physics : class12 Electric Field Due to Multiple Charges : Superposition Principle : Electrostatics MCQ Questions and Answers
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Electric Field Due to Multiple Charges
MCQ questions and answers.
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MCQ Questions
1. Two equal positive charges are placed symmetrically on either side of a point. What is the net electric field at the midpoint between them?
A.
Zero
B.
Directed toward the left charge
C.
Directed toward the right charge
D.
Directed away from both charges
Correct Answer:
Zero
Explanation:
At the midpoint, the two charges produce electric fields of equal magnitude in opposite directions, so their vector sum is zero.
2. Two positive point charges produce electric fields of magnitudes 4 N/C and 3 N/C at a point, in the same direction. What is the net electric field?
A.
1 N/C
B.
7 N/C
C.
12 N/C
D.
0.75 N/C
Correct Answer:
7 N/C
Explanation:
Since the two electric field vectors are in the same direction, their magnitudes add: 4 N/C + 3 N/C = 7 N/C.
3. Two charges produce electric fields of 8 N/C and 5 N/C at a point in opposite directions. What is the magnitude of the net electric field?
A.
13 N/C
B.
40 N/C
C.
3 N/C
D.
0 N/C
Correct Answer:
3 N/C
Explanation:
For opposite electric field directions, the net magnitude is the difference between the two magnitudes: 8 N/C - 5 N/C = 3 N/C.
4. At a point, two electric field vectors of equal magnitude act at right angles to each other. If each has magnitude E, the net electric field magnitude is
A.
E/2
B.
E
C.
2E
D.
E√2
Correct Answer:
E√2
Explanation:
Perpendicular electric field vectors combine using the Pythagorean theorem: the net magnitude is √(E² + E²) = E√2.
5. A positive charge and a negative charge are placed at equal distances from a midpoint. The electric fields at the midpoint are directed
A.
In the same direction
B.
In opposite directions
C.
At right angles
D.
Both equal to zero
Correct Answer:
In the same direction
Explanation:
At the midpoint, the field due to the positive charge points away from it, while the field due to the negative charge points toward it. These directions are the same along the line joining the charges.
6. If the electric field due to charge q1 at a point is E1 and that due to charge q2 is E2, the net field is represented by
A.
E1 + E2 as ordinary numbers only
B.
E1 - E2 in every situation
C.
The vector sum E1 + E2
D.
E1 × E2
Correct Answer:
The vector sum E1 + E2
Explanation:
Electric field is a vector quantity, so the fields due to individual charges must be added vectorially.
7. Three charges produce electric fields of 2 N/C, 3 N/C, and 4 N/C at a point, all in the same direction. What is the net electric field?
A.
1 N/C
B.
5 N/C
C.
9 N/C
D.
24 N/C
Correct Answer:
9 N/C
Explanation:
Because all three fields point in the same direction, their magnitudes are added: 2 + 3 + 4 = 9 N/C.
8. The net electric field at a point due to multiple charges can be found by first calculating
A.
The electric field due to each charge separately
B.
Only the field due to the nearest charge
C.
The total charge and ignoring positions
D.
The product of all charge values
Correct Answer:
The electric field due to each charge separately
Explanation:
The superposition principle requires calculating the individual electric field contribution of every charge and then adding those contributions as vectors.
9. Two identical positive charges are placed symmetrically about a point. The vertical components of their electric fields at that point are equal in magnitude and opposite in direction. Their vertical resultant is
A.
Twice one component
B.
Equal to one component
C.
Zero
D.
Four times one component
Correct Answer:
Zero
Explanation:
Equal and opposite components cancel when added vectorially, so the resultant vertical electric field component is zero.