Q.1.
A positively charge oil droplet remains stationary in the electric field between two horizontal plates separated by a distance of 1cm. If the charge on the drop is 9.6×10-16 C and the mass of the droplet is 10-11g. The potential difference between the plates is
-
100%
a)2.0 V
-
0%
b) 3.1 V
-
0%
c)1.02 V
-
0%
d)10.2V
Q.2.
A spark passes in air when the potential gradient at the surface of a charged conductor is 3×106 V/m. What must be the radius of an isolated metal sphere which can be charged to a potential of 3×106 volt before sparking into surrounding air ?
-
0%
a) 1 m
-
100%
b) 0.5 m
-
0%
c)8.85 m
-
0%
d)0.89 m
Q.3.
A 50µF capacitor is charged from 200V supply. After disconnected from supply, it is immediately connected in parallel with 30µF capacitor. The potential difference across the combination is
-
0%
a) 125 V
-
100%
b) 150 V
-
0%
c)175 V
-
0%
d)200 V
Explanation
Q.4.
An electric line of force is in the y-z plane is given by the equation y2 + z2=A particle with unit positive charge, initially at rest at the point y=0, Z=2 in the y-z plane
-
0%
a) will not move at all
-
50%
b) will move along z=0
-
0%
c) will move along a circular line of force
-
50%
d) will move along the line y=2
Q.5.
The capacitance of capacitor does not depend on
-
0%
a)the shape of the plates
-
33%
b) the size of the plates
-
33%
c)the charges on the plates
-
33%
d)the separation between the plates
Q.6.
Two capacitor 2µF and 4µF are connected in series across 120V supply. The potential across the 2µF capacitor is
-
0%
a) 120 V
-
100%
b) 40 V
-
0%
c)80 V
-
0%
d)60 V
Q.7.
A and B are two thin concentric hollow conductors having radii a and b and charge q and Q respectively. Given that a > b and P is a point between the two spheres and distance of P from the common centre is ( b
-
0%
a) q+Q/r
-
100%
b) q/a + Q/r
-
0%
c) q/a + Q/b
-
0%
d)q/b + Q/a
Q.8.
A parallel plate capacitor hs plates each of area A at separation d. It is charged to a potential V and then disconnected from the battery. If a slab of dielectric constant K is now introduced to fill the capacitor, the work done in the process is
-
50%
a)
-
0%
b)
-
50%
c)
-
0%
d)
Explanation
Q.9.
The charge on the drop of water is 3×10-8C. If its surface potential is 500V, its radius must be equal to
-
0%
a)81 cm
-
0%
b) 54 cm
-
100%
c)27 cm
-
0%
d)108cm
Q.10.
An air filed parallel plate capacitor is to be constructed which can store 12µC of charge when operated at 1200V. The dielectric strength of air is 3×106 V/m. What is the minimum area of the plates of the capacitor?
-
0%
a) 1 m2
-
0%
b) 0.45 m2
-
0%
c)1.5 m2
-
100%
d)1.2 m2
Explanation
Q.11.
A unit charge is given a displacement r=αi + βj in an electric field which has components E1 and E2 along x and y axes respectively. then work done is
-
100%
a)α(E1 + E2)
-
0%
b) β(E1 + E2)
-
0%
c)αE2 + βE1
-
0%
d)α E1 + βE2
Explanation
Q.12.
A pendulum bob of mass 80mg, carrying a charge of 2×10-8 C is at rest in a horizontal uniform electric field of 20000 V/m. The tension in the thread of the pendulum and the angle makes with the vertical are
-
0%
a) 9×10-4 N, tan-1 (1/2)
-
100%
b) 9×10-4 N, tan-1 (2)
-
0%
c) 9×10-3 N, tan-1 (1.5)
-
0%
d) 8×10-3 N, tan-1 (1/2)
Explanation
Q.13.
A charged sphere A having a radius 2cm is brought into constant with an uncharged sphere B having a radius 3cm. After the sphere are disconnected, the energy of B is 0.4J. The charge on the sphere A before contact is
-
100%
a)5.4 ×10-6C
-
0%
b) 2.7 ×10-6C
-
0%
c)1.8 ×10-6C
-
0%
d)3.6 ×10-6C
Explanation
Q.14.
