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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1601. |
A charge `+Q` is lying at the center of a circle. What is work done in carrying charge q from A to B, where A and B, both lie on the circle. |
| Answer» The circular path around the charge `+Q` is an eqipotential surface. As A and B lie on the circle i.e, on the equipotential surface, work done = 0. | |
| 1602. |
Around a point charge of `1 nC`, what is the distance of an equipotential surface of `0.9V` ? |
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Answer» Here `q = 1nC = 10^(-9) C, V = 0.9 V, r = ?` As `V = (q)/(4pi in_(0) r)` `:.r = (q)/(4pi in_(0) r) = (10^(-9)xx9xx10^(9))/(0.9) = 10m` |
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| 1603. |
When a proton approaches another fixed proton, what happens to : (a) the kinetic energy of the approaching proton (b) the electric potential energy potential energy of the system and (c ) the total energy of the system ? |
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Answer» (a) The kinetic energy of the approaching proton decreases. (b) The electric potential energy of the system increases because distance between the charges decreases. (c ) The total energy of the system remains the same because of the conservation of energy. |
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| 1604. |
The plate separation in a parallel plate condenser and plate area is A. If it is charged to V volt battery is diconnected then the work done increasing the plate separation to 2d will beA. `(3)/(2)(epsilon_(0)AV^(2))/(d)`B. `(epsilon_(0)AV^(2))/(d)`C. `(2epsilon_(0)AV^(2))/(d)`D. `(epsilon_(0)AV^(2))/(2d)` |
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Answer» Correct Answer - D |
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| 1605. |
Surface density of charge on a sphere of radius R in terms of electric intensity E at a distance in free space is `(epsi_(0)` = permittivity of free space)A. `in_(0)E(R/r)^(2)`B. `(in_(0)ER)/r^(2)`C. `in_(0)E(r/R)^(2)`D. `(in_(0)Er)/R^(2)` |
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Answer» Correct Answer - C The electric intensity out side the charged sphere in terms of surface charge density is given by, `E=(sigmaR^(2))/(in_(0)Kr^(2))` `therefore" "sigma=Ein_(0)K(r/R)^(2)` For free space K = 1 `therefore" "sigma=Ein_(0)(r/R)^(2)` |
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| 1606. |
An electric dipole is placed at rest in a uniform electric field, and released. How will it move ? |
| Answer» A torque will develop and align the electric dipole in the direction of the electric field, if the dipole is not aligned already. The dipole shall not move as net force on the dipole is Zero. | |
| 1607. |
The given figure gives electric line of force due to two charges `q_(1)` and `q_(2)`. What are the signs of the two charges ? A. Both are negativeB. Both are positiveC. `q_(1)` is positive but `q_(2)` is negativeD. `q_(1)` is negative but `q_(2)` is positive |
| Answer» Correct Answer - A | |
| 1608. |
What does `(q_(1) + q_(2)) = 0` signify ? |
| Answer» `q_(1) + q_(2) = 0, q_(1) = -q_(2).` Such a system of point charges is called an electric dipole. It is a pair of equal and opposite point charges separted by a small distance. | |
| 1609. |
A charged particale is free to move in an electric field. Will it always move along an electric line of force ? |
| Answer» If charged paricale was initally at rest, it will move along the direction of electric field. If initial velocity of the charged particle makes a certain angle with electric field, then the changed particle will not move along the line of force. | |
| 1610. |
Two concentric spheres kept in air have radii R and r. They have similar charge and equal surface charge density `sigma`. The electrical potential at their common centre is (where, `epsi_(0) =` permittivity of free space)A. `(sigma(R+r))/in_(0)`B. `(sigma(R-r))/in_(0)`C. `(sigma(R+r))/(2in_(0))`D. `(sigma(R+r))/(4in_(0))` |
