1638 + Interview Questions in ELECTROSTATICS IN GENERAL AWARENESS Page 29 InterviewSolution

1401.	Two points charges are located on the x-axis, `q_1=-1muC` at `x=0 and q_2=+1muc` at `x=1m`. a. Find the work that must be done by an external force to bring a third point charge `q_3=+1muC` from infinity to `x=2m`. b. Find the total potential energy of the system of three charges.
Answer» Correct Answer - A::B::C::D a. The work that must be done on `q_3` by an external force is equal to the difference of of potential energy `U` when the charge is at `x=2m` and the potential energy when it is at infinity. `:. W=U_f-U_i` `=1/(4piepsilon_0) [(q_3q_2)/((r_32)_f)+(q_3q_1)/((r_31)_f)+(q_2q_1)/((r_21)_f)]-1/(4piepsilon_0)[(q_3q_2)/((r_31)_i)+(q_3q_1)/((r_31)_i)+(q_2q_1)/((r_21)_i)]` Here `(r_21)_i=(r_21)_f` and `(r_32)_i=(r_31)_i=oo` `:. W=1/(4piepsilon_0)[(q_3q_2)/((r_32)_f-(q_3q_1)/((r_31)_f)]` Substituting the values, we have `W=(9.0xx10^9)(10^-12)[((1)(1))/((1.0))+((1)(-1))/((2.0))]` `=4.5xx10^-3J` b. The total potential energy of the three charges in given by `U=1/(4piepsilon_0)((q_3q_2)/r_32+(q_3q_1)/r_31+(q_2q_1)/r_21)` `=(9.0xx10^9)[((1)(1))/((1.0))+((1)(-1))/(2.0))+((1)(-1))/((1.0))](10^-12)` `=-4.5xx10^-3J`

Discussion

1402.	For charges `q_1=1muC, q_2=2muC, q_3=-3muC` and `q_4=4muC` are kept on the vertices of a square of side `1m`. Find the electric potential energy of this system of charges.
Answer» Correct Answer - A::B In this problem `r_41=r_43=r_32-r_21=1m` and `r_42=r_31=sqrt((1)^2+(1)^2) =sqrt2m` substituting the proper values with sign in eqn ii we get `U=(9.0xx10^9)(10^-6)(10^-6)[((4)(-3))/1+((4)(2))/sqrt2+((4)(2))/(1)+((-3)(2))/1+((-3)(1))/sqrt2+((2)(1))/1]` `=(9.0xx10^-3)[-12+5/sqrt2]` `=-7.62xx10^-2J`

Discussion

1403.	A point charge `q_1=9.1muC` is held fixe at origin. A second pont charge `q_2=-0.42muC` and `a` mass `3.2xx10^-4kg` is placed on the x-axis, `0.96m` from the origin. The second point charge is released at rest. What is its speed when it is `0.24m` from the origin?
Answer» Correct Answer - B From conservation of mechanical energy, we have Decrease in electrostatic potential =Increase in kinetic energy or `1/2 mv^2=U_i-U_f=(q_1q_2)/(4piepsilon)(1/r_i-1/r_f)` `=(q_1q_2)/(4piepsilon_0)((r_f-r_i)/(r_ir_f))` `:. V=sqrt((q_1q_2)/(2piepsilon_0m)((r_f-r_i)/(r_ir_f)))` `=sqrt(((9.1xx10^-6)(-0.42xx10^-6)xx2xx9xx10^9)/(3.2xx10^-4)((0.24-0.96)/((0.24)(0.96))))` `=26m//s`

Discussion

1404.	A point charge `q_1 =1.0muC` is held fixed at origin. A second point charge `q_2 = -2.0 muC` and a mass `10^-4` kg is placed on the x-axis, 1.0 m from the origin. The second point charge is released from rest. What is its speed when it is 0.5 m from the origin?
Answer» Correct Answer - A `K_i+U_i=K_f+U_f` `:. 1/(4piepsilon_0)(q_1q_2)/r_i=1/2mv^2+1/(4piepsilon_0) (q_1q_2)/r_f` `:.v=sqrt(2/m(1/(4piepsilon_0))(q_1q_2)(1/r_i-1/r_f)))` `sqrt(2/10^-4(9xx10^9)(-2xx10^-12)(1/1.0-1/0.5))` `=18.97m//s`