The distance between the plates of a charged parallel plate capacitor disconnected from the battery is d=5 cm and the intensity of the electric field E=300V/m. An uncharged metal bar 1cm thick is introduced into the capacitor parallel to its plates. The ratio of the potential difference between the plates of the capacitor before and after the bar is introduced is
-
100%
a) 1.8
-
0%
b) 1.65
-
0%
c)1.25
-
0%
d)1.5
Explanation
Q.15.
Two uniformly large plane sheets S1 and S2 having charge densities σ1 and σ2 ( σ1 > σ2) are placed at a distance d parallel to each other. A charge qo is moving along a line of length a (a < d) at an angle of 45° with the normal to SThe work done by the electric field is
-
0%
a)
-
0%
b)
-
100%
c)
-
0%
d)
Explanation
Q.16.
A particle of mass m and charge q starts moving from rest along a straight line in an electric field E=Eo - αx where α is positive constant and x is the distance from starting point. Find the distance traveled by the particle till the moment it comes to instantaneous rest
-
0%
a) 2Eo / α
-
100%
b) Eo / α
-
0%
c) Eoq/ m
-
0%
d) Eo / Q
Explanation
Q.17.
Point charges q, -q, 2Q and Q are placed in order at the corners A, B, C and D of a square of side 2b. If the field at the midpoint CD is zero, then q/Q is
-
0%
a)1
-
0%
b) 2
-
100%
c)2√2 / 5
-
0%
d)5√5 /2
Explanation
Q.18.
An infinite plane sheet of positive charge has surface charge density σ A metallic ball of mass m and charge +Q is attached to a thread and is tied to a point A on the sheet PQ. The angle θ made by the string with the plane sheet is
-
0%
a)zero
-
100%
b)
-
0%
c)
-
0%
d)
Q.19.
Four metallic plates, each with surface area of oneside A, are palced at distance d from each other. The plates are connected as shown in the adjoining figure. Then the capacitance of the system between a and b is
-
100%
a)
-
0%
b)
-
0%
c)
-
0%
d)
Explanation
Q.20.
A parallel plate capacitor of capacitance C is connected to a battery and is charged to a potential difference V. Another capacitor of capacitance 2C is similarly charged to potential difference 2V. The charging battery is now disconnected and the capacitor are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other. The final energy of the configuration is
-
0%
a)zero
-
100%
b) (3/2)CV2
-
0%
c)(25/6)CV2
-
0%
d)(9/2)CV2
Q.21.
Consider the situation shown in figure. The capacitor A has a charge q on it whereas B is uncharged. The charge appearing on the capacitor B a long time time after the switch is closed is
-
0%
a) zero
-
0%
b) q/2
-
100%
c) q
-
0%
d) 2q
Q.22.
In figure shown the electric lies of force emerging from charged body. IF the electric fields at A and B are EA and EB respectively. IF the distance between A and B is r then
-
0%
a)EA > EB
-
0%
b) EA < EB
-
100%
c)EA=EB
-
0%
d)EA=(EB) / r2
Q.23.
The enrgy U stored in the electric field produced by a metal sphere of radius R containing a charge Q is
-
0%
a) Q / 8εoR2
-
0%
b) Q2 / 8πεoR
-
100%
c)Q / 8πεoR
-
0%
d)Q2 / 8πεoR2
Explanation
Q.24.
An electric dipole consists of two opposite charge each of magnitude 1×10-6 C separated by a distance 2cm. The dipole is placed in electric field of 10×105 N/C. The maximum torque on the dipole is
-
0%
a) 0.2× 10-3 N-m
-
0%
b) 1.0×10-3 N-m
-
100%
c)2×10-3 N-m
-
0%
d)4×10-3 N-m
Q.25.
