Electric Potential
Q. A capacitor has a capacitance of 10 μF and is charged to a potential of 50 V. What is the energy stored in the capacitor?
A.
0.025 J
B.
0.05 J
C.
0.1 J
D.
0.5 J
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Solution
Energy stored U = 1/2 * C * V² = 1/2 * 10 × 10^-6 F * (50 V)² = 0.0125 J.
Correct Answer: A — 0.025 J
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Q. A capacitor has a capacitance of 5 μF and is charged to a potential of 12 V. What is the energy stored in the capacitor?
A.
0.36 mJ
B.
0.72 mJ
C.
0.12 mJ
D.
0.24 mJ
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Solution
Energy U = 1/2 * C * V² = 1/2 * 5 × 10^-6 F * (12 V)² = 0.36 mJ.
Correct Answer: B — 0.72 mJ
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Q. A capacitor is charged to a potential difference of 12 V. If the capacitance is 4 µF, what is the charge stored in the capacitor?
A.
12 µC
B.
24 µC
C.
48 µC
D.
36 µC
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Solution
Charge Q is given by Q = CV. Here, Q = 4 µF * 12 V = 48 µC.
Correct Answer: B — 24 µC
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Q. A capacitor is charged to a potential difference of V. What is the energy stored in the capacitor?
A.
1/2 CV²
B.
CV
C.
V²/C
D.
1/2 QV
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Solution
The energy (U) stored in a capacitor is given by U = 1/2 CV², where C is the capacitance and V is the potential difference.
Correct Answer: A — 1/2 CV²
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Q. A capacitor is charged to a potential of 12 V. If the capacitance is 3 µF, what is the energy stored in the capacitor?
A.
0.18 mJ
B.
0.36 mJ
C.
0.54 mJ
D.
0.72 mJ
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Solution
Energy stored in a capacitor is given by U = 1/2 CV² = 1/2 * 3 x 10^-6 F * (12 V)² = 0.36 mJ.
Correct Answer: B — 0.36 mJ
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Q. A capacitor is charged to a potential of 12 V. If the capacitance is 4 µF, what is the energy stored in the capacitor?
A.
0.24 mJ
B.
0.48 mJ
C.
0.12 mJ
D.
0.36 mJ
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Solution
Energy stored U = 1/2 CV² = 1/2 * 4 x 10^-6 F * (12 V)² = 0.24 mJ.
Correct Answer: B — 0.48 mJ
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Q. A capacitor is charged to a potential of V. If the charge on the capacitor is doubled, what will be the new potential?
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Solution
The potential V across a capacitor is directly proportional to the charge. If the charge is doubled, the potential also doubles.
Correct Answer: B — 2V
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Q. A charge of -2 μC is placed in an electric field of 1000 N/C. What is the potential energy of the charge? (2000)
A.
-2000 J
B.
2000 J
C.
0 J
D.
-1000 J
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Solution
Potential energy U = q * V = -2 × 10^-6 C * 1000 N/C = -0.002 J.
Correct Answer: A — -2000 J
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Q. A charge of -4 μC is placed in an electric field of 200 N/C. What is the potential energy of the charge?
A.
-800 μJ
B.
800 μJ
C.
400 μJ
D.
0 μJ
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Solution
Potential energy U = q * V = -4 × 10^-6 C * 200 N/C = -800 μJ.
Correct Answer: A — -800 μJ
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Q. A charge of 4 μC is placed at the origin. What is the electric potential at a point 3 m away?
A.
3000 V
B.
1200 V
C.
4000 V
D.
None of the above
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Solution
V = k * q / r = (9 × 10^9 N m²/C²) * (4 × 10^-6 C) / (3 m) = 1200 V.
Correct Answer: B — 1200 V
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Q. A charge of 4 μC is placed at the origin. What is the electric potential at a point (3, 4) m?
A.
300 V
B.
200 V
C.
100 V
D.
0 V
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Solution
Distance r = √(3² + 4²) = 5 m. V = k * q / r = (9 × 10^9) * (4 × 10^-6) / 5 = 720 V.
Correct Answer: B — 200 V
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Q. A charge of 5 μC is placed in an electric field of 2000 N/C. What is the electric potential energy of the charge?
A.
10 mJ
B.
1 mJ
C.
0.5 mJ
D.
2 mJ
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Solution
Electric potential energy (U) = Charge × Electric Field = 5 μC × 2000 N/C = 10 mJ.
Correct Answer: A — 10 mJ
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Q. A charge of 5 μC is placed in an electric field of 2000 N/C. What is the potential energy of the charge?
A.
10 mJ
B.
1 mJ
C.
0.5 mJ
D.
2 mJ
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Solution
Potential energy (U) = Charge × Electric Field × Distance. Assuming distance = 1 m, U = 5 μC × 2000 N/C = 10 mJ.
Correct Answer: A — 10 mJ
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Q. A charged capacitor has a potential difference of 12 V across its plates. If the capacitance is 4 µF, what is the charge stored in the capacitor?
A.
48 µC
B.
12 µC
C.
3 µC
D.
24 µC
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Solution
Charge Q = C × V = 4 µF × 12 V = 48 µC.
