MCQGeeks
0 : 0 : 1
CBSE
JEE
NTSE
NEET
English
UK Quiz
Quiz
Driving Test
Practice
Games
NEET
Physics NEET MCQ
Electrostatics Mcq
Quiz 9
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Q.1
Two charges 4q and q are placed 30cm apart. At what point the value of electric field will be zero
0%
a) 10 cm away from and between the charges
0%
b) 20 cm away from q and between the charge
0%
c)10 cm away from q and outside the line joining the charge
0%
d)10 cm away from 4q and out side the line joining them
Explanation
k(4q) / x2=kq/(30-x)2 on simplification2/x=1 / (30 - x) x=10 cm Answer:(a)
Q.2
If Q=2 C and force on it is F=10 N. Then the value of field intensity will be
0%
a) 100 N/C
0%
b) 50 N/C
0%
c) 200 N/C
0%
d) 10 N/C
Explanation
Answer: (b)
Q.3
Two similar charges of +Q as shown in figure are placed at A and B, -q charge is placed at point C midway between A and B. -q charge will oscillate if
0%
a) it is moved towards A
0%
b) it is moved towards B
0%
c)it is moved upwards AB
0%
d)distance between A and B is reduced
Explanation
Answer:(c)
Q.4
A thin metal plate P is inserted between the plates of a parallel -plate capacitor of capacitance C in such a way that its edges touches the two plates. The capacitance now becomes
0%
a) C/2
0%
b) 2C
0%
c) 0
0%
d) ∞
Explanation
due to thin plate in contact with both plates d=0 C=εoA/ d since d=0 C=∞ Answer: (d)
Q.5
An accelerated or decelerated charges produces
0%
a)electric field only
0%
b) magnetic field only
0%
c)localised electric and magnetic fields
0%
d)A stationary charge produces both electric and magnetic fields
Explanation
Answer: (d)
Q.6
Two point charges is air at a distance of 20 cm from each other interact with a certain force. At what distance from each other should these charges be placed in oil of relative permitivity 5 to obtain the same force of interaction
0%
a) 8.94×10-2 m
0%
b) 0.894×10-2 m
0%
c)89.4×10-2 m
0%
d)8.94×102 m
Explanation
distance d in air then equivalent distance with dielectric=d /√(k)here k is dielectric constant thus d'=20/√5 cm=8.93cm ≈8.94×10-2 mAnswer: (a)
Q.7
The force between two point charges placed in vacuum is 18N at separation of 1mm. If a glass plate of thickness 1mm and dielectric constant 6 be kept between the charges then the force between them would be
0%
a) 18 N
0%
b) 108N
0%
c)3 N
0%
d)3×10-6N
Explanation
F'=F/k Answer:(c)
Q.8
A pendulum bob of mass 80mg and carrying a charge of 2×10-8 C is at rest in a horizontal uniform electric field of 20,000 N/m. Find the tension in the thread of pendulum
0%
a) 8.8 × 10-2 N
0%
b) 8.8 × 10-3 N
0%
c) 8.8 × 10-4 N
0%
d) 8.8 × 10-5 N
Explanation
Because of horizontal electric field and down direction gravitational field boob will make an angle with horizontal as shown in figure From diagram Tcosθ=mg and Tsinθ=q E solve above two equations to get T Answer: (c)
Q.9
Six charges +Q each are placed at the corners of a regular hexagon of side 'a', the electric field at the centre of hexagon is
0%
a)zero
0%
b) 6KQ2 / a2
0%
c)KQ2 / a2
0%
d)6KQ2 / (√2×a2)
Explanation
Because of symmetry of charges around centre electric field is zeroAnswer: (a)
Q.10
Two charged sphere A and B are charged with the charges of +10 C and +20 C respectively and separated by a distance of 80 cm. The electric field at a point on the line joining the center of the two spheres will be zero at a distance from sphere A..
