1638 + Interview Questions in ELECTROSTATICS IN GENERAL AWARENESS Page 18 InterviewSolution

851.	Four point charge `q, - q, 2Q` and Q are placed in order at the corners A, B, C and D of a square. If the field at the midpoint of CD is zero then the value of `q//Q` is `(5 sqrt5)/(x)`. Find the value of x.
Answer» Correct Answer - 2

Discussion

852.	If a positive charge is shifted from a low - potential region to a high- potential region, the electric potential energyA. IncreasesB. DecreasesC. May increase or decreaseD. Remains constant
Answer» Correct Answer - C

Discussion

853.	A hollow charged metal sphere has radius `r`. If the potential difference between its surface and a point at a distance `3r` from the centre is V, then electric field intensity at a distance `3r` isA. V/6rB. V/4rC. V/3rD. V/2r
Answer» Correct Answer - A

Discussion

854.	A charge `+q` is fixed at each of the points `x=x_0`, `x=3x_0`, `x=5x_0`,…………`x=oo` on the x axis, and a charge `-q` is fixed at each of the points `x=2x_0`, `x=4x_0`, `x=6x_0`, …………`x=oo`. Here `x_0` is a positive constant. Take the electric potential at a point due to a charge Q at a distance r from it to be `Q//(4piepsilon_0r)`.Then, the potential at the origin due to the above system of
Answer» Correct Answer - D

Discussion

855.	A hollow metal sphere of radius 5 cms is charged such that the potential on its surface is 10 volts. The potential at the centre of the sphere isA. ZeroB. 10 voltC. Same as at a point 5 cm away from the surfaceD. Same as at a point 25 cm away from the centre
Answer» Correct Answer - B

Discussion

856.	A hollow sphere of radius 2R is charged to V volts and another smaller sphere of radius R is charged to V/2 volts. Now the smaller sphere is placed inside the bigger sphere without changing the net charge on each sphere. The potential difference between the two spheres would beA. `(3V)/(2)`B. `(V)/(4)`C. `(V)/(2)`D. V
Answer» Correct Answer - B

Discussion

857.	A hollow sphere of radius 2R is charged to V volts and another smaller sphere of radius R is charged to `V//2` volts. Then the smaller sphere is placed inside the bigger sphere without changing the net charge on each sphere. The potential difference between the two spheres would becomes `V//n`. find value of `n`
Answer» Correct Answer - 4

Discussion

858.	A conducting sphere of radius R is charged to a potential of V volts. Then the electric field at a distance `r ( gt R)` from the centre of the sphere would beA. `(V)/(r)`B. `(R^(2)V)/(r^(3))`C. `(RV)/(r^(2))`D. `(rV)/(R^(2))`
Answer» Correct Answer - C

Discussion

859.	In going from the surface of a charged conducting sphere towards the centre of the sphere the electric fieldA. increasesB. decreasesC. remains the same as on the surfaceD. remains zero at every place
Answer» Correct Answer - D

Discussion

860.	An electron and a proton are freely situated in an electric field. Will the electric forces on them be equal? Will their acceleration be equal? Explain with reason.A. zeroB. unityC. ratio of the mass of proton and electronD. ratio of the mass of electron and proton
Answer» Correct Answer - C

Discussion

861.	A metal sphere has a charge of `-6.5 muC`. When `5xx10^(13)` electrons are removed from the sphere, what would be the net charge on it?
Answer» Here, `(q_(1)) = (6.5) muC` , and `q_(2) =n e = 5xx10^(13) (1.6xx10^(-19))C` `= 8.0xx10(-6)C=8.0 mu C` As electronics are removed from the sphere, `q = q_(1)+q_(2)=6.5 muC+8.0 muC = 1.5 muC `

Discussion

862.	If a body gives out `10^(9)` electrons every second, how much time required to get a total charge of `1 C` from it ?
Answer» Here,` n = 10^(9)C` Charge `given//sec`, `q=n e = 10^(9)xx1.6xx10^(-19)C` = `(1.6xx10^(-10))C` Total charge,`Q = 1 C` :. Time required = `(Q)/(q) = (1)/(1.6xx10^(-10)) sec` `6.25xx10^(9)s = (6.25xx10^(9))/(3600xx24xx365)` year `(198.18)` year

