133 + Interview Questions in ELECTROSTATIC-POTENTIAL IN GENERAL AWARENESS Page 3 InterviewSolution

101.	If the circumference of a sphere is 2 m, then capacitance of sphere in water would beA. 2700 pFB. 2760 pFC. 2780 pFD. 2800 pF
Answer» Correct Answer - D

Discussion

102.	Two capacitors of `10 pF` and `20 pF` are connected to 200 V and 100 V sources, respectively. If they are connected by the wire, then what is the common potential of the capacitors?A. 133.3 VB. 150 VC. 300 VD. 400 V
Answer» Correct Answer - A

Discussion

103.	An isolated sphere has a capacitance of 50 pF. (a) Calculate its radius. (b) how much charge should be placed on it to raise its potential ot `10^4 V`?A. 90 cmB. 45 cmC. 11.50 cmD. 5.75 cm
Answer» Correct Answer - B

Discussion

104.	Three capacitors each of capacitance `C` and of breakdown voltage `V` are joined in series. The capacitance and breakdown voltage of the combination will beA. `(C)/(3),(V)/(3)`B. `3C,(V)/(3)`C. `(C)/(3),3V`D. `3C,3V`
Answer» Correct Answer - C

Discussion

105.	An electric dipole when placed in a uniform electric field `E` will have minimum potential energy, if the positive direction of dipole moment makes the following angle with `E`A. zeroB. `(pi)/(2)`C. `pi`D. `(3pi)/(2)`
Answer» Correct Answer - A

Discussion

106.	A molecule with a dipole moment `p` is placed in an electric field of strength `E`. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency isA. `-2pE`B. `-pE`C. `pE`D. 2pE
Answer» Correct Answer - D

Discussion

107.	The energy stored in the condenser isA. kinetic energyB. potential energyC. elastic energyD. magnetic energy
Answer» Correct Answer - B

Discussion

108.	The force between the plates of a parallel plate capacitor of capacitance `C` and distance of separation of the plates `d` with a potential difference `V` between the plates, is.A. `(CV^(2))/(2d)`B. `(C^(2)V^(2))/(2d^(2))`C. `(C^(2)V^(2))/(d^(2))`D. `(V^(2)d)/(C)`
Answer» Correct Answer - A

Discussion

109.	The capacity and the energy stored in a parallel plate condenser with air between its plates are respectively `C_(0)` and `W_(0)`. If the air is replaced by glass (dielectric constant `= 5`) between the plates, the capacity of the plates and the energy stored in it will respectively beA. `5C_(0),5W_(0)`B. `5C_(0),(W_(0))/(5)`C. `(C_(0))/(5),5W_(0)`D. `(C_(0))/(5),(W_(0))/(5)`
Answer» Correct Answer - C

Discussion

110.	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 beA. `(1)/(3)V`B. `(2)/(3)V`C. `(3)/(2)V`D. 3V
Answer» Correct Answer - B

Discussion

111.	The capacitance of the earth, viewed as a spherical conductor of radius 6408 km isA. `980 mu F`B. `1424 muF`C. `712 muF`D. `356 muF`
Answer» Correct Answer - C

Discussion

112.	The capacity of a spherical conductor isA. `(R)/(4 pi epsilon_(0))`B. `(4 pi epsilon_(0))/(R)`C. `4 pi epsilon_(0)R`D. `4 pi epsilon_(0)R^(2)`
Answer» Correct Answer - C

Discussion

113.	The potentials of the two plates of capacitor are `+10V` and `-10 V`. The charge on one of the plate is `40 C`. The capacitance of the capacitor isA. 2 FB. 4 FC. 0.5 FD. 0.25 F
Answer» Correct Answer - A

Discussion

114.	Three plates `A, B, C` each of area `50 cm^(2)` have separation `3 mm` between `A` and `B mm` between `B` and `C`. The energy stored when the plates area fully charged is A. `1.6xx10^(-9) J`B. `2.1 xx10^(-9) J`C. `5xx10^(-9) J`D. `7xx10^(-9) J`
Answer» Correct Answer - B

Discussion

115.	If a charged spherical conductor of radius 5 cm has potential V at a point distant 5 cm its centre, then the potential at a point distant 30 cm from the centre will beA. `(1)/(3)V`B. `(1)/(6)V`C. `(3)/(2)V`D. `3 V`
Answer» Correct Answer - B

Discussion

116.	Two plates are at potentials `-10 V` and `+30 V`. If the separation between the plates be `2 cm`. The electric filed between them isA. 2000 V/mB. 1000 V/mC. 500 V/mD. 3000 V/m
Answer» Correct Answer - A

