1638 + Interview Questions in ELECTROSTATICS IN GENERAL AWARENESS Page 12 InterviewSolution

551.	What is corona discharge?
Answer» The electric field near the edge is very high and it ionizes the surrounding air. The positive ions are repelled at the sharp edge and negative ions are attracted towards the sharper edge. This reduces the total charge of the conductor near the sharp edge. This is called action at points or corona discharge.

Discussion

552.	Charge on `alpha-`particle isA. `4.8 xx 10^(-19)C`B. `1.6 xx 10^(-19)C`C. `3.2 xx 10^(-19)C`D. `6.4 xx 100^(-19)C`
Answer» Correct Answer - C

Discussion

553.	A body has `-80` micro coulomb of charge. Number of additional electrons in it will beA. `8 xx 10^(-5)`B. `80 xx 10^(-17)`C. `5 xx 10^(14)`D. `1.28 xx 10^(-17)`
Answer» Correct Answer - C

Discussion

554.	Total electric fulx coming out of a unit positive charge put in air is(a) ε0(b) ε0-1 (c) (4πε0 )-1(d) 4πε0
Answer» Correct answer is (b) ε₀^-1

Discussion

555.	A cube of side b has a charge q at each of its vertices. The electric field due to this charge distribution at the centre of the cube is(a) \(\frac {q}{b^2}\)(b) \(\frac {q}{2b^2}\) (c) \(\frac {32q}{b^2}\) (d) Zero
Answer» (d) zero Thereis an equal charge at diagonally opposite comer. The fields due the these at the centre cancel out. Therefore, the net field at the centre is zero.

555.

A cube of side b has a charge q at each of its vertices. The electric field due to this charge distribution at the centre of the cube is(a) \(\frac {q}{b^2}\)(b) \(\frac {q}{2b^2}\) (c) \(\frac {32q}{b^2}\) (d) Zero

Answer»

(d) zero

Thereis an equal charge at diagonally opposite comer. The fields due the these at the centre cancel out. Therefore, the net field at the centre is zero.

Discussion

556.	Electron volt (eV) is a unit of (a) energy (b) potential (c) current (d) charge
Answer» Correct answer is (a) energy

Discussion

557.	L shaped rod has equal and opposite charge `(+- Q)` spread along its both arms (see figure). (a) What is direction of electric field at point P? (b) Write electric potential at P.
Answer» Correct Answer - (a). Prallel to `vec(AB)` (b). Zero

Discussion

558.	Fig.1 shows the variation of electric potential V with `1//r`, where r is the distance from the two charges `Q_(1) and Q_(2)`. Determine (i) signs of two charges `Q_(1) and Q_(2)` (ii) Which of the two charges has a larger magnitude ? Justify.
Answer» Electric potential due to a point charge Q at a point distance r from the charge is `V = (Q)/(4pi in_(0) r)` V is `+` only when Q is `+`. Therefore from fig. `Q_(1)` is `+ Q_(2)` is negative . For a given value of r, we find from Fig that `V_(2) gt V_(1)` `Q_(2) gt Q_(1)`

Discussion

559.	A condenser having a capacity of `50muF` is charged to a potential of 200 V. If the area of each plate of the condenser is `10cm^(2)` and the distance between the plates is 0.1 mm. The energy per unit volume of the field between the plates isA. `10^(6)J//m^(3)`B. `10^(-6)J//m^(3)`C. `10^(7)J//m^(3)`D. `10^(-7)J//m^(3)`
Answer» Correct Answer - C `u=(1/2CV^(2))/(A*d)=(CV^(2))/(2Ad)` `=(50xx10^(-6)xx200xx200)/(2xx10xx10^(-4)xx0.1xx10^(-3))=10^(7)J//m^(3).`

Discussion

560.	The area of each plate of parallel plate condenser is `20cm^(2)` and distance them is 2mm. It stores the energy if 5J. The energy density of electric field between its plates isA. `250xx10^(6)J//m^(3)`B. `1.25xx10^(6)J//m^(3)`C. `2xx10^(6)J//m^(3)`D. `4xx10^(6)J//m^(3)`
Answer» Correct Answer - B `A=20Cm^(2),d=2mm,U=5J,u=?` `u=("energy")/("volume")=U/(A.d)=5/(20xx10^(-4)xx2xx10^(-3))` `=1.25xx10^(6)J//m^(3)`