Discussion

863.	Which is bigger, a coulomb or charge on an electron ? How many electronic charges from one coulomb of charge ?
Answer» A coulomb of charge is bigger than the charge is begger than the charge on an electron. Maganitude of charge on one electron. `e =(1.6xx10^(-19))` coulomb, Number of electronic charges in one coulomb, `n = (q)/(e) = (1)/(1.6xx10^(-19)) = 0.625xx10^(-19)` Note that one coulomb is too big a unit of charge.

Discussion

864.	An object has an excess charge of `(-1.92xx10^(10-7)) C`. How many excess electrons does it have ?
Answer» Here, excess charge `q = (-1.92xx10^(-17))C` Charge on one electron `e =(-1.6xx10^(-9)) C`. No. of excess electrons reponsible for this excess charge. `n = (q)/(e) = (1.92xx10^(-18))/(1.6xx10^(-19)) = 120` electrons

Discussion

865.	A plane area of `100cm^(2)` is placed in uniform electric field of `100N//C` such that the angle between area vector and electric field is `60^(@)`. The electric flux over the surface isA. `1Nm^(2)//C`B. `2Nm^(2)//C^(2)`C. `3Nm^(2)//C^(2)`D. `0.5Nm^(2)//C`
Answer» Correct Answer - D `phi=dsEcostheta` `=100xx10^(-4)xx100xxcos60` `=0.5Nm^(2)//C`

Discussion

866.	A point charge of `10^(-7)`C is situated at the centre of a cube of side 1m. Calculate the electric flux through its surface.A. `113xx10^(4)Nm^(2)//C`B. `11.3xx10^(4)Nm^(2)//C`C. `1.13xx10^(4)Nm^(2)//C`D. `22xx10^(4)Nm^(2)//C`
Answer» Correct Answer - C `phi=q/in_(0)=10^(-7)/(8.85xx10^(-12))=1.13xx10^(4)Nm^(2)//C`

Discussion

867.	Two capacitors of `3 pF` and `6pF` are connected in series and a potential difference of `5000 V` is applied across the combination. They are then disconnected and reconnected in parallel. The potential between the plates isA. 2250 VB. 1111 VC. `2.25xx10^(6)V`D. `1.1xx10^(6)V`
Answer» Correct Answer - B `Q=CsV=((C_(1)C_(2))/(C_(1)+C_(2)))V=10^(-8)C` In parallel, `V=Q/(C_(1)+C_(2))=10^(-8)/(9xx10^(-12))=1111V`

Discussion

868.	Three plates `A,B` and `C` each of area `0.1m^(2)` are separated by `0.885 mm` from each other as shown in the figure. A `10 V` battery is used to charge the system. The enegry stored in the system is A. `1 muJ`B. `10^(-1) muJ`C. `10^(-2)muJ`D. `10^(-3) muJ`
Answer» Correct Answer - B

Discussion

869.	A gang capacitor is formed by interlocking a number of plates as shown in figure. The distance between the consecutive places is 0.885 cm and the overlapping area of the plates is `5cm^(2).` The capacity of the unit is A. 1.06 pFB. 4 pFC. 6.36 pFD. 12.72 pF
Answer» Correct Answer - B The given arrangement of nine plates is equivalent to the paralllel combination of 8 capacitors. The capacity of each capacitor, `C=(epsilon_(0)A)/(d)` `=(8.854xx10^(-12)xx5xx10^(-4))/(0.885xx10^(-2))` `=0.5pF` Hence, the capacity of 8 capacitors `=8C=8xx0.5=4pF`

Discussion

870.	Two similar helium-filled spherical balloons tied to a 5g weight with strings and each carrying a charge q floats in equilibrium as shown in figure`-1.457`. Find (a) the magnitude of q, assuming that the charge on each balloon acts as ifit were concentrated at the centre and (b) the volume of each balloon. Neglect weight of the unfilled balloons and take density ofair `1.29 kg//m^(3)` and the density of helium in the balloons `0.2 kg//m^(3):`
Answer» Correct Answer - `(a)0.55muC,(b)2.294xx10^(-3)m^(3)`

Discussion

871.	In defining electric field due to a point charge, the test charge, the test charge has to be vanishingly small. How this condition can be justified, when we know that charge less than of electron or a proton is not possible.
Answer» This is true that charge less than electron or proton is not possible but in macrosopic situations, source charge is much larger than charge on electron or proton, so the limit `q_(0) rarr 0` for the test charge is justified.

