Electric Fields and Gauss's Law Concepts

Inside a uniformly charged conducting shell, the electric field is

• Zero everywhere inside

• Constant everywhere inside

• Inversely proportional to r² inside

• Directed radially outward, increasing with r

The main reason Gauss’s law is powerful for an infinite line of charge is

• The line produces no electric field

• The symmetry makes the field constant on the Gaussian surface

• The field strength does not depend on distance

• Charges cancel out everywhere

If you double the radius of a spherical Gaussian surface while keeping the enclosed charge fixed, the electric flux through the surface

• Doubles

• Quadruples

• Stays the same

• Goes to zero

A proton moves in the direction of a uniform electric field. What happens?

• Potential energy increases, kinetic decreases

• Potential energy decreases, kinetic increases

• Both potential and kinetic increase

• Both potential and kinetic decrease

Two point charges are separated by a distance r. If you double the separation, the potential energy

• Doubles

• Halves

• Becomes zero

• Remains constant

Why is the electric field always perpendicular to equipotential surfaces?

• Otherwise charges would stop moving

• Otherwise the surface would have thickness

• Otherwise there would be work done along the surface

• Otherwise the charge density would change

Inserting a dielectric between capacitor plates increases capacitance because

• It increases the distance between plates

• It cancels the electric field inside the dielectric

• It reduces the effective field, allowing more charge storage

• It increases the voltage across the plates

Doubling the plate area of a parallel-plate capacitor (with same separation) will

• Double the electric field, double the capacitance

• Leave the electric field the same, double the capacitance

• Halve the electric field, leave capacitance unchanged

• Double both the field and stored energy

A dipole placed in a uniform electric field experiences

• Net force but no torque

• Torque but no net force

• Both torque and net force

• Neither torque nor net force

Why does the field of a dipole fall off faster (∝ 1/r³) than that of a point charge (∝ 1/r²)?

• Dipole fields cancel more at long range

• Dipoles have less charge

• Gauss’s law doesn’t apply to dipoles

• The dipole field is always weaker