Discussion

561.	Two insulated metal spheres of raddi 10 cm and 15 cm charged to a potential of 150 V and 100 V respectively, are connected by means of a metallic wire. What is the charge on the first sphere?A. 2 esuB. 4 esuC. 6 esuD. 8 esu
Answer» Correct Answer - B Here, `r_(1)=10cm, r_(2)=15cm, V_(1)=150V, V_(2)=100V` Common potential, `V=(C_(1)V_(1)+C_(2)V_(2))/(C_(1)+C_(2))=(4pi epsilon_(0)(r_(1)V_(1)+r_(2)V_(2)))/(4pi epsilon_(0)(r_(1)+r_(2))=120V` `therefore" "q_(1)=C_(1)V=4pi epsilon_(0)r_(1)V=(10^(-1))/(9xx10^(9))xx120C` `=(12)/(9xx10^(9))xx3xx10^(9)"esu = 4 esu"`

Discussion

562.	The radii of the inner and outer spheres of a condenser are 9 cm and 10 m respectively. If the dielectric constant of the medium between the two sphere is 6 and charge on the inner sphere is `18xx10^(-9)C`, then the potential of inner sphere will be, if the other sphere is earthedA. 180 VB. 30 VC. 18 VD. 90 V
Answer» Correct Answer - B Given, system is a spherical capacitor so, capacitance of system, `C=K xx4piepsilon_(0)[(r_(1)r_(2))/(r_(2)-r_(1))]` `=(6)/(9xx10^(9))[(9xx10)/(1)]xx10^(-2)=6xx10^(-10)F` Now, potential of inner sphere will be equal to potential difference of the capacitor. So, `V=(q)/(C)=(18xx10^(-9))/(6xx10^(-2))=30V`

Discussion

563.	In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10–3 m2 and the separation between the plates is 3 mm. (i) Calculate the capacitance of the capacitor. (ii) If this capacitor is connected to 100 V supply, what would be the charge on each plate? (iii) How would charge on the plates be affected, if a 3 mm thick mica sheet of K = 6 is inserted between the plates while the voltage supply remains connected?
Answer» Here, A = 6 × 10^–3 m², d = 3 mm = 3 × 10^–3 m (i) Capacitance, C = ε₀A/d = (8.85 x 10^-12 x 6 x 10^-3/3 x 10^-3) = 17.7 x 10^-12 F (ii) Charge, Q = CV = 17.7 x 10^-12 x 100C = 17.7 x 10^-10C (iii) New charge, Q’ = KQ =6 x 17.7 x 10^-10 C =106.2 x10^-10 C

563.

In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10–3 m2 and the separation between the plates is 3 mm. (i) Calculate the capacitance of the capacitor. (ii) If this capacitor is connected to 100 V supply, what would be the charge on each plate? (iii) How would charge on the plates be affected, if a 3 mm thick mica sheet of K = 6 is inserted between the plates while the voltage supply remains connected?

Answer»

Here, A = 6 × 10^–3 m², d = 3 mm = 3 × 10^–3 m

(i) Capacitance, C = ε₀A/d = (8.85 x 10^-12 x 6 x 10^-3/3 x 10^-3) = 17.7 x 10^-12 F

(ii) Charge, Q = CV = 17.7 x 10^-12 x 100C = 17.7 x 10^-10C

(iii) New charge, Q’ = KQ =6 x 17.7 x 10^-10 C =106.2 x10^-10 C

Discussion

564.	In a parallel plate capacitor with air between the plates, each plate has an area of 5 × 103 m2 and the separation between the plates is 2.5 mm. (i) Calculate the capacitance of the capacitor. (ii) If this capacitor is connected to 100 V supply, what would be the charge on each plate? (iii) How would charge on the plates be affected, if a 2.5 mm thick mica sheet of K = 8 is inserted between the plates while the voltage supply remains connected?
Answer» Here, A = 5 × 10^–3 m², d = 2.5 mm = 2.5 × 10^–3 m (i) Capacitance, C = ε₀A/d = (8.85 x 10^-12 x 5 x 10^-3/2.5 x 10^-3) = 17.7 x 10^-12 F (ii) Charge, Q = CV = 17.7 x 10^-12 x 100 C = 17.7 x 10^-10 C (iii) New charge, Q’ = KQ = 8 x 17.7 x 10^-10C = 141.6 x 10^-10 C

564.

