Electric Charges & Fields
Q. What happens to the electric field if the charge is tripled while keeping the distance constant?
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A.
It triples
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B.
It halves
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C.
It remains the same
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D.
It quadruples
Solution
The electric field is directly proportional to the charge. Tripling the charge will triple the electric field.
Correct Answer: A — It triples
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Q. What happens to the electric field inside a conductor in electrostatic equilibrium?
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A.
It is zero
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B.
It is constant
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C.
It varies linearly
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D.
It is maximum at the center
Solution
In electrostatic equilibrium, the electric field inside a conductor is zero.
Correct Answer: A — It is zero
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Q. What happens to the electric field strength if the distance from a point charge is tripled?
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A.
It becomes one-third
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B.
It becomes one-ninth
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C.
It becomes three times
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D.
It remains the same
Solution
The electric field strength E ∝ 1/r², so if distance is tripled, the field strength becomes 1/9 of the original.
Correct Answer: B — It becomes one-ninth
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Q. What is the direction of the electric field due to a negative point charge?
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A.
Away from the charge
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B.
Towards the charge
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C.
Perpendicular to the charge
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D.
None of the above
Solution
The electric field due to a negative charge points towards the charge.
Correct Answer: B — Towards the charge
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Q. What is the direction of the electric field due to a positive charge?
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A.
Towards the charge
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B.
Away from the charge
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C.
Perpendicular to the charge
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D.
None of the above
Solution
The electric field due to a positive charge points away from the charge.
Correct Answer: B — Away from the charge
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Q. What is the electric field at a distance of 1m from a charge of +1μC?
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A.
9 × 10^9 N/C
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B.
9 × 10^6 N/C
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C.
9 × 10^3 N/C
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D.
9 × 10^12 N/C
Solution
Electric field E = k * q / r^2 = (9 × 10^9) * (1 × 10^-6) / (1)^2 = 9 × 10^3 N/C.
Correct Answer: B — 9 × 10^6 N/C
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Q. What is the electric field at a point due to a positive charge?
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A.
Directed towards the charge
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B.
Directed away from the charge
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C.
Zero
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D.
Depends on the distance from the charge
Solution
The electric field due to a positive charge is directed away from the charge.
Correct Answer: B — Directed away from the charge
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Q. What is the electric field at a point midway between two equal and opposite charges?
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A.
Zero
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B.
Maximum
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C.
Minimum
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D.
Depends on distance
Solution
The electric fields due to both charges cancel each other out at the midpoint, resulting in zero electric field.
Correct Answer: A — Zero
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Q. What is the electric field due to a point charge of +5μC at a distance of 0.1 m?
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A.
4500 N/C
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B.
5000 N/C
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C.
5500 N/C
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D.
6000 N/C
Solution
Electric field E = k * |q| / r² = (9 × 10^9 N m²/C²) * (5 × 10^-6 C) / (0.1 m)² = 4500 N/C.
Correct Answer: B — 5000 N/C
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Q. What is the electric field due to a point charge of +5μC at a distance of 0.3m? (2000)
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A.
1500 N/C
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B.
5000 N/C
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C.
1000 N/C
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D.
2000 N/C
Solution
E = k * |q| / r^2 = (9 × 10^9) * (5 × 10^-6) / (0.3)^2 = 5000 N/C.
Correct Answer: B — 5000 N/C
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Q. What is the electric field inside a uniformly charged spherical shell?
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A.
Zero
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B.
Uniform
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C.
Varies linearly
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D.
Depends on the charge outside
Solution
The electric field inside a uniformly charged spherical shell is zero.
Correct Answer: A — Zero
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Q. What is the potential difference between two points A and B in an electric field if the work done in moving a charge of +2C from A to B is 10J?
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A.
5 V
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B.
10 V
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C.
20 V
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D.
2 V
Solution
V = W/Q = 10 J / 2 C = 5 V.
Correct Answer: B — 10 V
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Q. What is the potential difference between two points A and B in an electric field of 200 N/C if the distance between them is 0.5 m?
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A.
100 V
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B.
200 V
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C.
50 V
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D.
25 V
Solution
Potential difference V = E * d = 200 N/C * 0.5 m = 100 V.
Correct Answer: A — 100 V
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Q. What is the potential difference between two points in a uniform electric field of strength 200 N/C separated by 3m?
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A.
600 V
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B.