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Answer» Correct Answer - A The potential outside the surface, on the surface and at any point inside the surface is same, `therefore" "V_(1)=1/(4piepsi_(0))q/R` `" "(thereforesigma=q/(4piR^(2))thereforeq=sigma4piR^(2))` `therefore" "V_(1)=1/(4piepsi_(0))(sigma4piR^(2))/R` `V_(1)=(sigmaR)/epsi_(0)` Similarly,`" "V_(2)=(sigmar)/epsi_(0)` Thus, the resultant potential is given by, `V=V_(1)+V_(2)` `=(sigmaR)/epsi_(0)+(sigmar)/epsi_(0)=sigma/epsi_(0)(R+r)` |
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| 1611. |
A metallic partical having no net charge is placed near a finite metal plate carrying a positive charge. The electric force on the particale will beA. towards the plateB. away from the plateC. parallel to the plateD. zero |
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Answer» Correct Answer - A |
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| 1612. |
A neutral spherical metallic object a is placed near a finite metal plate B carrying a positive charge. The electric force on the object will be :A. away from the plate BB. towards the plate BC. parallel to the plate BD. zero |
| Answer» Correct Answer - B | |
| 1613. |
Capacitor `C_(3)` in the circuit is variable capacitor (its capacitance can be varied). Graph is plotted between potential difference `V_(1)` (across capacitor `C_(1)`) versus `C_(3)`. Electric potential `V_(1)` approaches on asymptote of 10 volts as `C_(3) to infty` The value of C3 for which potential difference across `C_(1)` will become 8V, isA. `2 mu F`B. `6 mu F`C. `8 mu F`D. `4 mu F` |
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Answer» Correct Answer - A |
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| 1614. |
Four large identical metallic plates are placed as shown in the Figure. Plate 2 is given a charge Q. All other plates are neutral. Now plates 1 and 4 are earthed. Area of each plate is A. (a) Find charge appearing on right side of plate 3. (b) Find potential difference between plates 1 and 2. A. `(3)/(2) (Qd)/(epsi_(0)A)`B. `(Qd)/(epsi_(0)A)`C. `(3)/(4) (Qd)/(epsi_(0)A)`D. `(3Qd)/(epsi_(0)A)` |
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Answer» Correct Answer - C |
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| 1615. |
Two point charges q each are fixed at (a,0) and (-a,0). A third charge Q is placed at origin. Electrons potential energy of the system willA. increase if `Q` is slightly displaced along x-axisB. decrease if Q is slightly displaced along x-axisC. increase if Q is slightly displaced along y-axisD. decrease if Q is slightly displaced along y-axis |
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Answer» Correct Answer - A::D |
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| 1616. |
When a piece of polythene is rubbed with wool, a charge of `-2xx10^(-7) C` is developed on polythene. What is the amount of mass, which is transferred to polythene.A. `569xx10^(-19)`kgB. `6.25xx10^(-19)`kgC. `9.63xx10^(-19)`kgD. `11.38xx10^(-19)`kg |
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Answer» Correct Answer - D `n = q/e` `therefore" ""mass of n electrons"=q/exx9.1xx10^(-31)` `= 11.38xx10^(-19)kg` |
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| 1617. |
A conductor has been given a charge `-3 xx 10^(-7) C` by transferring electron. Mass increase (in kg) of the conductor and the number of electrons added to the conductor are respectivelyA. `2 xx 10^(-16)` and `2 xx 10^(31)`B. `5 xx 10^(-31)` and `5 xx 10^(19)`C. `3 xx 10^(-19)` and `9 xx 10^(16)`D. `2 xx 10^(-18)` and `2 xx 10^(12)` |
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Answer» Correct Answer - D |
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| 1618. |
Two charges of equal magnitudes and at a distance r exert a force F on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge isA. `F//8`B. `F//4`C. `4F`D. `F//16` |
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Answer» Correct Answer - D |