Correct Answer: A — 48 µC
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Q. A charged particle moves from a point of higher electric potential to a point of lower electric potential. What happens to its kinetic energy?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Cannot be determined
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Solution
As the charged particle moves to a lower potential, it loses potential energy, which is converted into kinetic energy, thus increasing its kinetic energy.
Correct Answer: A — Increases
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Q. A charged particle moves from a region of high potential to low potential. What happens to its kinetic energy?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
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Solution
As the charged particle moves from high potential to low potential, it loses potential energy, which is converted into kinetic energy, thus its kinetic energy increases.
Correct Answer: A — It increases
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Q. A charged sphere has a radius R and a total charge Q. What is the electric potential at a point outside the sphere at a distance r from the center (r > R)?
A.
kQ/R
B.
kQ/r
C.
kQ/(R+r)
D.
0
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Solution
For a charged sphere, the electric potential outside the sphere behaves as if all the charge were concentrated at the center, so V = kQ/r.
Correct Answer: B — kQ/r
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Q. A parallel plate capacitor has a potential difference of V across its plates. What is the electric field between the plates?
A.
V/d
B.
d/V
C.
V²/d
D.
d²/V
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Solution
The electric field E between the plates of a parallel plate capacitor is given by E = V/d, where d is the separation between the plates.
Correct Answer: A — V/d
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Q. A point charge of +5 µC is placed at the origin. What is the electric potential at a point 2 m away from the charge?
A.
1125 V
B.
450 V
C.
225 V
D.
0 V
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Solution
The electric potential V at a distance r from a point charge Q is given by V = kQ/r. Here, V = (9 x 10^9 Nm²/C²)(5 x 10^-6 C)/(2 m) = 1125 V.
Correct Answer: A — 1125 V
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Q. A spherical conductor has a charge Q. What is the electric potential inside the conductor?
A.
0
B.
Q/(4πε₀r)
C.
Q/(4πε₀R)
D.
Constant throughout
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Solution
The electric potential inside a charged spherical conductor is constant and equal to the potential on its surface, which is Q/(4πε₀R).
Correct Answer: D — Constant throughout
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Q. A spherical conductor has a radius R and carries a charge Q. What is the electric potential on its surface?
A.
kQ/R
B.
kQ/2R
C.
0
D.
kQ/R²
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Solution
The electric potential V on the surface of a charged spherical conductor is given by V = kQ/R.
Correct Answer: A — kQ/R
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Q. If the electric potential at a point is 0 V, what can be said about the electric field at that point?
A.
It is zero
B.
It is positive
C.
It is negative
D.
It cannot be determined
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Solution
The electric field is the negative gradient of the electric potential. If the potential is constant (0 V), the electric field is zero.
Correct Answer: A — It is zero
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Q. If the electric potential at a point is 10 V and the charge at that point is 2 C, what is the electric potential energy?
A.
5 J
B.
10 J
C.
20 J
D.
40 J
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Solution
Electric potential energy U is given by U = VQ. Here, U = 10 V * 2 C = 20 J.
Correct Answer: C — 20 J
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Q. If the electric potential at a point is 10 V and the electric field is uniform, what is the work done in moving a charge of 2 C from that point to a point where the potential is 0 V?
A.
20 J
B.
10 J
C.
5 J
D.
0 J
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Solution
Work done W = q(V1 - V2) = 2 C (10 V - 0 V) = 20 J.
Correct Answer: A — 20 J
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Q. If the electric potential at a point is 10 V, what is the work done in bringing a charge of 2 C from infinity to that point?
A.
20 J
B.
10 J
C.
5 J
D.
40 J
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Solution
Work done = Charge × Potential = 2 C × 10 V = 20 J.
Correct Answer: A — 20 J
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Q. If the electric potential at a point is 100 V and the electric field is 50 N/C, what is the distance from the charge?
A.
2 m
B.
1 m
C.
0.5 m
D.
4 m
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Solution
Distance d = V / E = 100 V / 50 N/C = 2 m.
Correct Answer: A — 2 m
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Q. If the electric potential at a point is 100 V, what is the work done in moving a charge of 2 C from infinity to that point?
A.
200 J
B.
100 J
C.
50 J
D.
0 J
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Solution
Work done W = q * V = 2 C * 100 V = 200 J.
Correct Answer: A — 200 J
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Q. If the electric potential at a point is 150 V and the electric field is uniform, what is the potential difference over a distance of 3 m?
A.
50 V
B.
150 V
C.
100 V
D.
200 V
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Solution
Potential difference ΔV = E * d = (150 V / 3 m) * 3 m = 150 V.
Correct Answer: A — 50 V
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Q. If the electric potential at a point is 200 V and a charge of -1 C is placed at that point, what is the potential energy?
A.
-200 J
B.
200 J
C.
0 J
D.
100 J
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Solution
Potential energy U = q * V = -1 C * 200 V = -200 J.
Correct Answer: A — -200 J
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Q. If the electric potential at a point is 200 V and the electric field is uniform, what is the work done in moving a charge of 0.5 C to a point where the potential is 100 V?
A.
50 J
B.
100 J
C.
200 J
D.
0 J
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Solution
Work done W = q * (V1 - V2) = 0.5 C * (200 V - 100 V) = 50 J.
Correct Answer: B — 100 J
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