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 point charges produce electric fields of 4 N/C and 3 N/C at a point, both in the same direction. What is the resultant electric field at that point?
A.
1 N/C
B.
3 N/C
C.
7 N/C
D.
12 N/C
Correct Answer:
7 N/C
Explanation:
By the superposition principle, electric fields add vectorially. Since both fields are in the same direction, the resultant field is 4 + 3 = 7 N/C.
2. Two electric fields of magnitudes 8 N/C and 5 N/C act in opposite directions at a point. What is the magnitude of the resultant electric field?
A.
3 N/C
B.
5 N/C
C.
13 N/C
D.
40 N/C
Correct Answer:
3 N/C
Explanation:
For opposite directions, the resultant magnitude is the difference of the two fields: 8 − 5 = 3 N/C.
3. At a point, three charges produce electric fields of 2 N/C, 3 N/C, and 4 N/C, all along the same direction. What is the total electric field?
A.
1 N/C
B.
5 N/C
C.
9 N/C
D.
24 N/C
Correct Answer:
9 N/C
Explanation:
The net electric field is the vector sum of the fields due to all charges. Since all three fields have the same direction, their magnitudes add to give 2 + 3 + 4 = 9 N/C.
4. Two identical 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:
The two positive charges produce equal electric fields at the midpoint in opposite directions. These fields cancel by superposition, giving zero net electric field.
5. Two equal and opposite charges are placed symmetrically on either side of a point between them. What is the direction of the net electric field at that point?
A.
Toward the positive charge
B.
Toward the negative charge
C.
Perpendicular to the line joining the charges
D.
Zero in all cases
Correct Answer:
Toward the negative charge
Explanation:
The electric field due to the positive charge points away from it, and the field due to the negative charge points toward it. At the point between them, both fields point toward the negative charge and therefore add in that direction.
6. At a point, the electric field due to charge q1 is 6 N/C east and that due to charge q2 is 6 N/C west. What is the resultant electric field?
A.
12 N/C east
B.
12 N/C west
C.
6 N/C east
D.
Zero
Correct Answer:
Zero
Explanation:
The two electric fields have equal magnitudes and opposite directions, so their vector sum is zero.
7. A point is affected by electric fields of 5 N/C north and 12 N/C east. What is the magnitude of the resultant electric field?
A.
7 N/C
B.
13 N/C
C.
17 N/C
D.
60 N/C
Correct Answer:
13 N/C
Explanation:
The two fields are perpendicular, so the resultant magnitude is calculated using the Pythagorean theorem: √(5² + 12²) = √169 = 13 N/C.
8. Which expression gives the net electric field at a point due to three charges?
A.
The product of the three individual electric fields
B.
The average of the three individual electric fields
C.
The vector sum of the three individual electric fields
D.
The largest individual electric field only
Correct Answer:
The vector sum of the three individual electric fields
Explanation:
The superposition principle states that the total electric field due to multiple charges is the vector sum of the electric fields produced by each charge separately.
9. At a point, the electric field due to one charge is 20 N/C east and the field due to another charge is 15 N/C west. What is the direction of the resultant electric field?
A.
East
B.
West
C.
North
D.
The resultant field is zero
Correct Answer:
East
Explanation:
The fields act in opposite directions, but the eastward field is larger. Therefore, the resultant electric field points east, with magnitude 20 − 15 = 5 N/C.
10. Two positive charges are placed near each other. At a point between them, the electric fields due to the two charges are in opposite directions. What is the net electric field at that point?
A.
The sum of the two electric field magnitudes
B.
The difference of the two electric field magnitudes
C.
Always zero
D.
The product of the two electric field magnitudes
Correct Answer:
The difference of the two electric field magnitudes
Explanation:
By the superposition principle, electric fields are added as vectors. Since the two fields are in opposite directions, their net magnitude is the difference of their magnitudes.