Discussion

872.	When does a charged circular loop behave as a point charge.
Answer» A charged circular loop behaves as a point charge, when the observation point on its axis is at distance, which is very large compared to the radius of the circular loop.[For details, refer to Art.]

Discussion

873.	Why do the electric field lines never cross each other ?
Answer» At the point of intersection, there will be two directions of electric field, which is not possible.

Discussion

874.	Why are lighting stroms so dangerous ?
Answer» During lighting stroms, electric field develop is on the verge of causing electrical breakdown in the surrounding air. Therefore, lighting stroms are dangerous for the following reasons : (i) if lighting strikes us or something we are touching, it produces a fatal charge flow in our body. (ii) If lighting strikes any object near us, a proton of charge flow may jump to us through the air. (iii) if lighting strikes the ground near us. part of charge flow along the ground can be diverted through our body. (iv) Sometimes, negatively charged base of an overhead cloud results in the movement of some of conduction electrons in our body into the ground, leaving us highly positively charged. This would produce what is called an upward streamer, which is dangerous because resulting ioization of molecules in air sets free, tremendous number of electrons from rhose molecules.

Discussion

875.	In a uniform electric field ,A. all points are at the same potentialB. no two points can have the same potentialC. pairs of points separated by the same distance must have the same difference in potentialD. none of the above
Answer» Correct Answer - D

Discussion

876.	The electric field and the electric potential at a point are E and V respectively.A. If `V=0, E` must be zeroB. If `V!=0,E` cannot be zeroC. If `E!=0,V` cannot be zero.D. None of the these
Answer» Correct Answer - A::B::D

Discussion

877.	A particle `A` of mass `m` and charge `Q` moves directly towards a fixed particle `B`, which has charge `Q`. The speed of `A` is a `v` when it is far away from `B`. The minimum separtion between the particles is not proportional toA. `Q^(2)`B. `1/(v^(2))`C. `1/v`D. `1/m`
Answer» Correct Answer - A::C::D

Discussion

878.	Units of electric flux areA. `("N-m"^(2))/(C)`B. `(N)/(C-m^(2))`C. Volt-mD. `"Volt-m"^(3)`
Answer» Correct Answer - A::C

Discussion

879.	Two point charge `q_(1)=2muC` and `q_(2)=1muC` are placed at distance `b=1` and `a=2cm` from the origin on the `y` and `x` axes as shown in figure .The electric field vector at point `(a),(b)` will subtend on angle `theta` with the "x-axis" given by
Answer» Correct Answer - 2

Discussion

880.	Two identical charges are placed at the two corners of an equilateral triangle. The potential energy of the system is U. The work done in bringing an identical charge from infinity to the third vertex is
Answer» Correct Answer - 2

Discussion

881.	Assertion : Half of the ring is uniformly positively charged and other half uniformly negatively charged. Then, electric field is zero at centre. Then , electric field is zero at centre. Reason : At the centre of uniformly charged ring, electric field is zero.A. If both Assertion and Reason are correct and Reason is the correct explanation of AssertionB. If both Assertion and Reason are correct but Reason is not the correct explanation of AssertionC. If Assertion is true but Reason is falseD. If Assertion is false but Reason is true
Answer» Correct Answer - D

Discussion

882.	The electric potential decreases uniformly from `100 V` to `50 V` as one moves along the x-axis from `x = 0` to `x = 5 m`. The electric field at `x = 2 m` must be equal to `10 V//m`. Is this statement true or false.
Answer» `(delV)/(delx)=(-50)/5=-10V//m` Now `\|E\|=sqrt(((delV)/(delx))^2+((delV)/(dely))^2+((delV)/(delz))^2)` now information is given about `(delV)/(dely) and (delV)/(delz)`. Hence ` `\|E\|ge\|(delV)/(delx)\| or \|E\|ge10V/m`