Discussion

1405.	Two capacitors of capacitances `10muF and 20muF` are connected in series across a potential difference of 100V. The potential difference across each capacitor is respectivelyA. 66.67 V, 33.33 VB. 60 V, 40 VC. 50 V, 50 VD. 90 V, 10 V
Answer» Correct Answer - A `V_(1)=Q/C_(1)=(VC_(2))/(C_(1)+C_(2))=(100xx20xx10^(-6))/(30xx10^(-6))` `=66.67V` `therefore" "V_(2) = V-V_(1)=100-66.67=33.33V`

Discussion

1406.	A point charge `q_1=+2.40muC` is held stationary at the origin. A second point charge `q_2=-4.30muC` moves from the point x=0.150 m, y=0 to the point x=0 0.250 m, y=0.250 m. How much work is done by the electric force on `q_2`?
Answer» Correct Answer - C `W=-/_U=U_i-U_f=q_2V_i-q_2V_f` `=q_2((kq_1)/r_1)-q_2((kq_1)/r_f)` `=kq_1q_2(1/r_i-1/r_f)` `=(9xx10^9)(2.4xx10^-6)(-4.3xx10^6)` `(1/0.15-1/(0.25sqrt2))` `=-0.356J`

Discussion

1407.	A variable condenser is permanetly connect to a `100V` battery. If the capacity is charged from `2muE` to `10muF`, then change in energy is equal toA. `2xx10^(-2)J`B. `2.5xx10^(-2)J`C. `6.5xx10^(-2)J`D. `4xx10^(-2)J`
Answer» Correct Answer - D `deltaE=1/2C_(2)V^(2)-1/2C_(1)V^(2)` `=1/2xx10xx10^(-6)xx10^(4)-1/2 2xx10^(-6)xx10^(4)` `=4xx10^(-2)J`

Discussion

1408.	The capacity of a parallel plate air capacitor is `10muF` and it is given a charge of `40muC`. The electrical energy stored in the capacitor isA. 400 ergB. 600 ergC. 800 ergD. 900 erg
Answer» Correct Answer - C `E=Q^(2)/(2C)=((40xx10^(-6))^(2))/(2xx10xx10^(-6))` `=80xx10^(-6)J` = 800 erg.

Discussion

1409.	A capacitor of capacity `10muF` is subjected to charge by a battery of 10 V. Calculate the energy stored in the capacitor.A. `2xx10^(-7)J`B. `3xx10^(-5)J`C. `5xx10^(-4)J`D. `8xx10^(-6)J`
Answer» Correct Answer - C Given, capacity, `C=10muF=10xx10^(-6)F` Voltage, V = 10 V, Energy, E = ? Energy stored in the capacitor, `E=1//2CV^(2)` Now, put the values and calculate the required energy of capacitor. `E=(1)/(2)CV^(2)=(1)/(2)xx10xx10^(-6)xx10xx10` `E=5xx10^(-4)J`

Discussion

1410.	If the work done in bringing a charge of 10-18 C from infinity to point P is 2 × 10-17 J, what is the electric potential at P?
Answer» V =\(\cfrac{W}{q_0}\) = \(\cfrac{2\times10^{-17}J}{10^{-18}C}\) = 20 volts is the electric potential at P.

1410.

If the work done in bringing a charge of 10-18 C from infinity to point P is 2 × 10-17 J, what is the electric potential at P?

Answer»

V =\(\cfrac{W}{q_0}\) = \(\cfrac{2\times10^{-17}J}{10^{-18}C}\)

= 20 volts is the electric potential at P.

