Physics 262 Final Exam

Which is true about the magnetic field lines of a solenoid?

Internally, they are closely spaced with a uniform spacing. Externally, they are more widely spaced with a nonuniform spacing.

Which is true about the potential energy stored in an inductor?

It depends on the current.

Which is true about the self-induced emf of an inductor?

It depends on the rate at which the current through it is changing.

When an initially uncharged capacitor is charged in an RC circuit, what happens to the net potential difference around the full circuit loop?

It does not change.

For most materials, how does an increase in temperature affect the resistivity?

It increases the resistivity.

Which is true about the inductance of an inductor?

It is equal to the ratio of the magnetic flux linkage to the current.

Which describes the orientation of an equipotential surface?

It is perpendicular to the electric field vectors.

Which is true about the electric potential along the central axis of a positively charged disk?

It is positive for every point.

In the Biot-Savart law, which describes angle θ?

It is the angle between the direction of the current in a current-length element and a vector directed from that element toward the point of measurement.

Which gives the amount of charge on a certain length of a rod that is uniformly charged?

It is the product of the length and the linear charge density.

In the demonstration where a loop is pulled out of a magnetic field, which gives the power of your pull?

It is the product of your force and the speed at which the loop moves.

Which is the energy density of a magnetic field?

It is the ratio of the total potential energy to the volume.

Which describes Gauss' law?

It relates the net flux through a closed surface to the net charge enclosed by the surface.

When an electron circles in a uniform circular motion, which describes its kinetic energy?

It remains the same.

If we were to gradually charge a capacitor by transferring charge from one plate to the other, which describes the action of the electric field between the plates?

It resists our transfer of charge.

Which is true if we bring together a negatively charged particle and a positively charged particle?

Our work is negative.

How is the charge stored on a capacitor related to the capacitance of the capacitor and the potential difference across the capacitor?

The charge equals the product of the capacitance and the potential difference.

An electric dipole is in a uniform electric field. For which orientation is the potential energy of the dipole least?

The dipole moment is in the direction of the electric field.

In evaluating the integral in Gauss' law for a spherical surface centered on a positively charged particle, which describes the dot product of the electric field and a differential area vector?

The dot product is positive because the vectors are in the same direction.

Which is true? The drift speeds are much more than the random-motion speeds. The drift speeds are much less than the random-motion speeds. The drift speeds are comparable to the random-motion speeds.

The drift speeds are much less than the random-motion speeds.

A charged particle moves through uniform electric and magnetic fields. In which case is there the possibility that the electric force and magnetic force cancel?

The electric field and the magnetic field are perpendicular.

In a cyclotron, where is the electric field and where is the magnetic field?

The electric field is in the gap; the magnetic field is throughout the apparatus.

Which describes the electric field near a sphere with uniform negative charge?

The electric field lines extend radially toward the sphere

A battery is connected to a wire. If we think of current in the wire as being the motion of conduction electrons, which describes that motion?

The electrons move in the direction opposite the electric field along the wire.

Which is true about the equivalent of resistors in parallel?

The equivalent resistance is less than the smallest value of the individual resistances.

If we place a nonpolar molecule in an electric field, which is true?

The field induces a dipole moment, with the positive end of the molecule in the direction of the field vector.

Which describes the magnetic field along the central axis of a current loop?

The field is directed along the axis and away from the loop on one side and toward the loop on the other side.

How do we find an electric field from a plot of the electric potential?

The field is the negative of the slope of the plot of the electric potential.

In a uniform field, how is the magnitude of the electric field related to the change in potential between two equipotential surfaces?

The field magnitude is the ratio of the potential change to the distance between the two surfaces.

Which describes the flux of an electric field that pierces inward through a section on a closed surface?

The flux is negative.

Which gives the force on a charged particle placed in an electric field?

The force is the product of the charge and the electric field.

A positively charged particle is placed inside (in the hollow of) a shell of uniform negative charge. Which describes the force on the particle due to the shell?

The force is zero.

