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RIO SALADO PHYSICS 112 FINAL ACTUAL
EXAM PREP 2026 ( 2 CURRENTLY TESTING
VERSIONS ) ALL QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
A GRADED WITH EXPERT FEEDBACK |NEW
AND REVISED
1. Two identical point charges +Q are separated by distance d. Electric
potential at midpoint is:
A. 0
B. Negative
C. Positive
D. Undefined
Rationale: Potentials from each positive charge add, giving a positive
sum at the midpoint.
2. Coulomb’s law gives force between two charges; force magnitude ∝:
A. 1/r
B. 1/r²
C. r²
D. r
Rationale: Coulomb’s law states (F=k\frac{q_1q_2}{r^2}).
3. Gauss’s law is most useful for finding E when charge distribution has:
A. Arbitrary shape
B. High symmetry (spherical, cylindrical, planar)
C. Time dependence only
D. No symmetry
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Rationale: Symmetry lets you pull E out of surface integrals to solve
easily.
4. Electric field inside a hollow conducting shell in electrostatic
equilibrium is:
A. Nonzero if external charges present
B. Zero
C. Uniform nonzero
D. Infinite at center
Rationale: Inside a conductor in equilibrium, charges reside on
surfaces so E = 0 inside conductor material and hollow interior
(absent internal charges).
5. Electric potential difference between two points equals:
A. Negative line integral of E from one to the other
B. Sum of fields times area
C. Negative of the work per unit charge done by the field
D. Product of charges
Rationale: (\Delta V = -\int \mathbf{E}\cdot d\mathbf{\ell}) equals
negative work/charge by the field.
6. A positive test charge released from rest in an electric field will move:
A. From low potential to high potential
B. Toward lower potential (decreasing V)
C. Randomly
D. Toward higher potential if field nonuniform
Rationale: Positive charges lose potential energy moving toward lower
potential (field does positive work).
7. Capacitance of parallel-plate capacitor ∝:
A. Plate separation d
B. Plate area A
C. Voltage squared
D. Inverse dielectric constant
Rationale: (C=\varepsilon_0\varepsilon_r A/d) so C ∝ A.
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8. Adding a dielectric (κ>1) between plates of an isolated charged
capacitor (isolated Q fixed) causes:
A. Voltage increase
B. Voltage decrease
C. No change in voltage
D. Charge to change
Rationale: With Q fixed, C increases so V=Q/C decreases.
9. Energy stored in capacitor (U=\tfrac{1}{2}CV^2); doubling V (C
fixed) changes U by:
A. Doubled
B. Quadrupled
C. Halved
D. Unchanged
Rationale: U ∝ V² so doubling V gives 4× energy.
10. Two capacitors in series C1 and C2 have equivalent Ceq:
A. C1 + C2
B. C1 C2
C. (1/C1 + 1/C2)^{-1}
D. |C1 − C2|
Rationale: Series capacitors add reciprocally.
11. Surface charge density σ on conductor produces field just outside:
A. σ/(2ε0)
B. σ/ε0 (normal to surface)
C. Zero
D. σ²/ε0
Rationale: Boundary condition gives (E_{out} = \sigma/\varepsilon_0)
normal to surface.
12. Potential is defined up to an arbitrary additive constant because only
potential differences are physically measurable; true or false?
A. False
B. True
C. Only for conductors
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D. Only in vacuum
Rationale: Only differences matter for work; absolute reference
arbitrary.
13. For point charge Q at origin, V(r) ∝:
A. r²
B. 1/r
C. ln r
D. r
Rationale: Potential of point charge (V=kQ/r).
14. If E = 0 everywhere in region, the potential in that region is:
A. Zero
B. Increasing linearly
C. Spatially constant (may be nonzero constant)
D. Undefined
Rationale: E = −∇V, so zero field implies V constant (not necessarily
zero).
15. A charge +q brought slowly to a point where potential V is positive
gains potential energy ΔU =:
A. −qV
B. +qV
C. q/V
D. Independent of q
Rationale: ΔU = q ΔV with ΔV positive gives positive ΔU.
16. In conductors, excess charge resides:
A. At interior points
B. Only on the outer surface
C. On imaginary interior lines
D. Uniformly in volume always
Rationale: Free charges move until they reside on outer surfaces at
equilibrium.