Discussion

1411.	A metallic sphere A isolated from ground is charged to +50 µC. This sphere is brought in contact with other isolated metallic sphere B of half the radius of sphere A. The charge on the two sphere will be now in the ratio (A) 1 : 2 (B) 2 : 1 (C) 4 : 1 (D) 1 : 1
Answer» Correct answer is (D) 1 : 1

Discussion

1412.	Three identical charges are placed at corners of a equilateral triangel of side l. If force between any two charges is F, the work required to double the dimensiions of triangle isA. `-3Fl`B. `3Fl`C. `(-3//2)Fl`D. `(3//2)Fl`
Answer» Correct Answer - C `W=/_U_i` `=U_f-U_i` `=3[1/(4piepsilon_0).(qq)/(2l)]-3[1/(4piepsilon_0).(qq)/l]` `=(-3/2)(1/(4piepsilon_0).q^2/l^2)l=-3/2Fl`

Discussion

1413.	Charges Q, 2Q and 4Q are uniformly distributed in three dielectric solid spheres 1, 2 and 3 of radii `R//2`, R and 2R respectively, as shown in figure. If magnitude of the electric fields at point P at a distance R from the centre of sphere 1,2 and 3 are `E_1, E_2 and E_3` respectively, then A. `E_(1) gt E_(2) E_(3)`B. `E_(3) gt E_(1) E_(2)`C. `E_(2) gt E_(1) E_(3)`D. `E_(3) gt E_(2) E_(1)`
Answer» Correct Answer - C `E_(1) = (1)/(4pi in_(0)) (Q)/(R^(2)) , E_(2) = (1)/(4pi in_(0)) (2Q)/(R^(2))` , `E_(3) = (1)/(4pi in_(0)) ((4Q) R)/(8 R^(3)) = (1)/(4pi in_(0)) (Q)/(2 R^(2))` Thus `E_(2) gt E_(1) gt E_(3)`

Discussion

1414.	Charges Q, 2Q and 4Q are uniformly distributed in three dielectric solid spheres 1, 2 and 3 of radii `R//2`, R and 2R respectively, as shown in figure. If magnitude of the electric fields at point P at a distance R from the centre of sphere 1,2 and 3 are `E_1, E_2 and E_3` respectively, then A. `E_(1) gt E_(2) gt E_(3)`B. `E_(3) gt E_(1) gt E_(2)`C. `E_(2) gt E_(1) gt E_(3)`D. `E_(3) gt E_(2) gt E_(1)`
Answer» Correct Answer - C

Discussion

1415.	Figure shown an imaginary cube of edge L/2. A uniformly Charged rod of length L moves towards left at a small but constant speed v. At t=0, the left end just touches the centre of the cube opposite it. Which of the graphs shown in figure represents the flux of the electic field through the cube as the rod goes through it? A. aB. bC. cD. d
Answer» Correct Answer - D

Discussion

1416.	Eight point charges (can be assumed as small spheres uniformly charged and their centres at the corner of the cube) having values q each are fixed at vertices of a cube. The electric flux through square surface ABCD of the cube is A. `q/(24 in_(0))`B. `q/(12 in_(0))`C. `q/(6 in_(0))`D. `q/(8 in_(0))`
Answer» Correct Answer - C

Discussion

1417.	Fig shows a closed surface surrounding some electric charges (a) what is the net electric flux through the surface? (b) Is the electric flux directed inward or outward from the surface ?
Answer» (a) Here, total charge inside the surface : `q = -6.7 muC + 3.2 muC = -3.5 muC` As `phi_(E) = (q)/(in_(0)) = (-3.5xx10^(-6))/(8.85xx10^(-12))` `= -3.95xx10^(5) Nm^(2) C^(-1)` (b) As `phi_(e)` is negative, it is directed Inwards.

Discussion

1418.	In the following diagrams a particle with small charge `-q` is free to move up or down , but not sideways near a larger fixed charge `Q`.The small charge is in equilibrium because in the positions shown ,the electrical upward force is equal to the weight of the particle .Which statement os true? A. In fig.`(A) ,-q` is in stable equilibriumB. In fig.`(A) ,-q` is in neutral equilibriumC. In fig.`(B) ,-q` is in stable equilibriumD. Neither in fig.`A` nor in `B,-q` is in stable equilibrium
Answer» Correct Answer - 3 In first diagram , if we displace `-q` in downward direction , electric force on it decreases , `mg != F_(e )` , it will move down (unstable equilibrium). In second diagram , if we displace `-q` in downward direction , electric force on it increases , `F_(e ) gt mg` , net force restores `-q` to its original position (unstable equilibrium).

