Charge & Force
Electric Fields
V and U
Capacitors
125
When somebody is shocked after they touch a positively-charged ball, what happened between their hand and the ball?
Electrons jumped from the person's hand to the ball
125
By convention, electric field lines point away from _____________ charged objects and towards _____________ charged objects.
positively; negatively
125
DOUBLE POINTS
What are the SI base units for Voltage (include kg)?
kg⋅m2/s2⋅C
or
kg⋅m2/s3⋅A
125
The insulating material placed between the plates of a capacitor is known as the ______________.
Dielectric
150
Electric charge is said to be quantized, meaning every charged object is a multiple of how many Coulombs?
1.6x10-19 C
150
What are the SI base units of Electric Field (using kg)?
kg*m/C*s2
or
kg*m/A*s3
150
A point charge of -3Q is moved from an electric potential of -5 V to +10 V. What is the change in electric potential energy of this charge?
- 45 J
150
A Voltage V is applied to a capacitor which stores charge Q on the plates. If the area and separation of the capacitor plates are both doubled, and the voltage is halved, what is the new charge on the plates?
Q/2
(use Q = CV and C ∝ A/d)
200
What are the units for Coulomb's constant (k)?
N*m2/C2
200
The radius of sphere X is greater than that of sphere Y, and the magnitudes of the electric fields just outside their surfaces are the same. How does the charge on sphere X compare with that on sphere Y ?
Sphere X's charge is greater
200
In a V vs. distance graph, sketch the electric potential from 0 to 2r for a uniformly charged spherical conductor of radius r.
The graph should show a constant, nonzero voltage from 0 to r, then a V = 1/r shaped curve from r to 2r.
200
DOUBLE POINTS
What is the equation for the equivalent (total) capacitance of a circuit containing 3 capacitors in series?
1/Ceq = 1/C1+1/C2+1/C3
300
Connecting a charged system to a much larger, neutrally charged system is known as _____________.
grounding (a.k.a. earthing)
300
A hollow, metal box is placed between two parallel charged plates. Draw the electric field between the plates.
(there should be no electric field lines inside and including the metal box's walls)
300
Charge +Q is located at the center of the hollow metal sphere shown in cross section above. The net charge on the sphere is zero. If the potential of the inner surface is V, is the potential of the outer surface greater than, less than, or equal to V?
Equal to V
300
What are the SI base units for Capacitance (use kg)?
s2*C2/kg*m2
or
A2*s4/kg*m2
325
When a material is placed in an electric field, the ease with which it becomes polarized is known as __________________________.
electric permittivity (ε)
325
Explain why an electric field inside a solid (or hollow) conducting sphere must always be zero, in terms of any charges involved.
When an electric field is applied to a conductor, the charges will move accordingly (negatives move against the E lines) until they balance the electric field.
325
Compare the magnitude of the electric field at points A and B AND give the direction of the electric field at these points.
EA>EB
EB points to the right, EA points to the left (E lines go from greater, positive V to lower V)
325
One way to measure the ability of the insulator to store electric energy is to measure its polarization in the presence of an electric field, known as electric permittivity. Dividing this permittivity by Vacuum Permittivity gives us the ____________________ of the insulator.
dielectric constant