Physics - Electrostatistics
Exam Duration: 45 Mins Total Questions : 30
Electric potential difference is defined as the
- (a)
Scalar function of position
- (b)
single-valued scalar function of two positions
- (c)
potential energy of a system of charges
- (d)
potential associated with the electric field
A parallel plate capacitor has charge +Q and -Q on its plate.The separation between the plates is doubled
- (a)
charge on the plates is reduced to half
- (b)
capacitance is doubled
- (c)
Potential difference between the plates is doubled
- (d)
Electric field between the plates is reduced to half
Three identical small balls, each of mass m=2g, are suspended from a fixed point by three non-conducting threads, each with a length of 50 cm and negligible mass. At equilibrium the three balls form an equilateral triangle with sides of 30 cm.the common charge q that is carried by each ball is
- (a)
0.204\(\mu C\)
- (b)
\(0.20\mu C\)
- (c)
\(0.408\mu C\)
- (d)
\(0.306\mu C\)
If mass of electron \({ m }_{ e }=9.11\times { 10 }^{ -31 }\)kg and charge on electron,e=\({ m }_{ e }=1.60\times { 10 }^{ -19 }\)C, then the ratio of electrostatic(\({ F } _ { e }\))and gravitational(\({ F } _ { g }\)) forces that act between two stationary electrons is of the order of
- (a)
\({ 10 } ^ { 12 }\)
- (b)
\({ 10 } ^ { 22 }\)
- (c)
\({ 10 } ^ { 32 }\)
- (d)
\({ 10 } ^ { 42 }\)
Figure shows a charge +Q at a distance 2d away from a charge -Q and a point P at a distance d from -Q.The total potential at P due to the charges +q and -Q, using S.I.units is
- (a)
\(\frac { -2Q }{ 9\pi { \epsilon }_{ 0 }{ d }} \)
- (b)
\(\frac { -Q }{ 6\pi { \epsilon }_{ 0 }{ d }} \)
- (c)
\(\frac { +3Q }{ 4\pi { \epsilon }_{ 0 }{ d }} \)
- (d)
\(\frac { +Q }{ 6\pi { \epsilon }_{ 0 }{ d }} \)
A capacitor of capacitance C is fully charged by a 200V battery.It is then discharged through thermally insulated block of specific heat capacity \(2.5\times { 10 }^{ 2 }Jk{ g }^{ -1 }{ K }^{ -1 }\) and of mass 0.1 kg.If the temperature of the block rises by 0.4 K, the value of C is
- (a)
50 mF
- (b)
0.5 mF
- (c)
2 mF
- (d)
0.2 mF
Consider the lines of force to illustrate the electric field produced by a positive charge +3Q in combination with a negative charges -Q.If \({E} _ { + }\) is the electric field due to +3Q and E that due to -Q at a common point p, then they are best shown by which figure
- (a)
- (b)
- (c)
- (d)
For a uniformly charged sphere having a total of charge +Q and radius R,the electric field strength E(r) at distance r from the centre of the sphere is given by
- (a)
- (b)
- (c)
- (d)
All of the corners,except one, of a 1-m cube are occupied by charges of \(+1 \mu C\).The electric potential at the empty corner is \(K=\frac { 1 }{ 4\pi { \epsilon }_{ 0 } } =9\times { 10 }^{ 9 }Nm^{ 2 }.{ C }^{ -2 }\)]
- (a)
\(5.12\times { 10 }^{ 3 }V\)
- (b)
\(5.12\times { 10 }^{ 4 }V\)
- (c)
\(10.24\times { 10 }^{ 3 }V\)
- (d)
\(15.36\times { 10 }^{ 4 }V\)
A \(4\mu F\) capacitor is charged to a potential difference of 150V
- (a)
the amount of energy stored in the capacitor is \(4.5\times { 10 } ^ { -2 } J\)
- (b)
the amount of work that would have to be done by an extrenal agency to double the amount of charge on the capacitor is 0.135 J
- (c)
Choice (a) is correct but (b) is incorrect
- (d)
Both (a) and (b) are correct
The dielectric constant of metals is
- (a)
1
- (b)
greater than 1 but finite
- (c)
zero
- (d)
infinite
A parallel plate capacitor has a capacity C.The separation between the plates is doubled and a dielectric medium is introduced between the plates.If the capacity now becomes 2C, the dielectric constant of the medium is
- (a)
2
- (b)
1
- (c)
4
- (d)
8
Two equal point charges are fixed at x=-a and x=+a on the x-axis .Another point charge Q is placed at the orgin.The change in the electrical potential energy of Q,when it is displaced by a small distance x along the x-axis , is approximately proportional to
- (a)
x
- (b)
\({x} ^ { 2} \)
- (c)
\({x}^{3}\)
- (d)
1/x
Atmospherics
- (a)
are devices to measure atmospheric pressure
- (b)
are devices to measure height of atmosphere
- (c)
Comprise the scientific study of travel outside the Earth's atmosphere
- (d)
are electrical discharges which take place in the atmosphere
Two identical conductors of copper and aluminium are placed in an identical electric fields. The magnitude of induced charge in the aluminium will be
- (a)
zero
- (b)
greater than in copper
- (c)
equal to that in copper
- (d)
less that in copper
A parallel plate capacitor is made of two circular plates separated by a distance of 5 mm and with a dielectric of dielectric constant 2.2 between them. when the electric field in the dielectric is 3 x 104 V/m, the charge density of the positive plate will be close to
- (a)
6 x 10-7 C/m2
- (b)
3 x 10-7 C/m2
- (c)
3 x 104 C/m2
- (d)
6 x 104 C/m2
This question has Statement I and statement II. Of the four choices given after the statement choose the one that best describes the two statements.
An insulating solid sphere of radius R has a uniform positive charge density \(\rho\). As a result of this uniform charge distribution, there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere. The electric potential at infinity is zero.
Statement I When a charge q is taken from the centre to surface of the sphere its potential energy changes by, \(\frac{q\rho}{3\epsilon_0}\).
Statement II The electric field at a distance r(r
- (a)
Statement I is false, Statement II is true
- (b)
Statement I is true, Statement II is false
- (c)
Statement I is true, Statement II is true, Statement II is correct explanation for Statement II
- (d)
Statement I is true, Statement II is true, Statement II is not the correct explanation for Statement II
A circular ring carries a uniformly distributed positive charge and lies in XY-plane with the centre at origin of coordinate system. If at a point (0,0,Z) electric field is E, which of the following graphs is correct ?
- (a)
- (b)
- (c)
- (d)
In a uniformly charged sphere of total charge Q and radius R, the electric field E is plotted as a function of distance from the centre. The graph which would correspond to the above will be
- (a)
- (b)
- (c)
- (d)
Two points P and Q are maintained at the potentials of 10 V and - 4V, respectively. The work done in moving 100 electron from P to Q is
- (a)
- 19 X 10-17 J
- (b)
9.60 X 10-17 J
- (c)
- 2.24 X 10-16 J
- (d)
2.24 X 10-16 J