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| 1619. |
A conductor has been given a charge `-3 xx 10^(-7) C` by transferring electron. Mass increase (in kg) of the conductor and the number of electrons added to the conductor are respectivelyA. `2.4xx10^(-16)C`B. `4.4xx10^(-16)C`C. `5.5xx10^(-16)C`D. `6.6xx10^(-16)C` |
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Answer» Correct Answer - A `q="ne" = 1500xx1.6xx10^(-19)` `=2.4xx10^(-16)C` |
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| 1620. |
In `C - R` circuit, answer the following two questions During charging of `C - R` circuit let `t_(1)` and `t_(2)` be the time constant and initial charging current when capacitor is assumed to be filled by a perfect insulator and `t_(2)` and `i_(2)` be the corresponding values when it is assumed imperfect. ThenA. `t_(1) lt t_(2)`B. `i_(1) gt i_(2)`C. Both (a) and (b) are correctD. Both (a) and (b) are wrong |
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Answer» Correct Answer - C |
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| 1621. |
When the distance between two charged particles is halved, the force between them will becomeA. one-thirdB. one-halfC. four timesD. five times |
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Answer» Correct Answer - C `r_(2)=r_(1)/2,F_(2)=?` `Fprop1/r^(2)` `therefore" "F_(2)/F_(1)=(r_(1)/r_(2))^(2)=(r_(1)/(r_(1)/2))^(2)=4` `F_(2)=4F_(1)="four times"` |
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| 1622. |
In `C - R` circuit, answer the following two questions Dielectric constant of the slab between plates of a capacitor is 18 and its resistivity is `(4 pi xx 10^(3)) Omega - m`. Then time constant of this capacitor when directly connected to a battery will beA. `2 mu s`B. `3 mu s`C. `1 mu s`D. `9 mu s` |
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Answer» Correct Answer - A |
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| 1623. |
In a hydrogen atom, the distance between the electron and proton is `2.5 xx 10^(-11)m`. The electricl force of attraction between then will beA. `6.3xx10^(-8)N`B. `8.2xx10^(-8)N`C. `9.6xx10^(-8)N`D. `12.2xx10^(-8)N` |
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Answer» Correct Answer - B `F=1/(4piin_(0))xx(q_(1)q_(2))/r^(2)` `=(9xx10^(9)xx1.6xx1.6xx10^(-38))/((5.3xx10^(-11))^(2))` `=8.2xx10^(-8)N` |
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| 1624. |
The electric field at a point due to a point a charge is `30 N//C`, and the electric potential at that point is `15 J//C`. Calcualte the distance of the point from the charge and the magnitude of the charge. |
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Answer» Correct Answer - `0.5 m ; 0.83xx10^(-9)C` Here, `E = (q)/(4pi in_(0) r^(2)) = 30 NC^(-1)` …(i) `V = (q)/(4pi in_(0) r) = 15 JC^(-1)` …(ii) Divide (ii) by (i), we get `r = (1)/(2) = 0.5m` Put in (ii), `9xx10^(9) (q)/(1//2) = 15` `q = (15)/(18) xx10^(-9) = 0.83xx10^(-9) C` |
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| 1625. |
A point charge of `10^(-8) C` is situated at the origin of co-ordinatges. Find the potential difference between the points `A(4,4,2) and B(1,2,2)`. |
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Answer» Correct Answer - `-15V` Here, `q = 10^(-8) C, vec(r_(A)) = 4 hat(i) + 4 hat(j) + 2 hat(k)` so that `r_(A) = sqrt(4^(2) + 4^(2) + 2^(2)) = 6` `vec(r_(B)) = 1 hat(i) + 2 hat(j) + 2 hat(k)`, so that `r_(B) = sqrt(1^(2) + 2^(2) + 2^(2)) = 3`. `V_(A) - V_(B) = (q)/(4pi in_(0)) [(1)/(r_(A)) - (1)/(r_(B))]` `= 9xx10^(9)xx10^(-8) [(1)/(6) - (1)/(3)] = -15 V` |
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| 1626. |