In a parallel plate capacitor with air between the plates, each plate has an area of 5 × 103 m2 and the separation between the plates is 2.5 mm. (i) Calculate the capacitance of the capacitor. (ii) If this capacitor is connected to 100 V supply, what would be the charge on each plate? (iii) How would charge on the plates be affected, if a 2.5 mm thick mica sheet of K = 8 is inserted between the plates while the voltage supply remains connected?

Answer»

Here, A = 5 × 10^–3 m², d = 2.5 mm = 2.5 × 10^–3 m

(i) Capacitance, C = ε₀A/d = (8.85 x 10^-12 x 5 x 10^-3/2.5 x 10^-3) = 17.7 x 10^-12 F

(ii) Charge, Q = CV = 17.7 x 10^-12 x 100 C = 17.7 x 10^-10 C

(iii) New charge, Q’ = KQ = 8 x 17.7 x 10^-10C = 141.6 x 10^-10 C

Discussion

565.	Three poistive charges of equal value q are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as inA. (a) B. (b) C. (c) D. (d)
Answer» Correct Answer - C Electric field lines do not form closed loops. Therefore options (a), (b) and (d) are wrong. Option (c) is correct. There is repulison between ismilar charges.

Discussion

566.	If the electric potential of the inner shell is `10 V` and that of the outer shel is `5V`, then the potential at the centre will be A. `10V`B. `5V`C. `15V`D. zero
Answer» Correct Answer - A From centre of the surface of inner shell potential will remain constnt =10 V (given)

Discussion

567.	An electrical charge is aA. scalar quantityB. vector quantityC. vector quantity (radial)D. none of these
Answer» Correct Answer - A

Discussion

568.	A charge Q is kept in the inner cavity and a charge 2 Q is given to the inner shel. A charge 3 Q is given to the outermost shell, as shown in Fig. 1 (a).22 Find the charges at the surfaces A,B and C.
Answer» Due to induction, `- Q` charge is induced on the inner surface A of inner shell and `+ Q` charge is induced on the outer surface B of inner shell. Thus, charge on surface `A = -Q`. Now charge on surface `B = 2Q + Q = 3Q` Due to induction, `-3Q` charge is induced on the inner surface of outer shell C and `+3Q` charge is induced on the outer surface of outer shell C. Thus total charge on surface `C = 3 Q + 3 Q = 6Q`.

Discussion

569.	The electric field strength depends only on the x and y coordinates according to the law E = `(a(xhati+ y hatj))/(x^(2) + y^(2))` , where a is a constant `hati` and `hatj` are unit vectors of the x and y axes . Find the potential difference between x = 1 and x = 5 :
Answer» Correct Answer - [`-a "ln"(5)`]

Discussion

570.	A parallel plate capacitor of area A, plate separation d and capacitance C is filled with three different dielectric materials having dielectric constants `k_1`, `k_2` and `k_3` as shown. If a isngle dielectric material is to be used to have the same capacitance C in this capacitor, then its dielectic constant k is given by A. `1/(K_(1)+K_(2))+1/(2K_(3))`B. `1/(K_(1)+K_(2))-1/(2K_(3))`C. `1/(K_(1)-K_(2))+1/(2K_(3))`D. `2/(K_(1)+K_(2))+1/(2K_(3))`
Answer» Correct Answer - A The given capacitor may be supposed to be formed of three component capacitors `C_(1), C_(2) and C_(3)`. Let `K_(1), K_(2) and K_(3)` be dielectric constant of `C_(1), C_(2) and C_(3)` respectively. Condenser `C_(1) and C_(2)` are in parallel. Let `C_(p) = C_(1)+C_(2)`. Now, `C_(p) and C_(3)` are connected in series. There equivalent capacitance is given by `C_(s)`. From figure, `C_(p)=C_(1)+C_(2)` `C_(p)=(AK_(1)in_(0))/(2d/2)+(AK_(2)in_(0))/(2d/2)=(Ain_(0))/d(K_(1)+K_(2))` Now `C_(p) and C_(3)` are in series `1/C_(s)=1/C_(p)+1/C_(3)" "(C_(3)=(2AK_(3)in_(0))/d)` `1/C_(s)=1/((Ain_(0))/d(K_(1)+K_(2)))+1/((2Ain_(0)K_(3))/d)` `1/((AKin_(0))/d)=1/((Ain_(0))/d(K_(1)+K_(2)))+1/((Ain_(0))/d2k_(3))` `therefore" "1/K=1/(K_(1)+K_(2))+1/(2K_(3))`

