has no effect on a dipole.

Is with the dipole moment in the same direction as the electric field

The electric potential inside a charged conductor in electrostatic equilibrium Is zero Is highest at a sharp corner Is lowest at a sharp corner Depends on the net charge of the conductor

Is zero

If you decrease the distance between two charged objects what happens to the force between them? It decreases It points in the opposite direction It increases It disappears when they get too close

It increases

The potential energy of a charged particle in an electric field is proportional to Its charge Its mass Its volume Its spring constant

Its charge

The electric field due to a point charge q is K(q/r) K(q^2/r^2) K(q/r^2) K(q^2/r)

K(q/r^2)

What is more dangerous, a large electric potential difference or a large charge transfer? Large electric potential difference Large charge transfer Electric potential difference and charge transfer are equally dangerous Neither are dangerous

Large charge transfer

The resistivity of a good conductor is Higher than for insulators The same for all conductors Lower than insulators Depends on the shape of the conductor

Lower than insulators

What type of charge can move within a conductor? Negative Positive Positive or negative, depending on why they are moving Charges can't move in a conductor

Negative

The power dissipated by a resistor can be written as I2(ΔVR) IR2 (1/R2)(ΔVR) None of the above

None of the above

Electric field vectors Are not useful Point toward positive charges and away from negative charges Point toward negative charges and away from positive charges Point away from positive and negative charges

Point toward negative charges and away from positive charges

What is the direction of the electric field in a charged parallel plate capacitor? Negative to positive Positive to negative Not enough information There is no electric field in a parallel plate capacitor.

Positive to negative

A battery supplies which 2 things? Potential difference and resistance Energy and resistance Energy and capacitance Potential difference and energy

Potential difference and energy

What is the source of the energy that made the foil ball bounce between the plates of the parallel plate capacitor? Kinetic energy of the foil ball. Thermal energy of the plates warmed by the power supply. Potential energy of the separated charges on the plates. Gravitational potential energy of the foil ball.

Potential energy of the separated charges on the plates.

A lightning rod is intended to Attract lightning and provide it a safe path to the ground. Prevent a lightning strike by ionizing the air around it. Attract lightning and absorb the charge. Prevent a lightning strike by increase the amount of charge on the building.

Prevent a lightning strike by ionizing the air around it

The potential difference between plates of a parallel plate capacitor is Proportional to the capacitance Proportional to the charge on the plates Proportional to the charge squared The same no matter what

Proportional to the charge on the plates

In a circuit, how does the current before the resistor compare to the current after the resistor? It depends on the composition of the resistor Higher before the resistor Higher after the resistor Same before and after the resistor

Same before and after the resistor

A potential difference can be created by Moving a charged object around Separating positive and negative charges Placing positive and negative charges as close together as possible It's not created. It is just a mathematical model.

Separating positive and negative charges

The capacitance of a parallel plate capacitor only depends on The distance between the plates and the charge on the plates The area of the plates and the distance between the plates The area of the plates and the potential difference The charge on the plates and the area of the plates.

The area of the plates and the distance between the plates

What happens to the current in the Play-doh when the shape is changed so that it is longer and thinner? The current increases The current remains the same The current decreases The current fluctuates wildly

The current decreases

Kirchhoff's junction law states The current entering a junction is larger than the current exiting the junction The current entering a junction is smaller than the current exiting the junction The current entering a junction is equal to the current exiting the junction The amount of current exiting a junction depends on the number of paths.

The current entering a junction is equal to the current exiting the junction

What happens to the electric field in the capacitor as the charge, Q, stored in it increases? The field increases as Q. The field decreases as 1/Q. The field increases as Q2. The field decreases as 1/Q2.

The field increases as Q

You measure a force between 2 charged objects. What happens to that force if the distance between the objects is reduced to ½ of what it was? The force is increased by a factor of 2. The force is increased a factor of by 4. The force is decreased by a factor of 2. The force is decreased by a factor of 4.