Discussion

117.	The electrostatic potential on the surface of a charged concducting sphere is `100 V`. Two statements are made in this regard `S_(1) :` at any inside the sphere, electric intensity is zero. `S_(2) :` at any point inside the sphere, the electrostatic potential is `100 V`.A. `S_(1)` is true but `S_(2)` is falseB. Both `S_(1) and S_(2)` are falseC. `S_(1)` is true `S_(2)` is also true and `S_(1)` is the cause of `S_(2)`D. `S_(1)` is true, `S_(1) is also true but the statements are independent
Answer» Correct Answer - C

Discussion

118.	Three charges `Q, (+q)` and `(+q)` are placed at the vertices of an equilateral triangle of side `l` as shown in the figure. It the net electrostatic energy of the system is zero, then `Q` is equal to A. `(-(q)/(2))`B. `(-q)`C. `(+q)`D. zero
Answer» Correct Answer - A

Discussion

119.	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 A. `(-q)/(1+sqrt(2))`B. `(-2q)/(2+sqrt(2))`C. `-2q`D. `+q`
Answer» Correct Answer - B

Discussion

120.	Assertion : For a non-uniformly charged thin circular ring with net charge zero, the electric field at any point on axis of the ring is zero. Reason : For a non-uniformly charged thin circular ring with net charge zero, the electric potential at each point on axis of the ring is zero.A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.B. If both Assertion and Reason are true but Reason is not correct explanation of Assertion.C. If Assertion is true but Reason is false.D. If Assertion is false but Reason is true.
Answer» Correct Answer - D

Discussion

121.	A charge +Q is uniformly distributed over a thin ring of the radius R. The velocity of an electron at the moment when it passes through the centre O of the ring, if the electron was initially at far away on the axis of the ring is (m=mass of electron, `K=1/(4pi epsi_(0))`)A. `sqrt(((2KQe)/(mR)))`B. `sqrt(((Kqe)/m))`C. `sqrt(((Kme)/(QR)))`D. `sqrt(((Kqe)/(mR)))`
Answer» Correct Answer - A

Discussion

122.	The ionisation potential of mercury is 10.39 V. How far an electron must travel in an electric field of `1.5 xx 10^(6) V//m` to gain sufficient energy to ionise mercury ?A. `(10.39)/(1.6xx10^(-19))` mB. `(10.39)/(2xx1.6xx10^(-19))` mC. `10.39 xx 1.6 xx 10^(-19)` mD. `(10.39)/(1.5xx10^(6))` m
Answer» Correct Answer - D E=dV/dx ......................................eq 1 here E=1.5 x \(10^6\) V/m dV=10.39 V we have to find dx so substituing in eq 1,we get 1.5 x\(10^6\) = 10.39/dx dx=10.39/1.5 x \(10^6\) m so the answer is option d

122.

The ionisation potential of mercury is 10.39 V. How far an electron must travel in an electric field of `1.5 xx 10^(6) V//m` to gain sufficient energy to ionise mercury ?A. `(10.39)/(1.6xx10^(-19))` mB. `(10.39)/(2xx1.6xx10^(-19))` mC. `10.39 xx 1.6 xx 10^(-19)` mD. `(10.39)/(1.5xx10^(6))` m

Answer» Correct Answer - D

E=dV/dx ......................................eq 1

here E=1.5 x \(10^6\) V/m

dV=10.39 V

we have to find dx

so substituing in eq 1,we get

1.5 x\(10^6\) = 10.39/dx

dx=10.39/1.5 x \(10^6\) m

so the answer is option d

Discussion

123.	Three condensers each of capacitance 2F are put in series. The resultant capacitance isA. 6 FB. `(3)/(2)F`C. `(2)/(3)F`D. 5 F
Answer» Correct Answer - C

Discussion

124.	A spherical shell of radius 10 cm is carrying a charge q. If the electric potential at distances 5 cm, 10 cm and 15 cm from the centre of the spherical shell is `V_(1), V_(2)` and `V_(3)` respectively, thenA. `V_(1)=V_(2) gt V_(3)`B. `V_(1) gt V_(2) gt V_(3)`C. `V_(1)=V_(2) lt V_(3)`D. `V_(1) lt V_(2) lt V_(3)`
Answer» Correct Answer - A

Discussion

125.	Two condensers `C_(1)` and `C_(2)` in a circuit are jhioned as shown in . The potential fo point `A` is ` V_1` and that of `B` is ` V_2` . The potential of point `D` will be ` A. `(1)/(2)(V_(1)+V_(2))`B. `(C_(2)V_(1)+C_(1)V_(2))/(C_(1)+C_(2))`C. `(C_(1)V_(1)+C_(2)V_(2))/(C_(1)+C_(2))`D. `(C_(2)V_(1)-C_(1)V_(2))/(C_(1)+C_(2))`
Answer» Correct Answer - C