0%
a) 20 cm
0%
b) 33 cm
0%
c)55 cm
0%
d)60 cm
Explanation
Answer: (b)
Q.11
The electric field inside a spherical shell of uniform surface charge density is
0%
a) zero
0%
b) constant, but non zero
0%
c)proportional to the distance from centre
0%
d)non of the above
Explanation
Answer:(a)
Q.12
If the electric field is uniform, then the electric lines of forces are
0%
a) Divergent
0%
b) Convergent
0%
c) Circular
0%
d) Parallel
Explanation
Answer: (d)
Q.13
Electric lines of forces
0%
a)Exists everywhere
0%
b) Are imaginary
0%
c)Exist only in the immediate vicinity of electric charges
0%
d)None of the above
Explanation
Answer: (b)
Q.14
Charge reside on the
0%
a) Outer surface of the charged conductor
0%
b) Inner surface of charged conductor
0%
c)Inner as well as outer surface of the charged conductor
0%
d)None of the above
Explanation
Answer: (a)
Q.15
In an electric field the work done in moving a unit positive charge between two points is the measure of
0%
a) Resistance
0%
b) Potential difference
0%
c) Intensity of electric field
0%
d)Capacitance
Explanation
Answer:(b)
Q.16
A ring of radius R carries a uniformly distributed charge +Q . A point charge -q is placed on the axis of the ring at a distance 2R from the centre of the ring and released from rest. The particle
0%
a) BEcomes in rest condition immediately
0%
b) Execute simple harmonic motion
0%
c) Motion is not SHM
0%
d) come at the centre of the ring immediately
Explanation
Answer: (c)
Q.17
The ratio of the electric field due to an electric dipole on its axis and on the perpendicular bisector of the dipole is
0%
a)1:2
0%
b) 2:1
0%
c)1:4
0%
d)4:1
Explanation
Answer: (b)
Q.18
Which of the following charge is not possible
0%
a) 1.6×10-18C
0%
b) 1.6×10-19C
0%
c)1.6×10-20C
0%
d)None of these
Explanation
Q=neAnswer: (c)
Q.19
A point charge q1 exerts a force F on qAn equal charge q3 is now kept near qThe resultant force on q2 due to q1 will be
0%
a)F
0%
b)2F
0%
c)F/2
0%
d)-F
Explanation
Electric force is two body force Answer:(a)
Q.20
Two charged spheres of radius R are kept at a distance d ( d >2R). One has a charge +q and other -q. The force between them will be
0%
a) KQ2 / d2
0%
b) > KQ2 / d2
0%
c) < KQ2 / d2
0%
d) None of these
Explanation
Answer: (b)
Q.21
A metal sphere us placed in an uniform electric field which one is a correct electric line of force
0%
a)1
0%
b) 2
0%
c)3
0%
d)4
Explanation
Answer: (d)
Q.22
A charged particle is free to move in electric field will it always move along the electric field lines of force
0%
a) yes, always
0%
b) some times
0%
c)never
0%
d)no, if V is inclined to field
Explanation
Answer: (d)
Q.23
What will be the change in potential energy of q3, in moving it along CD for the following figure q1=q2=40nC and q3=20nC
0%
a)3 ×10-7 J
0%
b) -3 ×10-7 J
0%
c)2.88 ×10-7 J
0%
d)1.88 ×10-3 J
Explanation
Answer:(c)
Q.24
In following figure, where the charge q must be kept, so that the potential energy of the system will be minimum
0%
a) x=1 cm
0%
b) x=4 cm
0%
c) x=3 cm
0%
d) x=2 cm
Explanation
when system is in equilibrium potential energy is minimum thus calculate force on charge q due to remaining two charges and equate it to zero solve equation for x Answer: (c)
Q.25
The charges of 10µC each are kept at three corners of an equilateral triangle of 10cm side. What is the potential energy of system?