Discussion

1419.	Electric charges are distributed in a small volume. The flux of the electric field through a spherical surface of radius 20 cm surrounding the total charge is 50 V-m. The flux over a concentric sphere of radius 40 cm will be :A. 50 V-mB. 75 V-mC. 100 V-mD. 200 V-m
Answer» Correct Answer - A

Discussion

1420.	Electric charge are distributed in a small vouume. The flux of the electric field through a spherical surface of rasius 10cm surrounding the total charge is 25 V m. The flux over a concentric sphere of radius 20 cm will beA. `25 V - m`B. `50 V-m`C. `100 V-m`D. `200 V-m`
Answer» Correct Answer - 1 Total charge inside sphere of `20 cm` radius remains same.

Discussion

1421.	The electric charges are distributed in a small volume. The flux of the electric field through a spherica surface of radius 10 cm surrounding the total charge is `20 V - m`. The flux over a concentric sphere of radius 20 cm will beA. 20 VmB. 10 VmC. 40 VmD. 5 Vm
Answer» Correct Answer - A

Discussion

1422.	Van de Graff generator producesA. 1. high voltage and high currentB. 2.high voltage and low currentC. 3.low voltage and high currentD. 4. low voltage and low current
Answer» Correct Answer - B

Discussion

1423.	Van de Graff generator producesA. high voltage and high currentB. high voltage and low currentC. low voltage and high currentD. low voltage and low current
Answer» Correct Answer - B

Discussion

1424.	Van de Graff generator is used to produce high energetic charged particles of energy of aboutA. 10 MeVB. 50 MeVC. 100 MeVD. 0.5 MeV
Answer» Correct Answer - A

Discussion

1425.	Two identical particles of charge `q` each are connected by a massless spring of force constant `k`. They are placed over a smooth horizontal surface. They are released when the separation between them is `r` and spring is unstretched. If maximum extension of the spring is `r`, the value of `k` is (neglect gravitational effect) A. `(q)/(4r)sqrt((1)/(pi epsilon_(0)r))`B. `(q)/(2r)sqrt((1)/(pi epsilon_(0)r))`C. `(2q)/(r)sqrt((1)/(pi epsilon_(0)r))`D. None of these
Answer» Correct Answer - D

Discussion

1426.	The ratio of electric and gravitational force between two protons.Charge of each proton is `1.6times10^(-19)C` mass is `1.67times10^(-27)Kg` and G=`6.67times10^(-11)Nm^(2)Kg^(-2)` .A. (A) `1.23times10^(36)`B. (в) `10^(20)`C. (С) `10^(15)`D. (D) `5N `
Answer» Correct Answer - A

Discussion

1427.	In the last question, the two particles A and B are initially held at a distance `r=(qQ)/(2pi in_(0)m u^(2))` apart. Particle B is projected directly towards A with velocity u and particle A is released simultaneously. Find the velocity of particle A after a long time. Consider coulomb force only.
Answer» Correct Answer - `((1+sqrt(3))/(2))u`

Discussion

1428.	Equipotential surfaces are perpendicular to field lines. Why ?
Answer» No work is done in moving a charge from one point on equipotential surface to the other. Therefore, component of electric field intensity along the equipotential surface is zero it means, the electric field intensity is perpendicular to equipotential surface. Hence, the surface is perpendicular to field lines.

Discussion

1429.	The equipotential surfaces of certain field are shown in figyre, It is known that ` v_1 gt v_2`. Use this pattern to reproduce approximately the lines of this field and indicate their directon. Determine the region in which the intensity if the field is highest .
Answer» Correct Answer - Field intensity will be higher in the region where equipotential surface ar dencser .

Discussion

1430.	Which of the following is NOT the property of equipotential surfaces?(A) They do not intersect each other. (B) They are concentric spheres for uniform electric field. (C) Potential at all points on the surface has constant value. (D) Separation of equipotential surfaces increases with decrease in electric field.
Answer» (B) They are concentric spheres for uniform electric field.