Discussion

571.	Consider three charged bodies P,Q and R. If P and Q repel each other and P attracts R, what is the nature of force between Q and R ?
Answer» Attractive, because Q and R will carry opposite charges.

Discussion

572.	A negatively charged ebonite rod attracts a suspended ball of straw. Can we infer that the ball is positively charged ?
Answer» No. because the negatively charged rod can attract an uncharged ball due to induction and can also attract positively charged ball, B carrying smaller charge shall acquire some net charge of opposite sign lying closer to A. Hence B will experience some net force of attraction.

Discussion

573.	Define dielectric constant of a medium in terms of force between electric charges.
Answer» The dielectric constant of a medium is the ration of force between two charges placed some distance apart in vacumm to the force between same two charges placed same distance apart in the given medium.

Discussion

574.	The positive and negative names of the charges were given byA. CoulombB. GilbertC. AristotleD. Franklin
Answer» Correct Answer - D

Discussion

575.	Conisder the istuation shown in the figure. The capacitor A has a charge q on it whereas B is unchanged. The charge appearing on the capacitor B a long time after the switch is closed is A. (a) zeroB. (b) `q//2`C. (c) `q`D. (d) 2q
Answer» Correct Answer - A When S is closed, there will be no shifting of negative charge from plate A to B as the charge-q is held by the charge +q. Neither there will be any shifting of charge form B to A.

Discussion

576.	The line of force are alwaysA. perpendicular to the surface of charged bodyB. parallel to the surface of charged bodyC. inclined to the surface of charged bodyD. none of these
Answer» Correct Answer - A

Discussion

577.	The total number of tubes of induction passing normally through the given area is called asA. normal electric inductionB. total normal electric inductionC. electric potentialD. electric power
Answer» Correct Answer - B

Discussion

578.	The properties of electric lines of force, tubes of force and tubes of induction areA. never similarB. approximately similarC. exactly similarD. none of these
Answer» Correct Answer - C

Discussion

579.	Two positive ions , each carrying a charge `q` , are separated by a distance `d`.If `F` is the force of repulsion between the ions , the number of electrons missing from each ion will be (`e` being the charge on an electron)A. `(4 pi in_(0) Fd^(2))/(q^(2))`B. `(4pi in_(0) Fd^(2))/(2)`C. `sqrt((4 pi in_(0) Fe^(2))/(d^(2)))`D. `sqrt((4pi in_(0) Fd^(2))/(e^(2)))`
Answer» Correct Answer - 4 `F = (1)/(4 pi in_(0)) .(q^(2))/(d^(2))` `q = n e = sqrt(4 pi in_(0) d^(2) F)` `n = sqrt((4 pi in_(0) d^(2) F)/( e))` `n`: number of missing electrons.

Discussion

580.	Two positive ions , each carrying a charge `q` , are separated by a distance `d`.If `F` is the force of repulsion between the ions , the number of electrons missing from each ion will be (`e` being the charge on an electron)A. `(4 pi epai_(0)Fd^(2))/(e)`B. `sqrt((4 pi epsi_(0)Fe^(2))/(d^(2)))`C. `sqrt((4 pi epsi_(0)Fd^(2))/(e^(2)))`D. `(4 pi epsi_(0)Fd^(2))/(e^(2))`
Answer» Correct Answer - C

Discussion

581.	Write down the value of obsolute permittivity of free space.
Answer» Absolute permittivity of free space `in_(0) = 8.85xx10^(-12) C^(2) N^(-1) m^(-2).`

