101. Unlike charges:
- exert no force
- attract each other
- become neutral
- repel each other
Answer: B) attract each other
Explanation: Basic law of charges. SLO P-11-E-07 · Application
MCQs / Physics / Electrostatics
Electrostatics MCQs — Physics (page 5)
120 multiple-choice questions on Electrostatics from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.
102. A Faraday cage does NOT protect against:
- static magnetic fields (e.g. from a bar magnet)
- external static electric fields
- lightning strikes
- radio interference
Answer: A) static magnetic fields (e.g. from a bar magnet)
Explanation: A conducting cage doesn't screen steady magnetic fields. SLO P-11-E-06 · Understanding
103. A charged sphere's field lines outside it are:
- circular
- radial, like those of a point charge
- absent
- parallel
Answer: B) radial, like those of a point charge
Explanation: Spherical symmetry. SLO P-11-E-05 · Knowledge
104. The electric field around an isolated positive charge points:
- towards the nearest negative charge only
- radially inward
- radially outward
- in circles
Answer: C) radially outward
Explanation: Away from positive charges. SLO P-11-E-01 · Knowledge
105. A neutral point in an electric field is where:
- charges are created
- the field is maximum
- the resultant field is zero
- field lines start
Answer: C) the resultant field is zero
Explanation: Fields cancel. SLO P-11-E-03 · Understanding
106. The field strength of a point charge and Coulomb's law are linked because:
- E = kQqr
- E = Fq
- E = kQr^2
- E = Fq = kQq/r^2q = kQr^2
Answer: D) E = Fq = kQq/r^2q = kQr^2
Explanation: Divide the Coulomb force by the test charge. SLO P-11-E-08 · Application
107. A charge of 3 10^-6 C is placed in an electric field of 400 N/C. The force on it is:
- 0.0024 N
- 0.012 N
- 0.0012 N
- 1.2 10^-4 N
Answer: C) 0.0012 N
Explanation: F = qE = 3 10^-6 400 = 0.0012 N. SLO P-11-E-02 · Application
108. Halving the separation of parallel plates (same p.d.) makes the field strength:
- half
- unchanged
- double
- four times
Answer: C) double
Explanation: E propto 1/d. SLO P-11-E-02 · Application
109. The field lines around an isolated point charge are:
- parallel lines
- concentric circles
- radial straight lines
- spirals
Answer: C) radial straight lines
Explanation: Spread equally in all directions. SLO P-11-E-03 · Understanding
110. The electric field strength 5.3 10^-11 m from a point charge of 1.6 10^-19 C in free space is:
- 2.56 10^11 N/C
- 1.02 10^12 N/C
- 5.12 10^11 N/C
- 27.1 N/C
Answer: C) 5.12 10^11 N/C
Explanation: E = kQr^2 = 8.99 10^9 1.6 10^-19(5.3 10^-11)^2 = 5.12 10^11 N/C. SLO P-11-E-08 · Application
111. The electric field strength 0.3 m from a point charge of 2 10^-6 C in free space is:
- 2 10^5 N/C
- 99,900 N/C
- 59,900 N/C
- 4 10^5 N/C
Answer: A) 2 10^5 N/C
Explanation: E = kQr^2 = 8.99 10^9 2 10^-6(0.3)^2 = 2 10^5 N/C. SLO P-11-E-08 · Application
112. Charges of 1.6 10^-19 C and 1.6 10^-19 C are 1 10^-10 m apart in free space. The force between them is (k = 8.99 10^9 N m^2 C^-2):
- 2.3 10^-18 N, repulsive
- 2.3 10^-8 N, attractive
- 4.6 10^-8 N, repulsive
- 2.3 10^-8 N, repulsive
Answer: D) 2.3 10^-8 N, repulsive
Explanation: F = kq1q2r^2 = 2.3 10^-8 N; like charges repel. SLO P-11-E-07 · Application
113. Field lines from a positive and a negative charge (a dipole):
- form closed loops round each charge
- never connect
- go from the positive charge to the negative charge
- go from negative to positive
Answer: C) go from the positive charge to the negative charge
Explanation: Curved lines joining them. SLO P-11-E-03 · Understanding
114. Electric field lines show:
- the path of light
- the force on a neutron
- the direction of a current
- the direction of the force on a positive charge
Answer: D) the direction of the force on a positive charge
Explanation: Lines of force. SLO P-11-E-03 · Understanding
115. The force between two charges in a medium other than vacuum is:
- smaller than in a vacuum
- zero
- the same
- larger than in a vacuum
Answer: A) smaller than in a vacuum
Explanation: Divided by the relative permittivity. SLO P-11-E-07 · Application
116. Charges of 1 10^-6 C and 1 10^-6 C are 1 m apart in free space. The force between them is (k = 8.99 10^9 N m^2 C^-2):
- 0.00899 N, repulsive
- 0.018 N, repulsive
- 0.00900 N, repulsive
- 0.00899 N, attractive
Answer: A) 0.00899 N, repulsive
Explanation: F = kq1q2r^2 = 0.00899 N; like charges repel. SLO P-11-E-07 · Application
117. Between two parallel plates, the electric field is:
- uniform (same everywhere except near the edges)
- radial
- zero
- strongest at the centre only
Answer: A) uniform (same everywhere except near the edges)
Explanation: Parallel, equally spaced field lines. SLO P-11-E-02 · Application
118. Charges of 5 10^-9 C and -4 10^-9 C are 0.02 m apart in free space. The force between them is (k = 8.99 10^9 N m^2 C^-2):
- 8.99 10^-6 N, attractive
- 4.49 10^-4 N, repulsive
- 8.99 10^-4 N, attractive
- 4.49 10^-4 N, attractive
Answer: D) 4.49 10^-4 N, attractive
Explanation: F = kq1q2r^2 = 4.49 10^-4 N; unlike charges attract. SLO P-11-E-07 · Application
119. Charges of 4 10^-6 C and -2 10^-6 C are 0.3 m apart in free space. The force between them is (k = 8.99 10^9 N m^2 C^-2):
- 1.6 N, attractive
- 0.24 N, attractive
- 0.799 N, attractive
- 0.799 N, repulsive
Answer: C) 0.799 N, attractive
Explanation: F = kq1q2r^2 = 0.799 N; unlike charges attract. SLO P-11-E-07 · Application
120. If the distance between two charges is doubled, the force becomes:
- one quarter
- double
- half
- four times
Answer: A) one quarter
Explanation: Inverse square. SLO P-11-E-07 · Application
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