We may define electrostatic potential at a point in an electrostatic field as the amount of work done in moving a unit positive test charge from infinity to that point against the electrostatic forces, along any path. Due to a single charge `q` , potential at a point distant `r` from the charge is `V = (q)/(4pi in_(0)r)`. The potential can be positive or negative. However, it is scalar quantity. The total amount of work done in bringing various charges to their respective postions from infinelty large mutual separations gives us the electric potential energy of the system of charges. Whereas electric potentail is measured in volt, electric potential energy is measured in joule. You are given a square of each side 1.0 metre with four charges `+1xx10^(-8) C, -2xx10^(-8)C, +3xx10^(-8)C` and `+2xx10^(-8) C` placed at the four corners of the square. With the help of the passage given above, choose the most approprite alternative for each of the following questions : Electric potentail and electric potential energyA. both are scalarsB. both are vectorsC. electric potential is scalar and electric potential energy is vector,D. electric potentail is vector and electric potential energy is scalar. |
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Answer» Correct Answer - A Both electric potential and electric potential energy are scaler quantities, as they reprsent work done. |
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| 1627. |
We may define electrostatic potential at a point in an electrostatic field as the amount of work done in moving a unit positive test charge from infinity to that point against the electrostatic forces, along any path. Due to a single charge `q` , potential at a point distant `r` from the charge is `V = (q)/(4pi in_(0)r)`. The potential can be positive or negative. However, it is scalar quantity. The total amount of work done in bringing various charges to their respective postions from infinelty large mutual separations gives us the electric potential energy of the system of charges. Whereas electric potentail is measured in volt, electric potential energy is measured in joule. You are given a square of each side 1.0 metre with four charges `+1xx10^(-8) C, -2xx10^(-8)C, +3xx10^(-8)C` and `+2xx10^(-8) C` placed at the four corners of the square. With the help of the passage given above, choose the most approprite alternative for each of the following questions : Potential energy fo the system of four system of four charges isA. `12.73xx10^(7) J`B. `-6.4xx10^(7) J`C. `12.73xx10^(-9) J`D. `-12.73xx10^(-9) J` |
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Answer» Correct Answer - B As potential energy `= (q_(1) q_(2))/(4pi in_(0)r)` `:.` Potential energy of the sytem of charges `= 9xx10^(9)xx` `[((1xx10^(-8))(-2xx10^(-8)))/(1.0) + ((-2xx10^(-8))(3xx10^(-8)))/(1.0)` `+ ((3xx10^(-8))(2xx10^(-8)))/(1.0) + ((2xx10^(-8))(1xx10^(-8)))/(1.0)]` `+ 9xx10^(9)xx` `[((1xx10^(-8))(3xx10^(-8)))/(sqrt(2)) + ((2xx10^(-8))(-2xx10^(-8)))/(sqrt(2))]` `= 0+ (9xx10^(9) (-10^(16)))/(sqrt(2)) = -6.4xx10^(-7) J` |
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| 1628. |
The force of attraction between two charges `+30 xx 10^(-9)C and -20 xx 10^(-9)C` seperated by a distance of 020m is found to be `5 xx 10^(-5)N`. Find the relative permittivity of the medium.A. 2 NB. 50 NC. 0.5 ND. 10 N |
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Answer» Correct Answer - A `k=F_(a)/F_(m)" "thereforeF_(m)=F_(a)/k=2N` |
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| 1629. |
The force exerted on a 3 C of charge placed at a point in an electric field is 9 N. Calculate the electric field strength at the point.A. `375N//C`B. `1500N//C`C. `1666N//C`D. `2000N//C` |
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Answer» Correct Answer - B `E=F/q=(2.25)/(15xx10^(-4))=1500N//C` |
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| 1630. |
What is the potential at the centre of a square of each side 1.0 meter, when four charges `+1xx10^(-8)C, -2xx10^(-8) C, +3xx10^(-8)C and +2xx10^(-8)C` are placed at the four corners of the square. |
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Answer» Correct Answer - `5.1xx10^(2)V` Diagonal of sqare `= sqrt(1^(2) + 1^(2)) = sqrt(2)` Distance of each charge from the centre `r = (sqr(2))/(2) = (1)/(sqrt(2))`, use `V = (Sigma q)/(4pi in_(0) r)` |