0%
a)27 J
0%
b) -27J
0%
c)20J
0%
d)0 J
Explanation
Answer: (a)
Q.26
A electron ( mass m, charge e) is accelerated through a potential difference of V volts. Find the final velocity of electrons
0%
a) v=√ (2eV/m)
0%
b) v=√(eV/m)
0%
c)v=√(m/eV)
0%
d)v=√(m/2eV)
Explanation
Answer: (a)
Q.27
Three charges 2q, -q, -q are located at the vertices of an equilateral triangle. At the circumcentre of the triangle
0%
a) The field is zero but potential is not zero
0%
b) The field is non-zero but the potential is zero
0%
c)Both, field and potential are zero
0%
d)Both, field and potential are non-zero
Explanation
Answer:(b)
Q.28
A proton is released from rest towards an another proton with a velocity of 7.45×105 m/s. The minimum approach is
0%
a) 10-12 m
0%
b) 10-14 m
0%
c) 10-10 m
0%
d) 10-8 m
Explanation
Use K. E=PE and solve equation for r Answer: (a)
Q.29
A particle of mass 6µg carrying a charge of 10-9C is placed in the electric field of strength E = 6×105 V/m, the acceleration acquired by the particle is
0%
a) 102 m/sec2
0%
b) 105 m/sec2
0%
c) 103 m/sec2
0%
d) 1020 m/sec2
Explanation
acceleration a = Eq/m Answer: (b)
Q.30
Two small balls having equal positive charge Q on each are suspended by two insulating strings at equal length L meter, from a hook fixed to stand. The whole set up is taken in a satellite into space where there is no gravity. Then the angle θ between two strings and tension in each string is
0%
a) 0, K(q/L)2
0%
b) π,(K/2)(q/L)2
0%
c) π,(K/4)(q/L)2
0%
d) π/2, (K/2)(q/L)2
Explanation
in absence of gravity only electrostatic repulsive force is present angle becomes π And Tension = force between two charged balls Answer: (c)
Q.31
Three charges -q1, +q2, -q3 are placed as shown in figure. The x -componant of force on -q1 is proportional to
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Force on -q1 due to q2 is along x axis Force on -q1 due to -q3 is along x axis Answer:(c)
Q.32
there is an electric field E in X direction. IF the work done on moving a charge 0.2C through a distance of 2m along a line making an angle 60° with the x-axis is 4.0, what is the value of E
0%
a)√3 N/C
0%
b) 4 N/C
0%
c)5 N/C
0%
d)none of these
Explanation
W=Eq ×(lcos60) 4=E (0.2)(2cos60) 4=E (0.2) E=4/0.2=20 N/CAnswer: (d)
Q.33
The electric field at a point on equatorial line of a dipole and direction of the dipole moment
0%
a) will be parallel
0%
b) will be in opposite direction
0%
c)will be perpendicular
0%
d)are not related
Explanation
Answer: (b)
Q.34
Two identical small balls each of mass, are suspended by two light inelastic conducting threads each of length l from the same fixed point support. If the distance (d) between two balls is very less the d is equal to
0%
a)
0%
b)
0%
c)
0%
d) none oth these
Explanation
FE Coulombic force between two eqaul charges = KQ2 /d2 From diagram since θ is very small tanθ = sinθ from figure sinθ = (d/2) / l comparing equations we get Answer: (a)
Q.35
A metal sphere A of radius R has a charge of Q on it. The field at point B outside the sphere is E. Now another sphere of radius R having a charge -Q is placed at point B. The total field at a point midway between A and B due to both sphere is
0%
a)4E
0%
b) 8E
0%
c)12E
0%
d)16E
Explanation
Answer: (d)
Q.36
A uniformly charged rod with charge per unit length λ is bent in to the shape of a semicircle of radius R. The electric field at the centre is
0%
a) 2Kλ / R
0%
b) Kλ / 2R
0%
c)Zero
0%
d)None
Explanation
Answer: (c)
Q.37
A cylinder of radius R and length L is placed in a uniform electric field E parallel to the axis of cylinder, the total flux for the surface of the cylinder is given by
0%
a) 2πR2E
0%
b) πR2 / E
0%
c)2πR2 / E
0%
d)zero
Explanation
Answer:(d)
Q.38
Electric potential in an electric field is given by V=K/r ( K being constant), if position vector r=2i+3j +6k then electric field will be