Discussion

883.	Two parallel plate air capacitors have their plate areas `100 and 500 cm^(2)` respectively. If they have the same charge and potential and the distance between the plates of the first capacitor of 0.5 mm, what is the distance between the plates of second capacitor ?A. 0.25 cmB. 0.52 cmC. 0.75 cmD. 1 cm
Answer» Correct Answer - A Let `A_(1) and d_(1)` be the area of plates and distance between the plates of first capacitor, `A_(2) and d_(2)` be corresponding values in case of second capacitor. If `C_(1) and C_(2)` are the capacitances of two capacitors, then `C_(1)=(epsilon_(0)A_(1))/(d_(1)) and C_(2)=(epsilon_(0)A_(2))/(d_(2))` We know,`" "C=(q)/(V)` Since, the two capacitors have same charge and potential, their capacitance must be equal i.e. `C_(1)=C_(2)` `"or "(epsilon_(0)A_(1))/(d_(1))=(epsilon_(0)A_(2))/(d_(2)) or d_(2)=(A_(2))/(A_(1))d_(1)` Here, `A_(1)=100cm^(2), a+(2)=500cm^(2) and d_(1)=0.5mm = 0.05 cm` `therefore" "d_(2)=(500xx0.05)/(100)=0.25cm`

Discussion

884.	Two parallel plate air capacitors have their plate areas `100 and 500 cm^(2)` respectively. If they have the same charge and potential and the distance between the plates of the first capacitor of 0.5 mm, what is the distance between the plates of second capacitor ?
Answer» Here, two parallel plate capaictors have same charge q and same potential V, so they have equal capacitances as `C = q//V`, `C_(1) = C_(2)` `(in_(0) A_(1))/(d_(1)) = (in_(0) A_(2))/(d_(2))` or `d_(2) = (A_(2))/(A_(1))d_(1)` Now `A_(1) = 100 cm^(2), A_(2) = 500 cm^(2)`, `d_(1) = 0.5 mm = 0.5cm` `:. d_(2) = (500xx0.05)/(100) = 0.25 cm = 2.5 mm`

Discussion

885.	Two plates are `2cm` apart, a potential difference of `10` volt is applied between them, the electric field between the plates isA. `400N//C`B. `600N//C`C. `1000N//C`D. `800N//C`
Answer» Correct Answer - C `E=V/d=10/10^(-2)=1000N//C`

Discussion

886.	A particle of mass 40 mg and carrying a charge `5 xx 10^(-9) C` is moving directly towards a fixed positive point charge on magnitude `10^(-8) C`. When it is at a distance of 10 cm from the fixed positive point charge it has a velocity of `50 cm s^(-1)` at what distance from the fixed point charge will the particle come momentarily to rest ? Is the acceleration constant during motion?
Answer» If the particle comes to rest momentarily at a distance r from the fixed charge, then from conservation of energy, we have ? `1/2 m u^(2) +1/(4pi epsi_(0)) (Qq)/a=1/(4pi epsi_(0)) (Qq)/r` Substituting the given data, we get : `1/2xx40xx10^(-6)xx1/2xx1/2=9xx10^(9)xx5xx10^(-8)xx10^(-9) [1/r-10]` or, `1/r-10=(5xx10^(-6))/(9xx5xx10^(-8))=100/9 implies" "1/r=190/9" "implies" "r=9/190 m` or, i.e. `r=4.7xx10^(-2)m`. As here, `F=1/(4pi epsi_(0)) (Qq)/r^(2)` So, acc. `=F/m prop 1/r^(2)` i.e., Acceleration is not constant during the motion.

Discussion

887.	Figure shown an arrangement of three points charges. The total potential energy of this arrangement zero. The ratio `(q)/(Q)` is :
Answer» `U_("sys")=1/(4pi epsi_(0)) [(-qQ)/r+((+q)(+q))/(2r)+(Q(-q))/r]=0` `-Q+q/2-Q=0` or `2Q=q/2` or `q/Q=4/1`.