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| 1631. |
Two point charges `q_(1)=2xx10^(-3) C` and `q_(2)=-3xx10^(-6) C` are separated by a distance `x = 10` cm. Find the magnitude and nature of the force between the two charges.A. 4 NB. 5 NC. 9 ND. 13 N |
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Answer» Correct Answer - C `F=1/(4piin_(0))xx(q_(1)q_(2))/r^(2)` `therefore" "F=(9xx10^(9)xx5xx10^(-6)xx2xx10^(-6))/((10xx10^(-2))^(2))=9N` |
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| 1632. |
Find out potential energy of the two point charge system having charges `q_(1)` and `q_(2)` separated by distance r. |
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Answer» Let both the charge be placed at a very large separation initially. Let, `W_(1)=` work done in bringing charge `q_(1)` in absence of `q_(2)=q_(1) (V_(f)-V_(i))=0` `W_(2)=` work done in bringing charge `q_(2)` in presence of `q_(1)=q_(2)(V_(f)-V_(i))=q_(2) (Kq_(1)//r-0)` `:. PE=W_(1)+W_(2)=0+Kq_(1)q_(2)//r=Kq_(1)q_(2)//r` |
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| 1633. |
Consider a cube of uniform charge density `rho`. The ratio of electrostatic potential at the centre of the cube to that at one of the corners of the cube is |
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Answer» Correct Answer - `2:1` |
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| 1634. |
If potential (in volts) in a region is expressed as `V (x, y, z) = 6xy - y + 2yz`, the electric field (in `N//C)` at point `(1, 1, 0)` isA. `-(3hati _5hatj +3hatk)`B. `-(6hati +5hatj +2hatk)`C. `-(2hati =3hatj +hatjk)`D. `-(6hati +9hatj + hatk)` |
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Answer» Correct Answer - B |
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| 1635. |
If potential (in volts) in a region is expressed as `V (x, y, z) = 6xy - y + 2yz`, the electric field (in `N//C)` at point `(1, 1, 0)` isA. `-(6 hat(i) + 9 hat(j) + hat(k))`B. `-(3 hat(i) + 5 hat(j) + 3 hat(k))`C. `-(6 hat(i) + 5 hat(j) + 2 hat(k))`D. `-(2 hat(i) + 3 hat(j) + hat(k))` |
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Answer» Correct Answer - C Given, `V = 6 xy-y +2 yz` `vec(E) = [(del V)/(del x) hat(i) + (del V)/(del y) hat(j) + (del V)/(del z) hat(k)]` `vec(E) = -{(del)/(del x) [6 xy - y + 2 yz] hat(i) + (del)/(del y) [6xy - y +2yz] hat(j)` `+ (del)/(dz) [ 6 xy - y+ 2 yz) hat(k) }` `= -{(6y) hat(i) + (6x - 1 + 2z) hat(j) +(2y) hat(k)}` `vec(E)_(1,1,0) = -{(6x1) hat(i) + (6xx1-1+2xx0) hat(j) + (2xx1) hat(k)]` `= -(6 hat(i) + 5 hat(j) + 2 hat(k))` |
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| 1636. |
A spherical conductor `A` of radius `r` is placed concentrically inside a conducting shell `B` of radius `R(R gt r)`. A charge `Q` is given to `A` , and then `A` is joined to `B` by a metal wire. The charge flowing from `A` to `B` will beA. `Q(R/(R+r))`B. `Q(r/(R+r))`C. `Q`D. zero |
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Answer» Correct Answer - C |
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| 1637. |
A spherical conductor `A` of radius `r` is placed concentrically inside a conducting shell `B` of radius `R(R gt r)`. A charge `Q` is given to `A` , and then `A` is joined to `B` by a metal wire. The charge flowing from `A` to `B` will beA. `Q((R )/(R + r))`B. `Q((r )/(R + r))`C. `Q`D. Zero |
| Answer» Correct Answer - 3 | |
| 1638. |
STATEMENT -1 : Consider a conducting sphere of radius `R`. Now a charge `q` is placed in front of shphere . Electric potential at point `O` is `(Kq)/r` STATEMENT -2: Electric potential at the centre of sphere due to induced charges is zero.A. Statement -1 is True , Statement -2 is True , Statement -2 is a correct explanation for Statement -10B. Statement -1 is Tre , Statement -2 is True , Statement -2 is NOT a correct explanation for statement -1.C. Statement -1 true, Statement -2 is False.D. Statement -1 is False , Statement -2 is true. |
| Answer» Correct Answer - A | |