The force is increased a factor by 4

A charged object moves freely in an electric field. As its electric potential energy decreases what can be said about its kinetic energy? The kinetic energy increases The kinetic energy is constant The kinetic energy decreases There is not enough information to say anything about the kinetic energy.

The kinetic energy increases

Which plate in a charged capacitor has the higher electric potential? Both plates are at the same potential The positively charged plate The negatively charged plate It depends on the shape of the capacitor

The positively charged plate

Each pair of leads used to make an electrocardiogram measure The charge flowing between the leads The potential difference between the leads The rate of blood flow between the leads The difference in the sound of the heartbeat.

The potential difference between the leads

How are the direction of electric field lines related to equipotential lines? They are not related They are parallel They are perpendicular They never cross

They are perpendicular

Capacitors are useful because They are the only way to store electrical energy They can charge quickly and release the energy slowly They can charge slowly and release the energy quickly None of the above

They can charge slowly and release the energy quickly

Which has a larger magnitude charge, proton or electron? Proton because it is more massive. Electron, because it moves more in the atom. Electron because it is responsible for chemical bonds They have the same amount of charge, but opposite signs.

They have the same amount of charge, but opposite signs

When the current passed through 2 identical bulbs connected one after the other, which one was brighter? The first one The second one They alternated They were the same

They were the same

What is the electric potential energy of 2 charged objects q1 and q2, when they are separated by a distance r? U = K (q1*r)/q2 U = (q1*q2)/(K*r) U = K (q1*q2)/r U = (q1*q2*r)/K

U = K (q1*q2)/r

What direction is the force on an electron due to Earth's electric field? Earth doesn't have an electric field Up Down Toward the north pole

Up

The electric potential, V, of a point charge is related to the distance, r, from that charge as V ∝ 1/r V ∝ 1/r^2 V ∝ r V ∝ r^2

V ∝ 1/r

Another term for the electrical potential difference between 2 points (like a battery) is Amperage Conductivity Voltage Current

Voltage

What is true about the work, W, done on a book, and the change in gravitational potential energy, ΔU, of a book when you lift it at a constant speed? W>ΔU>0 W<ΔU<0 W=ΔU>0 W=ΔU<0

W=ΔU>0

Electric field lines are closer together When the electric field is stronger When the electric field is weaker When the electric field is positive When the electric field is negative

When the electric field is stronger

In the model of an ideal wire in a circuit Wires contribute 1 Ω of resistance Wires have 0 Ω of resistance Resistance of the wire depends on its length The wire carries no current

Wires have 0 Ω of resistance

Does the shape of a charged conductor affect the electric field around it? No because the field inside is zero. No, because the charge is evenly distributed. Yes. The field is stronger where the shape is more pointed. Yes. The field is stronger where the shape is the flattest.

Yes. The field is stronger where the shape is more pointed

What is the electric field inside a conductor with 2nC of net negative charge? Zero Infinite The field inside depends on the shape of the conductor The field inside depends on the type of conductor

Zero

Materials in which charges move easily are known as Dipoles Conductors Insulators Coulombs

conductors

The force between an electron and proton Is repulsive Is attractive Is weaker the closer they are to each other Changes direction depending on the distance between them

is attractive

When do electric field lines cross? If 2 positive charges are close together If a positive charge is close to a negative charge Always Never

never

Video 1: What is the sign of the charge on the sticky side of the tape after he sticks 2 pieces of tape together and then pulls them apart? Positive There is no charge on the tape. Negative It depends on what type of tape is used

positive

The electric potential energy of a charge q in terms of the electric potential, V, of the space around it is V/q q/V qV V+qE

qV

Neutral objects have zero net electric charge because There is nothing with electric charge in them The charges in them are moving too fast to measure There are equal amounts of positive and negative charge All charge has been removed.

there are equal amounts of positive and negative charge

How is the potential difference, ΔV, in a capacitor related to the charge, Q, and the capacitance, C? ΔV = QC ΔV = C/Q ΔV = Q/C ΔV = QC^2

ΔV = Q/C