Discussion

1431.	Two isolated, charged conducting spheres of radii R , and R produce the same electric field near their surfaces. The ratio of electric potentials on their surfaces is-(a) \(\frac{R_1}{R_2}\)(b) \(\frac{R_2}{R_1}\) (c) \(\frac{R_1}{R_2^2}\)(d) \(\frac{R_2^2}{R_1^2}\)
Answer» Correct answer is (b) \(\frac{R_2}{R_1}\)

Discussion

1432.	Which of the following is not a property of equipotential surfaces? (a) they do not cross each other (b) they are concentric spheres for uniform electric field (c) the rate of change of potential with distance on them is zero (d) they can be imaginary spheres.
Answer» (b) they are concentric spheres for uniform electric field

Discussion

1433.	A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled,then the outward electric flux will be (a) reduced to half (b) doubled (c) becomes 4 times (d) remains the same
Answer» (d) remains the same

Discussion

1434.	A charge `Q` is enclosed by a Gaussian spherical surface of radius `R`. If the radius is doubled, then the outward electric flux willA. be reduced to halfB. remain the sameC. be doubledD. increase four times
Answer» Correct Answer - B `"Total flux"=("Net enclosed charge")/(epsilon_(0))` Hence, we cany say the electric flux depends only on net enclosed charge by surface.

Discussion

1435.	Why should electrostatic field be zero inside a conductor ?
Answer» In the static equilibrium, there is no current inside, or on the surface of the conductor, Hence the electric field is zero everywhere inside the conductor. Alternatively, Since the charge inside the conductor is zero, the electric field also zero. OR Alternatively, Since the conductor is uncharged so the electric field inside it is zero.(or any other logically valid answer.)

1435.

Why should electrostatic field be zero inside a conductor ?

Answer»

In the static equilibrium, there is no current inside, or on the surface of the conductor, Hence the electric field is zero everywhere inside the conductor.

Alternatively,

Since the charge inside the conductor is zero, the electric field also zero.

OR

Alternatively,

Since the conductor is uncharged so the electric field inside it is zero.(or any other logically valid answer.)

Discussion

1436.	Two equal negative charges `-q` are fixed at points `(0, -a)` and `(0,a)` on y-axis. A poistive charge Q is released from rest at point `(2a, 0)` on the x-axis. The charge Q willA. execute simple harmonic motion about the origineB. move to the origin and remain at restC. move to infinityD. execute oscillatory but not simple harmonic motion.
Answer» Correct Answer - D ` F_R =- 2F cos theta` ` F_R =- 2 (KQq.xa)/((x^2 +a^2)^(3//2))` Since ` x gt gt a`, so particel will excute oscillatory motion.

Discussion

1437.	The figure shows the electric field lines in the vicinity of two point charges. Which one of the following statements concerning this situation is true ?A. `q_1` is negatuve and `q_1` is positiveB. The magnitude of ratio `(q_2//q_1)` is less than oneC. Both `q_1` and `q_2` havve the same sign of charge D. The electric field is strongest midway between the charges
Answer» Correct Answer - B Since field line are originating gron ` q_1` and terminating at ` q_2` to ` q_1` is lessthab ` q_1` so ` q_2 //q_1 lt 1`.

Discussion

1438.	Electric flux through a surface of area ` 100m^2` lying in the xy plane is (in V-m) if `vec E= hat i+ sqrt 2hat j + sqrt 3 hat k-`.A. ` 100`B. ` 141.4`C. ` 17. 2`D. ` 200`
Answer» Correct Answer - C ` phi _E = vec E.vec A = (hat I + sqrt 2 hat I + sqrt 3 hat k ) . ( 100 hat k)` ` phi_E = 100 sqrt 3 = 173. 2 `.