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
We know that E=-dV/dr Answer: (b)
Q.39
The electric field at the surface of a charged spherical conductor is 10kV/m. The electric field at a distance equal to the diameter from the centre will be
0%
a)2.5 V/m
0%
b) 2.5 kV/m
0%
c)5.0 kV/m
0%
d)5.0V/,
Explanation
Answer: (b)
Q.40
Potential difference between centre and the surface of a sphere of radius R with uniform charge density σ with in it will be
0%
a) σR2 /6εo
0%
b) σR2 /4εo
0%
c)zero
0%
d)σR2 /2εo
Explanation
Answer: (c)
Q.41
Two parallel plates of infinite dimensions are uniformly charged. The surface charge density on one is σA while on the other is σB field intensity at point C will be
0%
a) proportional to (σA - σB)
0%
b) proportional to (σA + σB)
0%
c)zero
0%
d)non-zero
Explanation
Answer:(b)
Q.42
Two charged metal plates each of area (A) carry charge +q and -q and face each other, the plates are separated by a small distance (d) the electric field between plates would be
0%
a) 2q/εoA
0%
b) 2qA/εoA
0%
c) q/εoA
0%
d) A/qεo
Explanation
Answer: (c)
Q.43
An electron is situated 3×10-9 m from one α-particle and 4×10-9m from another α particle. The magnitude of force on electron, when two α particles are 5 ×10-9 m apart is
0%
a)5.64×10-11 N
0%
b) 56.4×10-11 N
0%
c)0.564×10-11N
0%
d)564×10-11 N
Explanation
locations of all particle must be as show in figureFind magnitude of force between the electron and alpha particle. Then calculate resultant forceAnswer: (a)
Q.44
Two conducing spheres of radius a and b are equally charged. The ratio of their potential is
0%
a) a2 / b2
0%
b) b2 / a2
0%
c)a/b
0%
d)b/a
Explanation
Answer: (d)
Q.45
Two similar rings P and Q ( radius 0.1 m ) are placed co-axially at a distance 0.5 m apart. The charge on P and Q is 2µC and 4µC respectively. Work done due to moving of a 5µC charge from Centre of P to the Centre of Q is
0%
a) 1.28J
0%
b)0.72J
0%
c)0.144J
0%
d)1.44J
Explanation
Calculate potential at P=potential due to ring P at its centre + potential at P due to ring Q (take PQ as distance ) Calculate potential at Q=potential due to ring Q at its centre + potential at Q due to ring P (take PQ as distance ) Then calculate=(potential difference between P and Q) ×charge 5µC Answer:(b)
Q.46
Three point charges -q, +Q, -q are placed along a straight line at equal distances ( say r meter) Electric potential energy of the system of charges will be
0%
a) -3Kq2 / r
0%
b) -8Kq2 / r
0%
c) -3Kq2 / 2r
0%
d) -Kq2 / 2r
Explanation
Answer: (c)
Q.47
Four equal charges q are placed at corners of a square of side a. Potential energy of the whole system is
0%
a)4Kq2 / a
0%
b)
0%
c)
0%
d)
Explanation
Answer: (b)
Q.48
n small drops of the same size are charged to V voltage each. If they collapse to form a single large drop, then its potential will be
0%
a) V/n
0%
b) Vn
0%
c)Vn1/3
0%
d)Vn2/3
Explanation
Answer: (d)
Q.49
For the equilibrium of a charged bubble of surface tension T and radius r, the charge on the bubble should be
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
If the charged bubble is in equilibrium then pressure inside the bubble is equal to pressure out side the bubble When bubble is charged the bubble experience a outward electric force , this pressure is σ2 / 2εo Answer:(a)
Q.50
An electric dipole when placed in uniform electric field E will have minimum potential energy. If the positive direction of dipole moment makes an angle with E is
0%
a) π
0%
b) π/2
0%
c) zero
0%
d) 3π/2
Explanation
Answer: (c)
0 h : 0 m : 1 s
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Report Question
×
What's an issue?
Question is wrong
Answer is wrong
Other Reason
Want to elaborate a bit more? (optional)
Support mcqgeeks.com by disabling your adblocker.
×
Please disable the adBlock and continue.
Thank you.
Reload page