12th Class Physics MCQs Preparation 2022 and Onwards (Unit:  Electrostatics : Set-1 (30 MCQs)) for National MDCAT, ECAT, FPSC, PPSC, JOB Exam, Physics Lecturer, SSC, HSSC (F.Sc.), BS, MS Exams NTS, ETS, etc..



1. The electrostatic force between two point charges is independent of one of the following quantities




... Answer is B. Temperature of the charges
F = `\frac {1}{4ㅈƐ_0}``\frac {q_1q_2}{r^2}`


2. If the distance between two equal charges is reduced to half and the magnitude of charges is also decreased to half, then the force between them will be




... Answer is A. Remain same
F = `\frac {1}{4ㅈƐ_0}``\frac {q_1q_2}{r^2}`


3. The concept of the electric field was introduced by




... Answer is B. Faraday
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4. The number of electrons or protons which constitutes a charge of one coulomb is




... Answer is B. 6.25 ｘ10¹⁸
1 C of charge is contained in `\frac {1}{1.6 x 10^{-19}}`= 6.25 x 10¹⁸. Therefore, 6 x 10¹⁸ electrons constitute one coulomb of charge.


5.  For static electricity the value of relative permittivity is always




... Answer is C. Greater than one
`\Ɛ_r` = `\frac {Ɛ}{Ɛ_0}` is always greater than one for all material (for vacuum its value is 1).


6. A metallic charged sphere is placed in uniform electric field E, the electric field inside the sphere will be




... Answer is D. Zero
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7. The electric intensity E at a point in a field due to a dipole depends upon distance 'r' the relationship between them is :




... Answer is C. E ∝ `\frac {1}{r^2}`
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8. The dipole moment is defined as the product of




... Answer is A. Charge and distance
P =qd


9. Debye is the unit of




... Answer is D. Dipole moment
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10. The electric flux is maximum when the angle 'θ' between the area vector and electric intensity is




... Answer is A. 0°
ዋ = E ΔA cos ፀ


11. Electric flux is independent of one of the following quantities.




... Answer is D. Distance
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12. The dimension of electric potential is the same as that of




... Answer is B. Work per unit charge
The dimension of an electric potential is [M¹ L² T-³ I⁻¹], work is [M¹ L² T-²] and q is [T-¹ I¹]


13. Electron volt is the unit of

... Answer is A. Energy
One electron volt (1 eV) equals 1.602 × 10−12 erg or 1.602 × 10−19 joule.


14.  The energy of an electron which accelerates through a potential difference of 1000 V is




... Answer is D. 1.6 ｘ10⁻¹⁶ J
Energy gained by electron = V e = 1000 Vｘ1.6 ｘ10⁻¹⁹ J = 1.6 ｘ10⁻¹⁶ J


15. The unit of surface charge density is




... Answer is D. C m⁻²
σ = `\frac {q}{A}`


16.. Capacitance of a capacitor does not depend upon




... Answer is D. Material of the plates
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17. In the presence of dielectric material, the electric field between the plates of the capacitor will be :




... Answer is C. Decreased
The strength of the electric field is reduced due to the presence of a dielectric.


18. When the potential difference across the capacitor is decreased by dielectric then the capacitance of the capacitor will be




... Answer is D. Increase
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19. The unit of the product of resistance and capacitance is equal to a unit of




... Answer is A. Time
Resistance ｘ Capacitance = `\V/I ｘ q/V` = `\q/I` = t


20. A capacitor is approximately full charged after




... Answer is D. Five-times constant
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21. The electric potential between two points A and B are ΔV. The work done W by the field in moving a charge from A to B is




... Answer is C. W = qΔV
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22. Two parallel metal plates are 8.00 m apart. The electric field between the plates is uniform, directed toward the right, and has a magnitude of 4.00 N/C. If an ion of charge +2e is released at rest at the left-hand plate, what is its kinetic energy when it reaches the right-hand plate?




... Answer is B. 64 eV
🛆 K.E = q 🛆V where 🛆V = E. 🛆r So 🛆 K.E = q (E. 🛆r) = 2e x 4 N/C x 8 m = 64 eV


23. In the figure below, the charge on the 3 µF capacitors is




... Answer is B. 10 µC
Using Q = Ce V and Ce = 1/C1 +1/C2 + 1/C3 -------In book options are given in F (farad) which is incorrect because we are asked to find Charge so replace F with C.


24. A microfarad capacitor of a TV is subjected to a 4000 V potential difference. The energy stored in the capacitor is




... Answer is A. 8 J
using formula U = 1/2 CV²


25.  The electric flux through the surface of a sphere due to a charge q placed at its centre depends upon




... Answer is D. the quantity of charge inside the sphere
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26. An electric charge q is placed at the centre of a cube of the side "a". The electric flux on its one side will be




... Answer is A. `\frac {q}{ε₀a²}`
Gauss's law ф = Q /ε₀ Cube has 6 face For one face ф = (1/6)(Q /ε₀) = q/6ε₀


27. The electric field at a distance of 20 cm from 2 µC charges is: :




... Answer is A. 3ｘ10⁵ N
E = `\ frac{Kq}{r^2}` by putting values we get E = 4.5ｘ10⁵ All the options given in the are wrong so replace anyone let option A with 4.5ｘ10⁵ N


28. A proton is about 1840 times heavier than an electron. When accelerated by a potential difference if 1 kV, it's kinetic energy will be:




... Answer is C. 1 kev
--------🛆U = 🛆 K.E = q 🛆V when q = 1 e ans 🛆V = 1 kV so 🛆 K.E = 1 keV​


29. The unit of Electric field intensity is :




... Answer is D. All of these
Volt/metre, newton/Coulomb and (Joule/ Coulomb).metre are all units of E, So replace it with all of these.


30. Some charge is given to a conductor. Then it's potential




... Answer is C. Is remain the same throughout the conductor
E = 🛆V/🛆A -- inside the conductor E = 0 ----🛆V = 0 V₂ = V₁




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