Discussion

126.	Two condensers, one of capacity `C` and the other of capacity `C//2` are connected to a `V` volt battery, as shown. The work done in charging fully both the condensers isA. `2CV^(2)`B. `1//4CV^(2)`C. `3//4CV^(2)`D. `(1)/(2)CV^(2)`
Answer» Correct Answer - C

Discussion

127.	Two condensers of capacity `0.3 muF` and `0.6muF` respectively are connected in series. The combination is connected across a potential of `6` volts. The ratio of energies stored by the condensers will beA. `(1)/(2)`B. 2C. `(1)/(4)`D. 4
Answer» Correct Answer - B

Discussion

128.	In the circuit shown here `C_(1) = 6muF, C2 = 3muF` and battery `B = 20V`. The Switch `S_(1)` is first closed. It is then opened and afterwards `S_(2)` is closed. What is the charge finally on `C_(2)` A. `120 muC`B. `80 muC`C. `40 muC`D. `20 muC`
Answer» Correct Answer - C

Discussion

129.	A capacitor of capacity C hasd charge Q and stored energy is W. if the charge is increased to 2Q, then the stored energy will beA. 2WB. W/2C. 4WD. W/4
Answer» Correct Answer - C

Discussion

130.	An infinite number of identical capacitors each of capacitance `1 mF` are connected as shown in the figure. Then the equivalent capacitance between `A` and `B` is. .A. `1 muF`B. `2 muF`C. `1/2 muF`D. `oo`
Answer» Correct Answer - B

Discussion

131.	Three identical metallic uncharged spheres A, B and C of radius a are kept on the corners of an equilateral triangle of side `d (d gt gt a)`. A fourth sphere (radius a) which has charge Q touches A and is then removed to a position for away. B is earthed and then the earth connection is removed. c is then earthed. The charge on C isA. `(Qa)/(2d) ((2d-a)/(2d))`B. `(Qa)/(2d) ((2d-a)/(d))`C. `(Qa)/(2d) ((a-d)/d)`D. `(2Qa)/(d) ((d-a)/(2d))`
Answer» Correct Answer - C

Discussion

132.	The ratio of moment of an electron and an `alpha`-particle which are accelerated from rest by a potential difference of `100V` isA. 1B. `sqrt((2m_(e))/(m_(alpha)))`C. `sqrt((m_(e))/(m_(alpha)))`D. `sqrt((m_(e))/(2m_(alpha)))`
Answer» Correct Answer - D

Discussion

133.	A capacity of capacity `C_(1)` is charged up to `V` volt and then connected to an uncharged capacitor of capacity `C_(2)`. Then final potential difference across each will beA. `(C_(2))/(C_(1)+C_(2))V_(0)`B. `(C_(1))/(C_(1)+C_(2))V_(0)`C. `(C_(1)+C_(2))/(C_(2))`D. `(C_(1)+C_(2))/(C_(1))V_(0)`
Answer» Correct Answer - B

Discussion

Explore topic-wise InterviewSolutions in .

If the circumference of a sphere is 2 m, then capacitance of sphere in water would beA. 2700 pFB. 2760 pFC. 2780 pFD. 2800 pF

Two capacitors of `10 pF` and `20 pF` are connected to 200 V and 100 V sources, respectively. If they are connected by the wire, then what is the common potential of the capacitors?A. 133.3 VB. 150 VC. 300 VD. 400 V

An isolated sphere has a capacitance of 50 pF. (a) Calculate its radius. (b) how much charge should be placed on it to raise its potential ot `10^4 V`?A. 90 cmB. 45 cmC. 11.50 cmD. 5.75 cm

Three capacitors each of capacitance `C` and of breakdown voltage `V` are joined in series. The capacitance and breakdown voltage of the combination will beA. `(C)/(3),(V)/(3)`B. `3C,(V)/(3)`C. `(C)/(3),3V`D. `3C,3V`

An electric dipole when placed in a uniform electric field `E` will have minimum potential energy, if the positive direction of dipole moment makes the following angle with `E`A. zeroB. `(pi)/(2)`C. `pi`D. `(3pi)/(2)`

A molecule with a dipole moment `p` is placed in an electric field of strength `E`. Initially the dipole is aligned parallel to the field. If the dipole is to be rotated to be anti-parallel to the field, the work required to be done by an external agency isA. `-2pE`B. `-pE`C. `pE`D. 2pE

The energy stored in the condenser isA. kinetic energyB. potential energyC. elastic energyD. magnetic energy