We set up two parallel currents in the same direction. Which describes the magnetic force on each wire due to the other wire?

The force on each current is perpendicular to the current and toward the other current.

In the two-coil setup in this section, which is true?

The induced emf in each coil depends on the rate that the current is changing in the other coil.

Which is true about a solenoid?

The internal magnetic field is approximately uniform. The external magnetic field is weak.

Which is correct about a voltmeter?

The internal resistance must be much greater than the other resistances in the circuit.

How is the linear charge density of a uniformly charged ring related to total amount of charge?

The linear charge density is the ratio of the total charge to the circumference.

A current loop is in a uniform magnetic field. Which describes the rotation of the loop?

The loop tends to rotate so that the normal vector is in the direction of the magnetic field vector.

Which describes the net force on a magnetic dipole in a uniform magnetic field?

The net force vector is zero.

A junction point in the wire of a circuit has inward current of 5.0 A. Which is true?

The outward current must be 5.0 A.

Which of the following describes the triple point of water?

The particular value of temperature and the particular value of pressure at which liquid water, solid ice, and water vapor can coexist.

In a Hall effect experiment, how is the potential difference across the width related to the electric field magnitude?

The potential difference is the product of the field magnitude and the width.

Which describes the vector calculations of the potential energy and torque for an electric dipole in an electric field?

The potential energy involves a dot product; the torque involves a cross product.

We bring a proton near a positively charged flat metal sheet. Which describes the surface charge density at the region on the sheet that is closest to the proton?

The presence of the proton decreases the magnitude of the surface charge density.

When an RL circuit is connected to a battery, what happens to the potential difference across the resistor and the emf across the inductor?

The resistor potential increases and the inductor emf decreases.

We place a closed Gaussian cylinder around a rod with uniform negative charge, coaxial with the rod. Then we pick a small region on the curved surface of the cylinder. Which describes the electric field there and the area vector of the small region?

The vectors are in opposite directions.

A Gaussian sphere is inside a ball of uniform positive charge, concentric with the ball. Which describes the electric field vectors along the surface of the Gaussian sphere?

The vectors are radially outward.

When conduction electrons pass through a device with resistance, which describes their energy?

Their potential energy decreases.

Which describes the electric field lines near a positively charged particle?

They are more crowded near the particle than farther out.

Which describes the electric field lines outside a flat plastic sheet with uniform negative charge?

They extend directly toward the sheet.

What is the direction of the electric field lines set up by a negatively charged particle?

They extend radially toward the particle

Which is true about resistors in series?

They have the same current.

Which is true about capacitors in parallel?

They have the same potential difference.

Pick a point on the dipole axis of an electric dipole, outside the dipole, on the negative side of the dipole. What is the direction of the electric field there?

along the axis, toward the dipole

On which does the capacitance of a parallel-plate capacitor depend?

area of the plates

If a negatively charged plastic rod is brought near one end of a neutral copper rod, what happens to that near end?

becomes positively charged

When charged particles move through a conductor such as copper wire, what moves?

conduction electrons

If a material has a high R-value, how well does it conduct energy as heat?

conducts poorly

If a positively charged particle is released in an electric field, in what direction does it move?

in the direction of the electric field vector at its location

If a positive test charge is placed in an electric field, what is the direction of the force on the test charge?

in the direction of the vector field

Initially, a single capacitance C1 is wired to a battery. Then capacitance C2 is added in parallel. (c) Is the equivalent capacitance C12 of C1 and C2 more than, less than, or equal to C1?

more than

Initially, a single capacitance C1 is wired to a battery. Then capacitance C2 is added in parallel. (d) Is the charge stored on C1 and C2 together more than, less than, or equal to the charge stored previously on C1?

more than

If a thermodynamic process of a gas gives a leftward transition on a p-V diagram, which of these describes the work done by the gas?

negative

When a dielectric slab fills the gap in a parallel-plate capacitor, what is the sign of the induced charge next to the positively charged plate?

negative

When energy is transferred from a system as heat, what is the sign given to the transfer?