A charge 10-9C is located at the origin in free space and another charge Q at (2, 0, 0). If the X-componant of the electric field at (3, 1,1) is zero, calculate the value of Q
-
0%
a) -0.42 nC
-
0%
b) 0.72nC
-
100%
c) -0.92nC
-
0%
d) -0.72C
Explanation
Q.26.
In a parallel plate capacitor, the plate separation of 10mm is very small compared with the size of the plates. A potential difference of 5.0kV is maintained across the plates. The electric field intensity between the plates is
-
0%
a)500 V/m
-
0%
b) 2.5×105 V/m
-
100%
c)5×105 V/m
-
0%
d)2.5×1013 V/m
Q.27.
A point charge q is located at the centre O of a spherical uncharged conducting layer provided with a small orifice as shown in figure. The inside and outside radii of the layer are equal to a and b respectively. What amount of work has to be performed to transfer the charge q slowly from the point O to infinity through the orifice
-
100%
a)
-
0%
b)
-
0%
c)
-
0%
d)
Explanation
Q.28.
A particle of mass m with charge q > 0 and initial kinetic energy K is projected from infinity towards a heavy nucleus of charge Q assumed to have a fixed position. If the aim is perfect, how close to the centre of the nucleus is the particle when it comes instantaneously to rest?
-
0%
a)
-
100%
b)
-
0%
c)
-
0%
d)
Explanation
Q.29.
The flow of charge through switch S when it is closed is
-
0%
a) zero
-
0%
b) q/4
-
0%
c) 2q/3
-
100%
d) q/3
Q.30.
The equivalent capacitance between point A and B shown in figure will be...( each capacitor is of capacitance 3µF)
-
0%
a)9 µF
-
0%
b) 1µF
-
0%
c)4.5µF
-
100%
d)6µF
Q.31.
Point charge q moves from point P to point S along the path PQRS in uniform electric field E parallel to the positive direction of the x-axis. The coordinates of point P, Q, R and S are (a, b, 0) (2a, 0, 0), (a, -b, 0) and (0, 0, 0) respectively. The work done by the field in the above process is given by the expression
-
100%
a) qaE
-
0%
b) -qaE
-
0%
c)q(√(a2+b2)E
-
0%
d)3qE(√[a2b2)]
Q.32.
A uniform electric field of 400 V/m is directed at 45° above the x-axis as shown in the figure. The potential difference VA - VB is given given by
-
0%
a)0
-
100%
b)4V
-
0%
c)6.4V
-
0%
d)2.8V
Explanation
Q.33.
Which of the following statement regarding electrostatics is wrong
-
0%
a) Charge is quantized
-
0%
b) charge is conserved
-
0%
c) There is no field near an isolated charge at rest
-
100%
d) A stationary charge produces both electric and magnetic fields
Q.34.
The dielectric constant of water is
-
0%
a)1
-
0%
b) 40
-
0%
c)81
-
100%
d)0.3
Q.35.
A very long uniform charged thread oriented along the axis of a circle of radius R rests on its centre with one of the ends. The charge of the thread per unit length is equal to λ. Find the flux of electric field across the circular area due to charges on the thread
-
0%
a) R/2ε0
-
100%
b) λR/ε0
-
0%
c)λR/2ε0
-
0%
d)λR/ε02
Explanation
Q.36.
The potential V(x, y) of an electrostatic field E=2axyi +a(x2 -y2)j. Where a is constant
-
0%
a) Vo +(a/3)y3 - ayx2
-
0%
b) Vo -(a/3)y3 + ayx2
-
0%
c) Vo +(a/3)y3 + ayx2
-
100%
d) Vo -(a/3)y3 - ayx2
Explanation
Q.37.
A charge q is placed at O in the cavity in a spherical uncharged conductor. Point S is outside the conductor. If the charge is displaced from O towards S still remaining with in the cavity
-
0%
a)electric field at S will increase
-
0%
b) electric field at S will decrease
-
100%
c)electric field at S will first increase and then decrease
-
0%
d)electric field at S will not change
Q.38.
For the circuit shown, which of the following statement is true?
