A hollow metal sphere of radius 5 cm is charged so that the potential on its surface is 10 V. The potential at the centre of the sphere is -
0 V
10 V
Same as at point 5 cm away from the surface
Same as at point 25 cm away from the surface
If a unit positive charge is taken from one point to another over an equipotential surface, then -
Work is done on the charge
Work is done by the charge
Work done is constant
No work is done
In the electric field of a point charge q, a certain charge is carried from point A to B, C, D and E. Then the work done
Is least along the path AB
Is least along the path AD
Is zero along all the paths AB, AC, AD and AE
Is least along AE
A conductor with a positive charge:
is always at +ve potential.
is always at zero potential.
is always at a negative potential.
may be at +ve, zero or –ve potential.
On rotating a point charge having a charge q around a charge Q in a circle of radius r, the work done will be:
q×2πr
q×2πQr
Zero
Q2ε0r
Two charge +q and –q are situated at a certain distance. At the point exactly midway between them -
Electric field and potential both are zero
Electric field is zero but the potential is not zero
Electric field is not zero but the potential is zero
Neither electric field nor potential is zero
In the figure the charge Q is at the centre of the circle. Work done by the conservative force is maximum when another charge is taken from point P to:
K
L
M
N
Two insulated charged conducting spheres of radii 20 cm and 15 cm respectively and having an equal charge of 10 C are connected by a copper wire and then they are separated. Then -
Both the spheres will have the same charge of 10 C
Surface charge density on the 20 cm sphere will be greater than that on the 15 cm sphere
Surface charge density on the 15 cm sphere will be greater than that on the 20 cm sphere
Surface charge density on the two spheres will be equal
Two equal charges q are placed at a distance of 2a and a third charge –2q is placed at the midpoint. The potential energy of the system is -
q28πε0a
6q28πε0a
−7q28πε0a
9q28πε0a
A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The kinetic energy attained by the particle after moving a distance y is -
qEy2
qE2y
qEy
q2Ey
How much kinetic energy will be gained by an α– particle in going from a point at 70 V to another point at 50 V ?
40 eV
40 keV
40MeV
0 eV
If a charged spherical conductor of radius 10 cm has potential V at a point distant 5 cm from its centre, then the potential at a point distant 15 cm from the centre will be -
13V
23V
32V
3 V
What is the potential energy of two equal positive point charges of 1 μC each held 1 m apart in air ?
9×10−3J
9×10−3eV
2eV/m
An oil drop having charge 2e is kept stationary between two parallel horizontal plates 2.0 cm apart when a potential difference of 12000 volts is applied between them. If the density of oil is 900 kg/m3, the radius of the drop will be -
2.0×10−6m
1.7×10−6m
1.4×10−6m
1.1×10−6m
The ratio of momenta of an electron and an α-particle which are accelerated from rest by a potential difference of 100 volt is
1
2memα
memα
me2mα
When a proton is accelerated through 1V, then its kinetic energy will be -
1840 eV
13.6 eV
1 eV
0.54 eV
Ten electrons are equally spaced and fixed around a circle of radius R. Relative to V = 0 at infinity, the electrostatic potential V and the electric field E at the centre C are
V≠0 and E→≠0
V≠0 and E→=0
V = 0 and E→=0
V = 0 and E→≠0
The displacement of a charge Q in the electric field E=e1i^+e2j^+e3k^ is r^=ai^+bj^. The work done is
Q(ae1+be2)
Q(ae1)2+(be2)2
Q(e1+e2)a2+b2
Q(e12+e22) (a+b)
Three charges Q, +q and +q are placed at the vertices of a right-angled isosceles triangle as shown. The net electrostatic energy of the configuration is zero if Q is equal to
−q1+2
−2q2+2
–2q
+q
A cube of a metal is given a positive charge Q. For the above system, which of the following statements is true ?
Electric potential at the surface of the cube is zero
Electric potential within the cube is zero
Electric field is normal to the surface of the cube
Electric field varies within the cube
Three charges Q, (+q) and (+q) are placed at the vertices of an equilateral triangle of side l as shown in the figure. If the net electrostatic energy of the system is zero, then Q is equal to:
−q2
(–q)
(+q)
Electric potential at any point is V=−5x+3y+15z, then the magnitude of the electric field is
32
42
52
7
Kinetic energy of an electron accelerated in a potential difference of 100 V is
(1) 6 × 10–17 J
(2) 1.6 × 1021 J
(3) 1.6 × 10–29 J
(4) 1.6 × 10–34 J
If identical charges (–q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q) which is placed at centre of the cube will be -
82q24πε0b
−82q2πε0b
−42q2πε0b
−4q23πε0b
A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 kV, its kinetic energy will be -
1840 keV
1/1840 keV
1 keV
920 keV
To form a composite 16 μF, 1000 V capacitor from a supply of identical capacitors marked 8 μF, 250 V, we require a minimum number of capacitors
40
8
2
A charge of 10 e.s.u. is placed at a distance of 2 cm from a charge of 40 e.s.u. and 4 cm from another charge of 20 e.s.u. The potential energy of the charge 10 e.s.u. is (in ergs)
87.5
112.5
150
250
When one electron is taken towards the other electron, then the electric potential energy of the system -
Decreases
Increases
Remains unchanged
Becomes zero
Four charges +Q, −Q, +Q, −Q are placed at the corners of a square taken in order. At the centre of the square
E=0, V=0
E=0, V≠0
E≠0, V=0
Point charge q1 = 2 μC and q2 = –1 μC are kept at points x = 0 and x = 6 respectively. Electrical potential will be zero at points
x = 2 and x = 9
x = 1 and x = 5
x = 4 and x = 12
x = –2 and x = 2
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