Discussion

888.	When two concentric shells are connected by a thin conducting wire, whole of the charge of inner shell transfers to the outer shell and potential difference between them becomes zero. Surface charge densities of two thin concentric spherical shells are `sigma` and `-sigma` respectively. Their radii are R and `2R`. Now they are connected by a thin wire. Suppose electric field at a distance `r (gt 2R)` was `E_(1)` before connecting the two shells and `E_(2)` after connecting the two shells, then `\|E_(2)/E_(1)\|` is :-A. zeroB. 1C. 2D. `(1)/(2)`
Answer» Correct Answer - B

Discussion

889.	When two concentric shells are connected by a thin conducting wire, whole of the charge of inner shell transfers to the outer shell and potential difference between them becomes zero. Surface charge densities of two thin concentric spherical shells are `sigma` and `-sigma` respectively. Their radii are R and `2R`. Now they are connected by a thin wire. Potential on either of the shells will be :-A. `-(3 sigma R)/(2 epsi_(0))`B. `(2 sigma R)/( epsi_(0))`C. `- (sigma R)/(2 epsi_(0))`D. zero
Answer» Correct Answer - A

Discussion

890.	An electron experiences a force equal to its weight, when placed in an electric field. The intensity of the field will beA. `4.36xx10^(-11)N//C`B. `5.573xx10^(-11)N//C`C. `6.67xx10^(-11)N//C`D. `9.86xx10^(-11)N//C`
Answer» Correct Answer - B `F=mg=eE` `therefore" "E=(mg)/e=(9.1xx10^(-31)xx9.8)/(1.6xx10^(-19))` `=5.573xx10^(-11)N//C`

Discussion

891.	A force of 0.01 N is exerted on a charge of 1.2 x 10-5 G at a certain point. The electric field at that point is(a) 5.3 x 104 NC-1(b) 8.3 x 10-4 NC-1 (c) 5.3 x 102 NC-1 (d) 8.3 x 104 NC-1
Answer» (d) 8.3 x 10⁴NC^-1 Hint: E =\(\frac {F}{q}\) = \(\frac {0.01}{1.2 \times 10^{-5}}\) = 8.3 x 10² NC^-1

891.

A force of 0.01 N is exerted on a charge of 1.2 x 10-5 G at a certain point. The electric field at that point is(a) 5.3 x 104 NC-1(b) 8.3 x 10-4 NC-1 (c) 5.3 x 102 NC-1 (d) 8.3 x 104 NC-1

Answer»

(d) 8.3 x 10⁴NC^-1

Hint:

E =\(\frac {F}{q}\) = \(\frac {0.01}{1.2 \times 10^{-5}}\) = 8.3 x 10² NC^-1

Discussion

892.	A charge of `20 muC` produces an electric field. Two points are 10 cm and 5 cm from this charge. Find the values of potentials at these points and calculate work done to take an electron from one point to the other.
Answer» Correct Answer - 1.8xx10^(6)V, 3.6xx10^(6) V, 2.88xx10^(-13)J` Here, `q = 20 muC = 20xx10^(-6)C`. If A and B are two points at distances `r_(1) = 10 cm` `= 0.1 m and r_(2) = 5cm = 0.05m` then `V_(A) = (q)/(4pi in_(0) r_(1)) = (20xx10^(-6)xx9xx10^(9))/(0.1)` `= 1.8xx10^(6) V` `V_(B) = (q)/(4pi in_(0) r_(2)) = (20xx10^(-6)xx9xx10^(9))/(0.05)` `= 3.6xx10^(6) V` `W_(AB) = (V_(B) - V_(A))e` `= (3.6xx10^(6) - 1.8xx10^(6))xx1.6xx10^(-19)` `= 2.88xx10^(-13) J`

