physics : class12 Potential of Multiple Point Charges : Superposition Principle : Electrostatics MCQ Questions and Answers
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Potential of Multiple Point Charges
MCQ questions and answers.
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MCQ Questions
1. The electric potential at a point due to several point charges is calculated by:
A.
Adding the electric potentials due to each charge algebraically
B.
Adding the magnitudes of electric fields due to each charge
C.
Multiplying the individual electric potentials
D.
Adding only the potentials due to positive charges
Correct Answer:
Adding the electric potentials due to each charge algebraically
Explanation:
Electric potential is a scalar quantity, so the total potential is the algebraic sum of the potentials produced by all the point charges.
2. The electric potential at a point due to a point charge q at distance r is given by:
A.
V = kq/r
B.
V = kq/r²
C.
V = kr/q
D.
V = q/(kr)
Correct Answer:
V = kq/r
Explanation:
The potential due to a point charge is V = kq/r, where k is Coulomb's constant, q is the charge, and r is the distance from the charge.
3. Two point charges +q and +q are placed at equal distances from a point P. If the potential due to each charge at P is V, the total potential at P is:
A.
0
B.
V
C.
2V
D.
V/2
Correct Answer:
2V
Explanation:
Both charges produce positive potential V at point P. Since potential is a scalar, the potentials add algebraically to give 2V.
4. Two equal and opposite point charges, +q and -q, are placed at equal distances from point P. What is the net potential at P?
A.
2kq/r
B.
kq/r
C.
0
D.
kq/r²
Correct Answer:
0
Explanation:
The positive charge produces potential kq/r and the negative charge produces -kq/r at equal distance r. Their algebraic sum is zero.
5. A charge of +2 microcoulombs is 1 metre from a point P. Taking k = 9 × 10^9 N m²/C², the potential at P is:
A.
9 × 10^3 V
B.
18 × 10^3 V
C.
4.5 × 10^3 V
D.
18 × 10^6 V
Correct Answer:
18 × 10^3 V
Explanation:
Using V = kq/r, V = (9 × 10^9)(2 × 10^-6)/1 = 18 × 10^3 V.
6. Two point charges of +3 microcoulombs and +2 microcoulombs are each 1 metre from point P. Taking k = 9 × 10^9 N m²/C², the potential at P is:
A.
9 × 10^3 V
B.
18 × 10^3 V
C.
45 × 10^3 V
D.
5 × 10^3 V
Correct Answer:
45 × 10^3 V
Explanation:
The total potential is k(q1 + q2)/r = (9 × 10^9)(5 × 10^-6)/1 = 45 × 10^3 V.
7. A point P is 2 m from a charge of +4 microcoulombs. Taking k = 9 × 10^9 N m²/C², the potential at P is:
A.
9 × 10^3 V
B.
18 × 10^3 V
C.
36 × 10^3 V
D.
72 × 10^3 V
Correct Answer:
18 × 10^3 V
Explanation:
Using V = kq/r, V = (9 × 10^9)(4 × 10^-6)/2 = 18 × 10^3 V.
8. If a point charge is moved farther from an observation point, its contribution to the electric potential at that point:
A.
Increases
B.
Decreases
C.
Remains unchanged
D.
Becomes equal to the charge itself
Correct Answer:
Decreases
Explanation:
The potential due to a point charge is V = kq/r. Increasing the distance r decreases the magnitude of its potential contribution.
9. Three point charges produce potentials +5 V, -2 V, and +3 V at point P. The net potential at P is:
A.
0 V
B.
6 V
C.
10 V
D.
-6 V
Correct Answer:
6 V
Explanation:
The total potential is the algebraic sum: +5 V - 2 V + 3 V = +6 V.
10. At a point P, a charge +q is at distance r and a charge +2q is at distance 2r. If the potential due to +q alone is V, the total potential at P is:
A.
V/2
B.
V
C.
2V
D.
3V
Correct Answer:
2V
Explanation:
The first charge produces V = kq/r. The second produces k(2q)/(2r) = V. Therefore, the total potential is V + V = 2V.
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