Discussion

1439.	Two copper balls, each weighing `10 g` are kept in air `10 cm` apart. If one electron from every `10^(6)` atoms in trandferred from one ball to the other, the coulomb force between them is (atomic weight of copper is `63.5`)A. `2.0 xx 10^(10)N`B. `2.0 xx 10^(4) N`C. `2.0 xx 10^(8)N`D. `2.0 xx 10^(6)N`
Answer» Correct Answer - C

Discussion

1440.	An alpha particle of energy `5 MeV` is scattered through `180^(@)` by a found uramiam nucleus . The distance of closest approach is of the order ofA. 1 ÅB. `10^(-10)` cmC. `10^(-12)` cmD. `10^(-15)` cm
Answer» Correct Answer - C

Discussion

1441.	What is the equivalent capacitance of the system of capacitors between `A & B` A. `(7)/(6)C`B. 1.6 CC. CD. None of these
Answer» Correct Answer - B

Discussion

1442.	A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to:A. `-(Q)/(2)`B. `-(Q)/(4)`C. `+(Q)/(4)`D. `+(Q)/(2)`
Answer» Correct Answer - B

Discussion

1443.	Which of the following molecules is nonpolar? (A) N2O (B) H2O (C) HCl (D) CO2
Answer» Correct option is (D) CO₂

Discussion

1444.	If the above question, the potential has correct relations as given=A. `V_(A) gt V_(B) gt V_(C) gt V_(D)`B. `V_(A) gt V_(B) ge V_(C) gt V_(D)`C. `V_(D)=V_(C)=V_(B)=V_(A)`D. `V_(C) lt V_(B) gt V_(A) gt V_(D)`
Answer» Correct Answer - C

Discussion

1445.	An electron is revolving around a proton. The total work done in one revolution by electric force on the electron will be zero if the trajectory of the electron isA. circular onlyB. elliptical onlyC. any closed curveD. not possible
Answer» Correct Answer - C

Discussion

1446.	`S_1`: When a positively charged particle is released in an electric field , in its subsequent motion,it may or may not move along the electric field line passing through the point it has been released. `S_2`: In electrostatic, conductors are always equipotential surfaces. `S_3`: The flux through a closed Gaussian surface is non-zero. The electric field at some point on the Gaussian surface may be zero.A. TTFB. FTFC. TTTD. FFF
Answer» Correct Answer - C

Discussion

1447.	Show that the SI unit of `epsilon_0` may be written as farad `meter^(-1)`.
Answer» Yes, in S.I. units, the capacitance of a sphere is given by `C = 4pi in_(0) R, So, in_(0) = (C )/(4pi R)` , Clearly, SI Unit of `in_(0) is Fm^(-1)`

Discussion

1448.	Electric potential due to a dipole at a position `vec r` from its centre is: where `(K = 1/(4pi epsilon_0)`A. `(Kvec(p).vec(r))/(r^(3))`B. `(K.vec(p).vec(r))/(r^(2))`C. `(K.vec(P)xxvec(r))/(r^(3))`D. `(K.vec(p)xxvec(r))/(r^(2))`
Answer» Correct Answer - A

Discussion

1449.	Find the dimensions and units of `epsilon_0`
Answer» Correct Answer - A::B::C::D `F=1/(4pi epsilon_0) (q_1q_2)/r^2` `:. epsilon_0=(q_1q_2)/(4pi Fr^2)` Units and dimensions can be found by above equation.

Discussion

1450.	The mass of an electron is `9.11 x 10^-31` kg, that of a proton is `1.67 x 10^-27` kg. Find the ratio `F_e// F_g` of the electric force and the gravitational force exerted by the proton on the electron.-
Answer» Correct Answer - A::B::C `F_e=1/(4piepsilon_0)(q_1q_2)/r^2` `and F_g=G(m_1m_2)/r^2` `:. F_e/F_g=((1//4piepsilon_0)q_1q_2)/(Gm_1m_2)` `=((9xx10^+9)(1.6xx0^-19)^2)/((6.67xx10^-11)(9.11xx10^-31)(1.67xx10^-27))` `=2.27xx10^39`

Discussion

Explore topic-wise InterviewSolutions in .

Two points charges are located on the x-axis, `q_1=-1muC` at `x=0 and q_2=+1muc` at `x=1m`. a. Find the work that must be done by an external force to bring a third point charge `q_3=+1muC` from infinity to `x=2m`. b. Find the total potential energy of the system of three charges.