Discussion

582.	What is the force of repulsion between two charges of `1C` each, kept `1m` apart in vacumm ?
Answer» `F = (kq_(1) q_(2))/(r^(2)) = (9xx10^(9)xx1xx1xx)/((1)^(2)) = 9xx10^(9) N`

Discussion

583.	The electric lines of force do not passes throughA. metalsB. conductorsC. semiconductorsD. all of these
Answer» Correct Answer - D

Discussion

584.	If the number of condensers are connected in series thenA. charge on each condenser is same and potential is differentB. potential is same but charge is differentC. both charge and potential is sameD. both charge and potential is different
Answer» Correct Answer - A

Discussion

585.	If the number of condensers are connected one after another then this type of combination of condensers isA. parallelB. seriesC. both series and parallelD. neither series nor parallel
Answer» Correct Answer - A

Discussion

586.	In series combination of condensers, potential is distributed inA. proportion to there capacitancesB. inverse proportion to their capacitanceC. does not depend on capacitanceD. can not be predicted
Answer» Correct Answer - B

Discussion

587.	Energy of a charged condenser is given byA. `E=(CV^(2))/2`B. `E=Q^(2)/(2C)`C. `E=(QV)/(2)`D. all of these
Answer» Correct Answer - D

Discussion

588.	Energy of a charged condenser is given byA. `1/2CV^(2)`B. `1/4CV^(2)`C. `1/2CV`D. `1/4CV`
Answer» Correct Answer - A

Discussion

589.	If the number of condensers are connected one after another then this type of combination of condensers isA. condensers in seriesB. condensers in parallelC. condensers in series and parallelD. none of these
Answer» Correct Answer - A

Discussion

590.	A potential difference of 50 V is maintained between the two plates of a parallel plate condenser, separated by 5 mm of air. The energy stored in unit volume of air between the plates of the condenser isA. `4.425xx10^(-4) J//m^(3)`B. `2.425xx10^(-4) J//m^(3)`C. `8.425xx10^(-4) J//m^(3)`D. `6.425xx10^(-4) J//m^(3)`
Answer» Correct Answer - A `u=1/2in_(0)kE^(2)=(in_(0)kV^(2))/(2d^(2))` `=(8.85xx10^(-12)xx1xx2500)/(2xx5xx10^(-3)xx5xx10^(-3))` `=4.425xx10^(-4)J//m^(3)`

Discussion

591.	The amount of energy stored in condenser becomes nine times the initial energy. The new potential of condenser isA. three times the initial potentialB. nine times the initial potentialC. four times the initial potentialD. none of these
Answer» Correct Answer - A

Discussion

592.	If the flux of the electric field through a closed surface is zero , (i) the electric field must be zero everywhere on the surface (ii) the electric field may be zero everywhere on the surface (iii) the charge inside the surface must be zero (iv) the charge in the vicinity of the surface must be zeroA. (i), (ii)B. (ii), (iii)C. (ii), (iv)D. (i), (iii)
Answer» Correct Answer - B

Discussion

593.	A pyramid has four faces, all of them being equilateral triangle of side a. A charge Q is placed at the centre of one of the faces. What is the flux of electric field emerging from any one of the other three faces of the pyramid?
Answer» Correct Answer - `(Q)/(6epsilon_(0))`

Discussion

594.	A point charge is placed very close to an infinite plane. What is flux through the plane?
Answer» Correct Answer - `(q)/(2epsilon_(0))`

Discussion

595.	An ellipsoidal cavity is carved within a perfect conductor. A positive charge q is placed at the centre of the cavity. The points A and B are on the cavity surface as shown in the figure. Then A. Electric field near A in the cavity = electric field near b in the cavityB. Charge density at A = Charge density at BC. Potential at A = Potetial at BD. Total electric field flux through the surface of the cavity is `q//epsi_(0)`.
Answer» Correct Answer - C

Discussion

596.	Figure shown a closed surface which intersects a conducting sphere. If a positive charge is placed at the point P, the flux of the electric field through the closed surface A. will become positiveB. will remain zeroC. will become undefinedD. will become negative
Answer» Correct Answer - A