Discussion

893.	An electric dipole moment ` vec P = ( 2. 0 hat I + 3 . 0 hat j) mu C m` is placed in a uniform electric field ` vec E = (3 hat I + 2 . 0hat k ) xx 10^5 N C^(-1)`.A. The torque that E exerts in p is `(0.6 hat(i)-0.4 hat(j)-0.9 hat(k))Nm`B. The potential energy of the dipole is `-0.6 J`C. The potential energy of the dipole is 0.6 JD. If the dipole is rotated in the electric field, the maximum potential energy of the dipole is 1.3 J
Answer» Correct Answer - A::B::D

Discussion

894.	A particle of mass m and charge q is fastened to one end of a string of length. The other end of the string is fixed to the point O. The whole sytem liles on as frictionless horizontal plane. Initially, the mass is at rest at A. A uniform electric field in the direction shown in then switfched on. Then A. the speed of the particle when it reaches B is `sqrt((2qEl)/(m))`B. the speed of the particle when it reaches B is `sqrt((qEl)/(m))`C. the tension in the string when particle reaches at B is 2qED. the tension in the string when the particle reaches at B is qE
Answer» Correct Answer - B::C

Discussion

895.	Match the following two columns.
Answer» Correct Answer - A::B::C::D

Discussion

896.	Four metallic plates are charged as shown in figure. Now, match the following two columns. `I overset(sigma)(\|)Iioverset(-2 sigma)(\|)IIIoverset(sigma)(\|)IV`
Answer» Correct Answer - A::B::C::D

Discussion

897.	A diople consisting of an electron and a proton separated by a distance of `4xx10^(-10)` m is situated in an electric field of intensity `3xx10^(5) NC^(-1)` at an angle of `30^(@)` with the field. Calculate the diople moment and the torque acting on it. Charge e on an electron `= 1*6xx10^(-19) C.`
Answer» Here, `q = 16xx10^(-19) C,` `2a = 4xx10^(-10) m, E = 3xx10^(5) NC^(-1), theta = 30^(@)` `p = qxx2a = 1.6xx10^(-19)xx4xx10^(-10) ` `= 64xx10^(-29) Cm` `tau = pE sin theta = 644xx10^(-29)xx3xx10^(5)xxsin 30^(@)` `= 96xx10^(-24) Nm`

Discussion

898.	Electric field intensity at a point B due to a point charge Q kept at a point charge Q kept at point A is `24 NC^(-1)`, and electric potential at B due to the same charge is `12 JC^(-1)`. Calculate the distance AB and magnitude of charge.
Answer» Here, `E = (Q)/(4pi in_(0) r^(2)) = 24 NC^(-1)`, and `V = (Q)/(4pi in_(0) r) = 12 JC^(-1)` Dividing, we get `(V)/(E) = r = (12)/(24) = 05m = AB` From `V = (Q)/(4pi in_(0) r) , Q = 4pi in_(0) r xx V` `Q = (1)/(9xx10^(9)) xx 05xx12 = 0*667 xx 10^(-9) C`

Discussion

899.	Two metallic spheres of radii `R and 2 R` are charged so that both of these have same surface charge density, `sigma` . If they are connected to each other with a conducting wire, in which direction will the charge flow and why ?
Answer» Let `R_(1) = R, R_(2) = 2R`. If `Q_(1) and Q_(2)` are the respective charges, then as `sigma = (Q_(1))/(4pi R_(1)^(2)) = (Q_(2))/(4pi R_(2)^(2))` `:. (Q_(1))/(Q_(2)) = (R_(1)^(2))/(R_(2)^(2)) = ((R )/(2R))^(2) = (1)/(4)` `As V_(1) = (Q_(1))/(4pi in_(0) R_(1)) , V_(2) = (Q_(2))/(4pi in_(0) R_(2))` `:. (V_(1))/(V_(2)) = (Q_(1))/(Q_(2)) , (R_(2))/(R_(1)) = (1)/(4) xx (2)/(1) = (1)/(2)` Clearly, `V_(2) gt V_(1)`. Hence charge flows from sphere of radius `2 R` to sphere of radius R.