For charges `q_1=1muC, q_2=2muC, q_3=-3muC` and `q_4=4muC` are kept on the vertices of a square of side `1m`. Find the electric potential energy of this system of charges.

A point charge `q_1=9.1muC` is held fixe at origin. A second pont charge `q_2=-0.42muC` and `a` mass `3.2xx10^-4kg` is placed on the x-axis, `0.96m` from the origin. The second point charge is released at rest. What is its speed when it is `0.24m` from the origin?

A point charge `q_1 =1.0muC` is held fixed at origin. A second point charge `q_2 = -2.0 muC` and a mass `10^-4` kg is placed on the x-axis, 1.0 m from the origin. The second point charge is released from rest. What is its speed when it is 0.5 m from the origin?

Two capacitors of capacitances `10muF and 20muF` are connected in series across a potential difference of 100V. The potential difference across each capacitor is respectivelyA. 66.67 V, 33.33 VB. 60 V, 40 VC. 50 V, 50 VD. 90 V, 10 V

A point charge `q_1=+2.40muC` is held stationary at the origin. A second point charge `q_2=-4.30muC` moves from the point x=0.150 m, y=0 to the point x=0 0.250 m, y=0.250 m. How much work is done by the electric force on `q_2`?

A variable condenser is permanetly connect to a `100V` battery. If the capacity is charged from `2muE` to `10muF`, then change in energy is equal toA. `2xx10^(-2)J`B. `2.5xx10^(-2)J`C. `6.5xx10^(-2)J`D. `4xx10^(-2)J`

The capacity of a parallel plate air capacitor is `10muF` and it is given a charge of `40muC`. The electrical energy stored in the capacitor isA. 400 ergB. 600 ergC. 800 ergD. 900 erg

A capacitor of capacity `10muF` is subjected to charge by a battery of 10 V. Calculate the energy stored in the capacitor.A. `2xx10^(-7)J`B. `3xx10^(-5)J`C. `5xx10^(-4)J`D. `8xx10^(-6)J`

If the work done in bringing a charge of 10-18 C from infinity to point P is 2 × 10-17 J, what is the electric potential at P?

A metallic sphere A isolated from ground is charged to +50 µC. This sphere is brought in contact with other isolated metallic sphere B of half the radius of sphere A. The charge on the two sphere will be now in the ratio (A) 1 : 2 (B) 2 : 1 (C) 4 : 1 (D) 1 : 1

Three identical charges are placed at corners of a equilateral triangel of side l. If force between any two charges is F, the work required to double the dimensiions of triangle isA. `-3Fl`B. `3Fl`C. `(-3//2)Fl`D. `(3//2)Fl`

Fig shows a closed surface surrounding some electric charges (a) what is the net electric flux through the surface? (b) Is the electric flux directed inward or outward from the surface ?

Electric charges are distributed in a small volume. The flux of the electric field through a spherical surface of radius 20 cm surrounding the total charge is 50 V-m. The flux over a concentric sphere of radius 40 cm will be :A. 50 V-mB. 75 V-mC. 100 V-mD. 200 V-m

Electric charge are distributed in a small vouume. The flux of the electric field through a spherical surface of rasius 10cm surrounding the total charge is 25 V m. The flux over a concentric sphere of radius 20 cm will beA. `25 V - m`B. `50 V-m`C. `100 V-m`D. `200 V-m`

The electric charges are distributed in a small volume. The flux of the electric field through a spherica surface of radius 10 cm surrounding the total charge is `20 V - m`. The flux over a concentric sphere of radius 20 cm will beA. 20 VmB. 10 VmC. 40 VmD. 5 Vm

Van de Graff generator producesA. 1. high voltage and high currentB. 2.high voltage and low currentC. 3.low voltage and high currentD. 4. low voltage and low current

Van de Graff generator producesA. high voltage and high currentB. high voltage and low currentC. low voltage and high currentD. low voltage and low current

Van de Graff generator is used to produce high energetic charged particles of energy of aboutA. 10 MeVB. 50 MeVC. 100 MeVD. 0.5 MeV