Discussion

597.	Point charge q s placed at a point on the axis of a square non-conducting surface. The axis is perpendicular to the square surface and is passing through its centre. Flux of electric field throught he square caused due to charged q is `phi`. If the square is given a surface change of uniform density `sigma`, find the force on the square surface due to point charge q.
Answer» Correct Answer - `sigma phi`

Discussion

598.	In a region of space the electric field in the `x`-direction and proportional to `x`i.e., `vec(E )=E_(0)xhat(i)`. Consider an imaginary cubical volume of edge a with its parallel to the axes of coordinates. The charge inside this volume will beA. zeroB. `epsilon_(0)E_(0)a^(3)`C. `1/(epsilon_(0))E_(0)a^(3)`D. `1/6 epsilon_(0)E_(0)a^(2)`
Answer» Correct Answer - B

Discussion

599.	A dipole having dipole moment p is placed in front of a solid uncharged conducting sphere as shown in the diagram. The net potential at point A lying on the surface of the sphere is : A. `(kp cos phi)/r^(2)`B. `(kp cos^(2) phi)/r^(2)`C. zeroD. `(2kp cos^(2) phi)/r^(2)`
Answer» Correct Answer - B

Discussion

600.	If the uniform electric field is `3xx10^(3)hatiNC^(-1)`, then the flux of this field through a square of 10 cm on a side whose plane is parallel to the y-z- plane gt?A. `30Nm^(2)C^(-1)`B. `60Nm^(2)C^(-1)`C. `15Nm^(2)C^(-1)`D. `25Nm^(2)C^(-1)`
Answer» Correct Answer - A Here `E=3xx10^(3)hatiNc^(-1)` Field is along positive direction of X-axis Surface are `S=(10)^(2)cm^(2)=10^(-2)m^(2)` When plane is parallel to YZ - plane, `theta=0^(@)` `phi_(E)=ES cos theta=3xx10^(3)xx10^(-2)cos theta=30Nm^(2)C^(-1)`

Discussion

Explore topic-wise InterviewSolutions in .

What is corona discharge?

Charge on `alpha-`particle isA. `4.8 xx 10^(-19)C`B. `1.6 xx 10^(-19)C`C. `3.2 xx 10^(-19)C`D. `6.4 xx 100^(-19)C`

A body has `-80` micro coulomb of charge. Number of additional electrons in it will beA. `8 xx 10^(-5)`B. `80 xx 10^(-17)`C. `5 xx 10^(14)`D. `1.28 xx 10^(-17)`

Total electric fulx coming out of a unit positive charge put in air is(a) ε0(b) ε0-1 (c) (4πε0 )-1(d) 4πε0

A cube of side b has a charge q at each of its vertices. The electric field due to this charge distribution at the centre of the cube is(a) \(\frac {q}{b^2}\)(b) \(\frac {q}{2b^2}\) (c) \(\frac {32q}{b^2}\) (d) Zero

Electron volt (eV) is a unit of (a) energy (b) potential (c) current (d) charge

L shaped rod has equal and opposite charge `(+- Q)` spread along its both arms (see figure). (a) What is direction of electric field at point P? (b) Write electric potential at P.

Fig.1 shows the variation of electric potential V with `1//r`, where r is the distance from the two charges `Q_(1) and Q_(2)`. Determine (i) signs of two charges `Q_(1) and Q_(2)` (ii) Which of the two charges has a larger magnitude ? Justify.

The area of each plate of parallel plate condenser is `20cm^(2)` and distance them is 2mm. It stores the energy if 5J. The energy density of electric field between its plates isA. `250xx10^(6)J//m^(3)`B. `1.25xx10^(6)J//m^(3)`C. `2xx10^(6)J//m^(3)`D. `4xx10^(6)J//m^(3)`

Two insulated metal spheres of raddi 10 cm and 15 cm charged to a potential of 150 V and 100 V respectively, are connected by means of a metallic wire. What is the charge on the first sphere?A. 2 esuB. 4 esuC. 6 esuD. 8 esu

Three poistive charges of equal value q are placed at the vertices of an equilateral triangle. The resulting lines of force should be sketched as inA. (a) B. (b) C. (c) D. (d)

If the electric potential of the inner shell is `10 V` and that of the outer shel is `5V`, then the potential at the centre will be A. `10V`B. `5V`C. `15V`D. zero

An electrical charge is aA. scalar quantityB. vector quantityC. vector quantity (radial)D. none of these

A charge Q is kept in the inner cavity and a charge 2 Q is given to the inner shel. A charge 3 Q is given to the outermost shell, as shown in Fig. 1 (a).22 Find the charges at the surfaces A,B and C.