Discussion

900.	The electric intensity of outside a charged sphere of radius R at a distance `r (r gt R)` isA. `(sigma R^(2))/(epsilon_(0)r^(2))`B. `(sigma r^(2))/(epsilon_(0)R^(2))`C. `(sigma r)/(epsilon_(0)R)`D. `(sigma R)/(epsilon_(0)r)`
Answer» Correct Answer - A The electric intensity outside a charged sphere, `E=(sigmaR^(2))/(epsilon_(0)r^(2))`

Discussion

Explore topic-wise InterviewSolutions in .

Four point charge `q, - q, 2Q` and Q are placed in order at the corners A, B, C and D of a square. If the field at the midpoint of CD is zero then the value of `q//Q` is `(5 sqrt5)/(x)`. Find the value of x.

If a positive charge is shifted from a low - potential region to a high- potential region, the electric potential energyA. IncreasesB. DecreasesC. May increase or decreaseD. Remains constant

A hollow charged metal sphere has radius `r`. If the potential difference between its surface and a point at a distance `3r` from the centre is V, then electric field intensity at a distance `3r` isA. V/6rB. V/4rC. V/3rD. V/2r

A hollow metal sphere of radius 5 cms is charged such that the potential on its surface is 10 volts. The potential at the centre of the sphere isA. ZeroB. 10 voltC. Same as at a point 5 cm away from the surfaceD. Same as at a point 25 cm away from the centre

A conducting sphere of radius R is charged to a potential of V volts. Then the electric field at a distance `r ( gt R)` from the centre of the sphere would beA. `(V)/(r)`B. `(R^(2)V)/(r^(3))`C. `(RV)/(r^(2))`D. `(rV)/(R^(2))`

In going from the surface of a charged conducting sphere towards the centre of the sphere the electric fieldA. increasesB. decreasesC. remains the same as on the surfaceD. remains zero at every place

An electron and a proton are freely situated in an electric field. Will the electric forces on them be equal? Will their acceleration be equal? Explain with reason.A. zeroB. unityC. ratio of the mass of proton and electronD. ratio of the mass of electron and proton

A metal sphere has a charge of `-6.5 muC`. When `5xx10^(13)` electrons are removed from the sphere, what would be the net charge on it?

If a body gives out `10^(9)` electrons every second, how much time required to get a total charge of `1 C` from it ?

Which is bigger, a coulomb or charge on an electron ? How many electronic charges from one coulomb of charge ?

An object has an excess charge of `(-1.92xx10^(10-7)) C`. How many excess electrons does it have ?

A plane area of `100cm^(2)` is placed in uniform electric field of `100N//C` such that the angle between area vector and electric field is `60^(@)`. The electric flux over the surface isA. `1Nm^(2)//C`B. `2Nm^(2)//C^(2)`C. `3Nm^(2)//C^(2)`D. `0.5Nm^(2)//C`

A point charge of `10^(-7)`C is situated at the centre of a cube of side 1m. Calculate the electric flux through its surface.A. `113xx10^(4)Nm^(2)//C`B. `11.3xx10^(4)Nm^(2)//C`C. `1.13xx10^(4)Nm^(2)//C`D. `22xx10^(4)Nm^(2)//C`

Two capacitors of `3 pF` and `6pF` are connected in series and a potential difference of `5000 V` is applied across the combination. They are then disconnected and reconnected in parallel. The potential between the plates isA. 2250 VB. 1111 VC. `2.25xx10^(6)V`D. `1.1xx10^(6)V`

Three plates `A,B` and `C` each of area `0.1m^(2)` are separated by `0.885 mm` from each other as shown in the figure. A `10 V` battery is used to charge the system. The enegry stored in the system is A. `1 muJ`B. `10^(-1) muJ`C. `10^(-2)muJ`D. `10^(-3) muJ`

A gang capacitor is formed by interlocking a number of plates as shown in figure. The distance between the consecutive places is 0.885 cm and the overlapping area of the plates is `5cm^(2).` The capacity of the unit is A. 1.06 pFB. 4 pFC. 6.36 pFD. 12.72 pF

In defining electric field due to a point charge, the test charge, the test charge has to be vanishingly small. How this condition can be justified, when we know that charge less than of electron or a proton is not possible.