The ratio of electric and gravitational force between two protons.Charge of each proton is `1.6times10^(-19)C` mass is `1.67times10^(-27)Kg` and G=`6.67times10^(-11)Nm^(2)Kg^(-2)` .A. (A) `1.23times10^(36)`B. (в) `10^(20)`C. (С) `10^(15)`D. (D) `5N `

In the last question, the two particles A and B are initially held at a distance `r=(qQ)/(2pi in_(0)m u^(2))` apart. Particle B is projected directly towards A with velocity u and particle A is released simultaneously. Find the velocity of particle A after a long time. Consider coulomb force only.

Equipotential surfaces are perpendicular to field lines. Why ?

The equipotential surfaces of certain field are shown in figyre, It is known that ` v_1 gt v_2`. Use this pattern to reproduce approximately the lines of this field and indicate their directon. Determine the region in which the intensity if the field is highest .

Two isolated, charged conducting spheres of radii R , and R produce the same electric field near their surfaces. The ratio of electric potentials on their surfaces is-(a) \(\frac{R_1}{R_2}\)(b) \(\frac{R_2}{R_1}\) (c) \(\frac{R_1}{R_2^2}\)(d) \(\frac{R_2^2}{R_1^2}\)

Which of the following is not a property of equipotential surfaces? (a) they do not cross each other (b) they are concentric spheres for uniform electric field (c) the rate of change of potential with distance on them is zero (d) they can be imaginary spheres.

A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled,then the outward electric flux will be (a) reduced to half (b) doubled (c) becomes 4 times (d) remains the same

A charge `Q` is enclosed by a Gaussian spherical surface of radius `R`. If the radius is doubled, then the outward electric flux willA. be reduced to halfB. remain the sameC. be doubledD. increase four times

Why should electrostatic field be zero inside a conductor ?

Electric flux through a surface of area ` 100m^2` lying in the xy plane is (in V-m) if `vec E= hat i+ sqrt 2hat j + sqrt 3 hat k-`.A. ` 100`B. ` 141.4`C. ` 17. 2`D. ` 200`

An alpha particle of energy `5 MeV` is scattered through `180^(@)` by a found uramiam nucleus . The distance of closest approach is of the order ofA. 1 ÅB. `10^(-10)` cmC. `10^(-12)` cmD. `10^(-15)` cm

What is the equivalent capacitance of the system of capacitors between `A & B` A. `(7)/(6)C`B. 1.6 CC. CD. None of these

A charge q is placed at the centre of the line joining two equal charges Q. The system of the three charges will be in equilibrium if q is equal to:A. `-(Q)/(2)`B. `-(Q)/(4)`C. `+(Q)/(4)`D. `+(Q)/(2)`

Which of the following molecules is nonpolar? (A) N2O (B) H2O (C) HCl (D) CO2

If the above question, the potential has correct relations as given=A. `V_(A) gt V_(B) gt V_(C) gt V_(D)`B. `V_(A) gt V_(B) ge V_(C) gt V_(D)`C. `V_(D)=V_(C)=V_(B)=V_(A)`D. `V_(C) lt V_(B) gt V_(A) gt V_(D)`

An electron is revolving around a proton. The total work done in one revolution by electric force on the electron will be zero if the trajectory of the electron isA. circular onlyB. elliptical onlyC. any closed curveD. not possible

Show that the SI unit of `epsilon_0` may be written as farad `meter^(-1)`.

Electric potential due to a dipole at a position `vec r` from its centre is: where `(K = 1/(4pi epsilon_0)`A. `(Kvec(p).vec(r))/(r^(3))`B. `(K.vec(p).vec(r))/(r^(2))`C. `(K.vec(P)xxvec(r))/(r^(3))`D. `(K.vec(p)xxvec(r))/(r^(2))`

Find the dimensions and units of `epsilon_0`

The mass of an electron is `9.11 x 10^-31` kg, that of a proton is `1.67 x 10^-27` kg. Find the ratio `F_e// F_g` of the electric force and the gravitational force exerted by the proton on the electron.-