RIO SALADO PHYSICS 112 FINAL ACTUAL
EXAM PREP 2026 ( 2 CURRENTLY TESTING
VERSIONS ) ALL QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
A GRADED WITH EXPERT FEEDBACK |NEW
AND REVISED
1. Two identical point charges +Q are separated by distance d. Electric
potential at midpoint is:
A. 0
B. Negative
C. Positive
D. Undefined
Rationale: Potentials from each positive charge add, giving a positive
sum at the midpoint.
2. Coulomb’s law gives force between two charges; force magnitude ∝:
A. 1/r
B. 1/r²
C. r²
D. r
Rationale: Coulomb’s law states (F=k\frac{q_1q_2}{r^2}).
3. Gauss’s law is most useful for finding E when charge distribution has:
A. Arbitrary shape
B. High symmetry (spherical, cylindrical, planar)
C. Time dependence only
D. No symmetry
,2|Page
Rationale: Symmetry lets you pull E out of surface integrals to solve
easily.
4. Electric field inside a hollow conducting shell in electrostatic
equilibrium is:
A. Nonzero if external charges present
B. Zero
C. Uniform nonzero
D. Infinite at center
Rationale: Inside a conductor in equilibrium, charges reside on
surfaces so E = 0 inside conductor material and hollow interior
(absent internal charges).
5. Electric potential difference between two points equals:
A. Negative line integral of E from one to the other
B. Sum of fields times area
C. Negative of the work per unit charge done by the field
D. Product of charges
Rationale: (\Delta V = -\int \mathbf{E}\cdot d\mathbf{\ell}) equals
negative work/charge by the field.
6. A positive test charge released from rest in an electric field will move:
A. From low potential to high potential
B. Toward lower potential (decreasing V)
C. Randomly
D. Toward higher potential if field nonuniform
Rationale: Positive charges lose potential energy moving toward lower
potential (field does positive work).
7. Capacitance of parallel-plate capacitor ∝:
A. Plate separation d
B. Plate area A
C. Voltage squared
D. Inverse dielectric constant
Rationale: (C=\varepsilon_0\varepsilon_r A/d) so C ∝ A.
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8. Adding a dielectric (κ>1) between plates of an isolated charged
capacitor (isolated Q fixed) causes:
A. Voltage increase
B. Voltage decrease
C. No change in voltage
D. Charge to change
Rationale: With Q fixed, C increases so V=Q/C decreases.
9. Energy stored in capacitor (U=\tfrac{1}{2}CV^2); doubling V (C
fixed) changes U by:
A. Doubled
B. Quadrupled
C. Halved
D. Unchanged
Rationale: U ∝ V² so doubling V gives 4× energy.
10. Two capacitors in series C1 and C2 have equivalent Ceq:
A. C1 + C2
B. C1 C2
C. (1/C1 + 1/C2)^{-1}
D. |C1 − C2|
Rationale: Series capacitors add reciprocally.
11. Surface charge density σ on conductor produces field just outside:
A. σ/(2ε0)
B. σ/ε0 (normal to surface)
C. Zero
D. σ²/ε0
Rationale: Boundary condition gives (E_{out} = \sigma/\varepsilon_0)
normal to surface.
12. Potential is defined up to an arbitrary additive constant because only
potential differences are physically measurable; true or false?
A. False
B. True
C. Only for conductors
, 4|Page
D. Only in vacuum
Rationale: Only differences matter for work; absolute reference
arbitrary.
13. For point charge Q at origin, V(r) ∝:
A. r²
B. 1/r
C. ln r
D. r
Rationale: Potential of point charge (V=kQ/r).
14. If E = 0 everywhere in region, the potential in that region is:
A. Zero
B. Increasing linearly
C. Spatially constant (may be nonzero constant)
D. Undefined
Rationale: E = −∇V, so zero field implies V constant (not necessarily
zero).
15. A charge +q brought slowly to a point where potential V is positive
gains potential energy ΔU =:
A. −qV
B. +qV
C. q/V
D. Independent of q
Rationale: ΔU = q ΔV with ΔV positive gives positive ΔU.
16. In conductors, excess charge resides:
A. At interior points
B. Only on the outer surface
C. On imaginary interior lines
D. Uniformly in volume always
Rationale: Free charges move until they reside on outer surfaces at
equilibrium.