The electric field strength depends only on the x and y coordinates according to the law E = `(a(xhati+ y hatj))/(x^(2) + y^(2))` , where a is a constant `hati` and `hatj` are unit vectors of the x and y axes . Find the potential difference between x = 1 and x = 5 :

Consider three charged bodies P,Q and R. If P and Q repel each other and P attracts R, what is the nature of force between Q and R ?

A negatively charged ebonite rod attracts a suspended ball of straw. Can we infer that the ball is positively charged ?

Define dielectric constant of a medium in terms of force between electric charges.

The positive and negative names of the charges were given byA. CoulombB. GilbertC. AristotleD. Franklin

Conisder the istuation shown in the figure. The capacitor A has a charge q on it whereas B is unchanged. The charge appearing on the capacitor B a long time after the switch is closed is A. (a) zeroB. (b) `q//2`C. (c) `q`D. (d) 2q

The line of force are alwaysA. perpendicular to the surface of charged bodyB. parallel to the surface of charged bodyC. inclined to the surface of charged bodyD. none of these

The total number of tubes of induction passing normally through the given area is called asA. normal electric inductionB. total normal electric inductionC. electric potentialD. electric power

The properties of electric lines of force, tubes of force and tubes of induction areA. never similarB. approximately similarC. exactly similarD. none of these

Write down the value of obsolute permittivity of free space.

What is the force of repulsion between two charges of `1C` each, kept `1m` apart in vacumm ?

The electric lines of force do not passes throughA. metalsB. conductorsC. semiconductorsD. all of these

If the number of condensers are connected in series thenA. charge on each condenser is same and potential is differentB. potential is same but charge is differentC. both charge and potential is sameD. both charge and potential is different

If the number of condensers are connected one after another then this type of combination of condensers isA. parallelB. seriesC. both series and parallelD. neither series nor parallel

In series combination of condensers, potential is distributed inA. proportion to there capacitancesB. inverse proportion to their capacitanceC. does not depend on capacitanceD. can not be predicted

Energy of a charged condenser is given byA. `E=(CV^(2))/2`B. `E=Q^(2)/(2C)`C. `E=(QV)/(2)`D. all of these

Energy of a charged condenser is given byA. `1/2CV^(2)`B. `1/4CV^(2)`C. `1/2CV`D. `1/4CV`

If the number of condensers are connected one after another then this type of combination of condensers isA. condensers in seriesB. condensers in parallelC. condensers in series and parallelD. none of these

The amount of energy stored in condenser becomes nine times the initial energy. The new potential of condenser isA. three times the initial potentialB. nine times the initial potentialC. four times the initial potentialD. none of these

A pyramid has four faces, all of them being equilateral triangle of side a. A charge Q is placed at the centre of one of the faces. What is the flux of electric field emerging from any one of the other three faces of the pyramid?

A point charge is placed very close to an infinite plane. What is flux through the plane?

Figure shown a closed surface which intersects a conducting sphere. If a positive charge is placed at the point P, the flux of the electric field through the closed surface A. will become positiveB. will remain zeroC. will become undefinedD. will become negative

A dipole having dipole moment p is placed in front of a solid uncharged conducting sphere as shown in the diagram. The net potential at point A lying on the surface of the sphere is : A. `(kp cos phi)/r^(2)`B. `(kp cos^(2) phi)/r^(2)`C. zeroD. `(2kp cos^(2) phi)/r^(2)`

If the uniform electric field is `3xx10^(3)hatiNC^(-1)`, then the flux of this field through a square of 10 cm on a side whose plane is parallel to the y-z- plane gt?A. `30Nm^(2)C^(-1)`B. `60Nm^(2)C^(-1)`C. `15Nm^(2)C^(-1)`D. `25Nm^(2)C^(-1)`

L shaped rod has equal and opposite charge `(+- Q)` spread along its both arms (see figure). (a) What is direction of electric field at point P? (b) Write electric potential at P.