Physics - Electrostatics
Exam Duration: 45 Mins Total Questions : 30
A charge +q located at O is placed midway between two charges of +q each.All the three charges lie on a straight line. The charge at O
- (a)
will be in unstable equilibrium
- (b)
will be in stable equilibrium
- (c)
will not be in stable equilibrium
- (d)
will move laterally along the right bisector of the line
A wimshurst machine cannot work in vacuum because
- (a)
there is no air
- (b)
air is a bad conductor of electricity
- (c)
there is no mutual collision of molecules
- (d)
there is optimum pressure of air required for its operation
- (e)
Charge is produced by conduction
The edge effect in a parallel plate capacitor can be made negligibly small if
- (a)
the separation between the two plates is small
- (b)
the separation is small and area of the plates is large
- (c)
the area of the plates is large
- (d)
the separation is large and area is small
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
The dimensional formula for electric field strength is
- (a)
\(ML{ T }^{ -2 }{ I }^{ -1 }\)
- (b)
\(ML ^ { -1 }{ T }^{ -3 }{ I }^{ -1 }\)
- (c)
\(ML{ T }^{ -2 }{ I }\)
- (d)
\(ML{ T }^{ -3 }{ I }^{ -1 }\)
A parallel plate capacitor stores its electrical energy in
- (a)
the plate at higher potential
- (b)
the plate at lower potential
- (c)
the potential difference between the two plates
- (d)
the electric field between the two plates
The dimensional formula for electric potential is
- (a)
\(M { L }^{2}{ T }^{ -3 }{ I }^{ -1 }\)
- (b)
\(M { L }^{2}{ T }^{ -3 }{ I }\)
- (c)
\(M { L }^{2}{ T }^{ -2 }{ I }^{ -1 }\)
- (d)
\(M { L }^{2}{ T }^{ -2 }{ I }\)
A particle with mass m and carrying charge +q is located midway between two fixed particles that carry equal charges +q and are separated by a distance 2l.The middle charge is slightly displaced along the line joining the fixed charges and it is restricted to move along the line joining the fixed charges.the angular frequency of the middle charge is given by
- (a)
\({ \omega }^{ 2 }=\frac { { q }^{ 2 } }{ 4\pi { \epsilon }_{ 0 }m{ l }^{ 3 } } \)
- (b)
\({ \omega }^{ 2 }=\frac { { q }^{ 2 } }{ 2\pi { \epsilon }_{ 0 }m{ l }^{ 3 } } \)
- (c)
\({ \omega }^{ 2 }=\frac { { 2q }^{ 2 } }{ \pi { \epsilon }_{ 0 }m{ l }^{ 3 } } \)
- (d)
\({ \omega }^{ 2 }=\frac { { q }^{ 2 } }{ \pi { \epsilon }_{ 0 }m{ l }^{ 3 } } \)
Figure shows a charge +Q at a distance 2d froma charge -Q and a point P at a distance d from -Q.The field strength at p is
- (a)
\(\frac { Q }{ 4\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along BP
- (b)
\(\frac { Q }{ 36\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along PA
- (c)
\(\frac { 5Q }{ 18\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along BP
- (d)
\(\frac { 2Q }{ 9\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along PB
A battery is permanently connected to a parallel-plate capacitor P and the energy stored in P is E joules.When one plate is moved so that the separation of the plates os doubled, the energy now stored in joules is
- (a)
E
- (b)
2E
- (c)
E/2
- (d)
4E
The times of electric force produced by a positive charge +3Q in combination with a negative charge -Q is best shown 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
Equal charges are given to two conducting spheres of different radii.the potential will
- (a)
be more on the smaller sphere
- (b)
be more on the bigger sphere
- (c)
be equal to the both the sphere
- (d)
depends on the nature of the material of the sphere
A capacitor of capacity 2\(\mu F\)is charged to a potential difference of 12 V.it is then connected across an inductance of 0.6mH.the current in amperes across the capacitor is 6V is
- (a)
0.6
- (b)
1.2
- (c)
2.4
- (d)
3.6
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
Five balls numbered 1 to 5 are suspended using separate threads. Pairs (1,2), (2,4) and (4,1) shows electrostatic attraction, while pairs (2,3) and (4,5) shows repulsion. Therefore, ball 1 must be,
- (a)
positively charged
- (b)
negatively charged
- (c)
neutral
- (d)
None of the above
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