When does a charged circular loop behave as a point charge.

Why do the electric field lines never cross each other ?

Why are lighting stroms so dangerous ?

In a uniform electric field ,A. all points are at the same potentialB. no two points can have the same potentialC. pairs of points separated by the same distance must have the same difference in potentialD. none of the above

The electric field and the electric potential at a point are E and V respectively.A. If `V=0, E` must be zeroB. If `V!=0,E` cannot be zeroC. If `E!=0,V` cannot be zero.D. None of the these

A particle `A` of mass `m` and charge `Q` moves directly towards a fixed particle `B`, which has charge `Q`. The speed of `A` is a `v` when it is far away from `B`. The minimum separtion between the particles is not proportional toA. `Q^(2)`B. `1/(v^(2))`C. `1/v`D. `1/m`

Units of electric flux areA. `("N-m"^(2))/(C)`B. `(N)/(C-m^(2))`C. Volt-mD. `"Volt-m"^(3)`

Two point charge `q_(1)=2muC` and `q_(2)=1muC` are placed at distance `b=1` and `a=2cm` from the origin on the `y` and `x` axes as shown in figure .The electric field vector at point `(a),(b)` will subtend on angle `theta` with the "x-axis" given by

Two identical charges are placed at the two corners of an equilateral triangle. The potential energy of the system is U. The work done in bringing an identical charge from infinity to the third vertex is

The electric potential decreases uniformly from `100 V` to `50 V` as one moves along the x-axis from `x = 0` to `x = 5 m`. The electric field at `x = 2 m` must be equal to `10 V//m`. Is this statement true or false.

Two parallel plate air capacitors have their plate areas `100 and 500 cm^(2)` respectively. If they have the same charge and potential and the distance between the plates of the first capacitor of 0.5 mm, what is the distance between the plates of second capacitor ?

Two plates are `2cm` apart, a potential difference of `10` volt is applied between them, the electric field between the plates isA. `400N//C`B. `600N//C`C. `1000N//C`D. `800N//C`

Figure shown an arrangement of three points charges. The total potential energy of this arrangement zero. The ratio `(q)/(Q)` is :

An electron experiences a force equal to its weight, when placed in an electric field. The intensity of the field will beA. `4.36xx10^(-11)N//C`B. `5.573xx10^(-11)N//C`C. `6.67xx10^(-11)N//C`D. `9.86xx10^(-11)N//C`

A force of 0.01 N is exerted on a charge of 1.2 x 10-5 G at a certain point. The electric field at that point is(a) 5.3 x 104 NC-1(b) 8.3 x 10-4 NC-1 (c) 5.3 x 102 NC-1 (d) 8.3 x 104 NC-1

A charge of `20 muC` produces an electric field. Two points are 10 cm and 5 cm from this charge. Find the values of potentials at these points and calculate work done to take an electron from one point to the other.

Match the following two columns.

Four metallic plates are charged as shown in figure. Now, match the following two columns. `I overset(sigma)(|)Iioverset(-2 sigma)(|)IIIoverset(sigma)(|)IV`

A diople consisting of an electron and a proton separated by a distance of `4xx10^(-10)` m is situated in an electric field of intensity `3xx10^(5) NC^(-1)` at an angle of `30^(@)` with the field. Calculate the diople moment and the torque acting on it. Charge e on an electron `= 1*6xx10^(-19) C.`

Electric field intensity at a point B due to a point charge Q kept at a point charge Q kept at point A is `24 NC^(-1)`, and electric potential at B due to the same charge is `12 JC^(-1)`. Calculate the distance AB and magnitude of charge.

Two metallic spheres of radii `R and 2 R` are charged so that both of these have same surface charge density, `sigma` . If they are connected to each other with a conducting wire, in which direction will the charge flow and why ?

The electric intensity of outside a charged sphere of radius R at a distance `r (r gt R)` isA. `(sigma R^(2))/(epsilon_(0)r^(2))`B. `(sigma r^(2))/(epsilon_(0)R^(2))`C. `(sigma r)/(epsilon_(0)R)`D. `(sigma R)/(epsilon_(0)r)`