200 V
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C.
300 V
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D.
400 V
Solution
V = E * d = 200 N/C * 3 m = 600 V.
Correct Answer: A — 600 V
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Q. What is the potential difference between two points in an electric field if the work done to move a charge of 2C is 10J?
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A.
5V
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B.
20V
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C.
2V
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D.
10V
Solution
Potential difference V = W/Q = 10J / 2C = 5V.
Correct Answer: B — 20V
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Q. What is the potential difference between two points in an electric field if the work done in moving a charge of +2μC is 0.04 J?
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A.
20 V
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B.
10 V
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C.
5 V
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D.
2 V
Solution
Potential difference V = W/q = 0.04 J / (2 × 10^-6 C) = 20 V.
Correct Answer: A — 20 V
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Q. What is the potential difference between two points in an electric field if the work done in moving a charge of +2μC between them is 0.04 J?
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A.
20 V
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B.
10 V
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C.
5 V
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D.
2 V
Solution
V = W/q = 0.04 J / (2 × 10^-6 C) = 20 V.
Correct Answer: A — 20 V
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Q. What is the potential energy of a system of two charges +3μC and +4μC separated by 0.2m?
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A.
0.54 J
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B.
0.72 J
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C.
0.36 J
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D.
0.18 J
Solution
U = k * (q1 * q2) / r = (9 × 10^9) * (3 × 10^-6 * 4 × 10^-6) / 0.2 = 0.54 J.
Correct Answer: B — 0.72 J
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Q. What is the potential energy of a system of two charges +3μC and +5μC separated by 0.2m?
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A.
-6.75 J
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B.
6.75 J
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C.
0.75 J
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D.
-0.75 J
Solution
Potential energy U = k * (q1 * q2) / r = (9 × 10^9) * (3 × 10^-6) * (5 × 10^-6) / 0.2 = 6.75 J.
Correct Answer: B — 6.75 J
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Q. What is the potential energy of a system of two charges +3μC and -5μC separated by 0.3m?
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A.
-0.45 J
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B.
0.45 J
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C.
-0.15 J
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D.
0.15 J
Solution
Potential energy U = k * q1 * q2 / r = (9 × 10^9) * (3 × 10^-6) * (-5 × 10^-6) / 0.3 = -0.45 J.
Correct Answer: A — -0.45 J
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Q. What is the potential energy of a system of two charges +5μC and +10μC separated by 0.2m?
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A.
-0.225 J
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B.
0.225 J
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C.
0.45 J
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D.
0.9 J
Solution
Potential energy U = k * (q1 * q2) / r = (9 × 10^9) * (5 × 10^-6) * (10 × 10^-6) / 0.2 = 0.225 J.
Correct Answer: B — 0.225 J
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Q. What is the potential energy of a system of two charges +q and +q separated by a distance r?
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A.
0
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B.
k*q²/r
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C.
-k*q²/r
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D.
2k*q²/r
Solution
Potential energy U = k * (q1 * q2) / r = k * (q * q) / r = k*q²/r.
Correct Answer: B — k*q²/r
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Q. What is the work done in moving a charge of +2μC from a point A to B in a uniform electric field of 500 N/C over a distance of 0.4m?
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A.
400 J
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B.
200 J
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C.
100 J
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D.
80 J
Solution
Work done W = F * d = q * E * d = (2 × 10^-6 C) * (500 N/C) * (0.4 m) = 0.4 J = 80 J.
Correct Answer: D — 80 J
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Q. What is the work done in moving a charge of +2μC through a potential difference of 10V?
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A.
20 μJ
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B.
200 μJ
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C.
2 μJ
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D.
0.2 μJ
Solution
W = q * V = 2 × 10^-6 C * 10 V = 20 × 10^-6 J = 20 μJ.
Correct Answer: B — 200 μJ
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Q. Which of the following statements is true about electric field lines?
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A.
They can cross each other
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B.
They are always straight
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C.
They point from positive to negative
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D.
They are always circular
Solution
Electric field lines point from positive to negative charges and never cross each other.
Correct Answer: C — They point from positive to negative
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Q. Which of the following statements is true regarding electric field lines?
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A.
They can cross each other
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B.
They are always straight
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C.
They point from positive to negative charges
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D.
They are always circular
Solution
Electric field lines point from positive to negative charges and never cross each other.
Correct Answer: C — They point from positive to negative charges
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