negative

If the circular conductor in the figure undergoes thermal expansion while it is in a uniform magnetic field, a current is induced clockwise around it. Is the magnetic field directed into or out of the page?

out of

Initially, a single capacitance C1 is wired to a battery. Then capacitance C2 is added in parallel. (a) Is the potential difference across C1 now more than, less than, or the same as previously?

same as

Initially, a single capacitance C1 is wired to a battery. Then capacitance C2 is added in parallel. (b) Is the charge q1 on C1 now more than, less than, or the same as previously?

same as

Which describes a surface charge density?

the charge per unit area

What do we calculate if we integrate length element ds around a full circle?

the circumference of the circle

When we found the electric field of a charged ring at a point on the ring's central axis, which did we sum?

the field components parallel to the central axis

What is indicated by a region with field lines drawn close together?

the magnitude of the field is large in the region

What is the atomic number of an atom?

the number of protons in an atom

If a dielectric is inserted into a capacitor while the capacitor is connected to a battery, what remains constant?

the potential difference between the plates

Which gives the magnitude of an electric dipole moment?

the product of the charge and the distance separating the particles

When the current density in a wire is uniform, which gives the amount of current through a cross section of the wire?

the product of the cross-sectional area and the current density

When we embed a Gaussian cylinder in a flat metal surface with uniform charge, perpendicular to the surface, what gives the amount of charge enclosed by the cylinder?

the product of the surface charge density and the cross-sectional area of the cylinder

When we stick a Gaussian cylinder through a flat plastic sheet with uniform charge, perpendicular to the sheet, what gives the amount of charge enclosed by the cylinder?

the product of the surface charge density and the cross-sectional area of the cylinder

In the demonstration where a magnet is brought near a loop, what determines the induced current?

the rate at which the number of magnetic field lines intercepted by the loop changes

For a wire with a uniform electric field along its length, which gives the magnitude of the field?

the ratio of the potential difference (end to end) to the length

No doubt you have rubbed your feet across a carpet and then touched a door knob and received a shock. Which of the following statements are true? I Rubbing your feet across the carpet results in your body having a non-zero net electric charge. II Rubbing your feet across the carpet results in an exchange of electric charge between you and the carpet. III As your hand nears the door knob it induces an opposite charge on the door knob.

I, II, and III

Which is true about moving through an emf device that is connected to a resistor?

If you move in the direction of the emf arrow, the potential increases.

Which is true? A changing magnetic field produces a constant perpendicular magnetic field. A changing magnetic field produces a changing perpendicular magnetic field. A changing magnetic field produces a constant parallel magnetic field. A changing magnetic field produces a changing parallel magnetic field. A changing magnetic field produces an electric field.

A changing magnetic field produces an electric field.

Which temperature scale has the freezing point of water at zero?

Celsius

Which is true about the spacing of the streamlines in a wire?

Close spacing represents greater current densities.

Which is correct about the charge movement when a battery is connected to copper wire?

Electrons leave the negative battery terminal and electrons enter the positive terminal.

In finding the net electric potential due to several charged particles, which is true?

We add the contributions as scalars, complete with the algebraic signs.

If we move a positively charged particle through an electric field, in which situation do we decrease the electric potential energy of the particle?

We move the particle in the direction of the electric field.

Which describes the procedure for finding the magnetic field on the central axis of a current loop due to the elements on the loop?

We sum the field components that are parallel to the central axis.

When is the electric flux on a section of a closed surface positive?

When the electric field is in the direction of the section's area vector.

A wire with current lies in a uniform magnetic field. In which situation is the magnetic force on the wire zero?

When the length vector is in the direction of the magnetic field vector.

A charged particle moves through a magnetic field. In which situation is the magnetic force zero?

When the particle moves in the direction of the magnetic field vector.

Which of these particles has the smallest amount of negative charge?

electron

Which arrangement is called an electric dipole?

two particles with the same magnitude of charge but with opposite signs

How is the coefficient of volume expansion β related to the coefficient of linear expansion α?

β is equal to 3α.