The force between the plates of a parallel plate capacitor of capacitance `C` and distance of separation of the plates `d` with a potential difference `V` between the plates, is.A. `(CV^(2))/(2d)`B. `(C^(2)V^(2))/(2d^(2))`C. `(C^(2)V^(2))/(d^(2))`D. `(V^(2)d)/(C)`

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 beA. `(1)/(3)V`B. `(2)/(3)V`C. `(3)/(2)V`D. 3V

The capacitance of the earth, viewed as a spherical conductor of radius 6408 km isA. `980 mu F`B. `1424 muF`C. `712 muF`D. `356 muF`

The capacity of a spherical conductor isA. `(R)/(4 pi epsilon_(0))`B. `(4 pi epsilon_(0))/(R)`C. `4 pi epsilon_(0)R`D. `4 pi epsilon_(0)R^(2)`

The potentials of the two plates of capacitor are `+10V` and `-10 V`. The charge on one of the plate is `40 C`. The capacitance of the capacitor isA. 2 FB. 4 FC. 0.5 FD. 0.25 F

Three plates `A, B, C` each of area `50 cm^(2)` have separation `3 mm` between `A` and `B mm` between `B` and `C`. The energy stored when the plates area fully charged is A. `1.6xx10^(-9) J`B. `2.1 xx10^(-9) J`C. `5xx10^(-9) J`D. `7xx10^(-9) J`

If a charged spherical conductor of radius 5 cm has potential V at a point distant 5 cm its centre, then the potential at a point distant 30 cm from the centre will beA. `(1)/(3)V`B. `(1)/(6)V`C. `(3)/(2)V`D. `3 V`

Two plates are at potentials `-10 V` and `+30 V`. If the separation between the plates be `2 cm`. The electric filed between them isA. 2000 V/mB. 1000 V/mC. 500 V/mD. 3000 V/m

Three charges `Q, (+q)` and `(+q)` are placed at the vertices of an equilateral triangle of side `l` as shown in the figure. It the net electrostatic energy of the system is zero, then `Q` is equal to A. `(-(q)/(2))`B. `(-q)`C. `(+q)`D. zero

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 A. `(-q)/(1+sqrt(2))`B. `(-2q)/(2+sqrt(2))`C. `-2q`D. `+q`

The ionisation potential of mercury is 10.39 V. How far an electron must travel in an electric field of `1.5 xx 10^(6) V//m` to gain sufficient energy to ionise mercury ?A. `(10.39)/(1.6xx10^(-19))` mB. `(10.39)/(2xx1.6xx10^(-19))` mC. `10.39 xx 1.6 xx 10^(-19)` mD. `(10.39)/(1.5xx10^(6))` m

Three condensers each of capacitance 2F are put in series. The resultant capacitance isA. 6 FB. `(3)/(2)F`C. `(2)/(3)F`D. 5 F

Two condensers, one of capacity `C` and the other of capacity `C//2` are connected to a `V` volt battery, as shown. The work done in charging fully both the condensers isA. `2CV^(2)`B. `1//4CV^(2)`C. `3//4CV^(2)`D. `(1)/(2)CV^(2)`

Two condensers of capacity `0.3 muF` and `0.6muF` respectively are connected in series. The combination is connected across a potential of `6` volts. The ratio of energies stored by the condensers will beA. `(1)/(2)`B. 2C. `(1)/(4)`D. 4

In the circuit shown here `C_(1) = 6muF, C2 = 3muF` and battery `B = 20V`. The Switch `S_(1)` is first closed. It is then opened and afterwards `S_(2)` is closed. What is the charge finally on `C_(2)` A. `120 muC`B. `80 muC`C. `40 muC`D. `20 muC`

A capacitor of capacity C hasd charge Q and stored energy is W. if the charge is increased to 2Q, then the stored energy will beA. 2WB. W/2C. 4WD. W/4

An infinite number of identical capacitors each of capacitance `1 mF` are connected as shown in the figure. Then the equivalent capacitance between `A` and `B` is. .A. `1 muF`B. `2 muF`C. `1/2 muF`D. `oo`

The ratio of moment of an electron and an `alpha`-particle which are accelerated from rest by a potential difference of `100V` isA. 1B. `sqrt((2m_(e))/(m_(alpha)))`C. `sqrt((m_(e))/(m_(alpha)))`D. `sqrt((m_(e))/(2m_(alpha)))`

A capacity of capacity `C_(1)` is charged up to `V` volt and then connected to an uncharged capacitor of capacity `C_(2)`. Then final potential difference across each will beA. `(C_(2))/(C_(1)+C_(2))V_(0)`B. `(C_(1))/(C_(1)+C_(2))V_(0)`C. `(C_(1)+C_(2))/(C_(2))`D. `(C_(1)+C_(2))/(C_(1))V_(0)`