-
0%
a) With S1 closed, V1=15V, V2=20 V
-
100%
b) With S3 closed, V1=V2=25V
-
0%
c)With S1 and S2 closed V1=V2=0
-
0%
d)With S1 and S3 closedV1=30V, V2=20V
Q.39.
In the given circuit, with steady current, the potential drop across the capacitor C must be
-
100%
a) V
-
0%
b) V/2
-
0%
c)V/3
-
0%
d)2V/3
Q.40.
A capacitor of capacitance C1=1µF withstands a maximum voltage V1=6kV while another of capacitance C2=2µF withstands a maximum voltage V2=4kV. If they are connected in series, maximum voltage the system can withstand is
-
0%
a) 15kV
-
0%
b) 12kV
-
100%
c) 9kV
-
0%
d) 6kV
Explanation
Q.41.
A ball of radius R is uniformly charged with the volume density ρ. Find the flux of the electric field strength vector across the ball's section formed by the plane located at a distance ro < R from the centre of the ball
-
0%
a)
-
0%
b)
-
100%
c)
-
0%
d)
Explanation
Q.42.
Consider the arrangement of three plates X, Y, and Z each of area A with separation between successive plates being d. The energy stored when the plates are fully charged is
-
100%
a) εoAV2 / 2d
-
0%
b) εoAV2 / d
-
0%
c)2εoAV2 / d
-
0%
d)3εoAV2 / 2d
Q.43.
A parallel plate air capacitor is connected to battery. The charge, voltage, electric field and energy associated with this capacitor are given by Qo, Vo Eo and Uo respectively .A dielectric slab is now introduced to fill the capacitor with the battery connected. The corresponding quantities are now Q, V, E and U respectively. Then
-
0%
a)Q > Qo
-
0%
b) E > Eo
-
0%
c)Uo >U
-
100%
d)V > Vo
Q.44.
The air plate can sustain an electric field of 3×106 V/m without breakdown of its insulation. The maximum amount of electrostatic energy per unit volume of air that can be stored in a parallel plate air capacitor is nearly
-
0%
a) 20 J/m3
-
0%
b) 40 J/m3
-
0%
c) 60 J/m3
-
100%
d) 80 J/m3
Q.45.
A parallel plate capacitor is filled by a dielectric whose permitivity varies with applied voltage according to the equation εo=αV where α=1(Volt)-Another identical capacitor without dielectric charged to a voltage Vo=20 volt is connected in parallel to the first "non linear" uncharged capacitor. The final voltage across the capacitor is
-
0%
a)20 V
-
0%
b) 10 V
-
0%
c)5 V
-
100%
d)4 V
Explanation
Q.46.
Between the plates of a parallel plate capacitor there is a metallic plate whose thickness takes up 0.6 of the capacitor gap. When the plate is absent, the capacitor has a capacity C=20 nF. The capacitor is connected to a d.c voltage source V=100V. The metallic plate is slowly extracted from the gapThe mechanical work performed in the process of extraction is
-
0%
a) 0.35mJ
-
0%
b) 0.25mJ
-
0%
c)0.15mJ
-
100%
d)0.10mJ
Q.47.
The ratio of electric force to gravitational force acting between two electrons will be
-
0%
a) 1×1036
-
0%
b) 2 × 1039
-
0%
c) 6 × 1045
-
100%
d)4 × 1042
Q.48.
Initially the spheres A and B are at potentials VA and VB respectively. Now sphere B is earthed by closing the switch. The potential of A becomes
-
100%
a) 0
-
0%
b) VA
-
0%
c) VA - VB
-
0%
d) VB
Explanation
Q.49.
A capacitor C is charged to a potential V by battery. The emf of the battery is V. It is then disconnected from battery and again connected with its polarity reversed to the battery
-
0%
a) The work done done by the battery is CV2
-
0%
b) The total charge that passes through the battery is 2CV
-
100%
c)the initial energy of the capacitor is greater than the final energy of the capacitor
-
0%
d)All are correct
Q.50.
The effective capacitance of the network between A and B is
-
0%
a) 0.9 µF
-
100%
b) 4.0µF
-
0%
c)1.33µF
-
0%
d)1.84µF