1638 + Interview Questions in ELECTROSTATICS IN GENERAL AWARENESS Page 25 InterviewSolution

1201.	A parallel plate capacitor is to be designed with a voltage rating 1 KV using a material of dielectrical constant 3 and dielectric strength about `10^(7) Vm^(-1)`. [Dielectric strength is the maximum electric field a material can tolerate without break down, i.e, without starting to conduct electrically through partial ionisation. For safety, we should like the field never to exceed say `10%` of the dielectric strength]. What minimum area of the plates is required to have a capacitance of 50 pF ?
Answer» Here, `V = 1 kV = 1000 volt , K = in_(r) = 3` , Dielectric strength `= 10^(7) V//m` As electric field at the most should be `10%` of dielectric strength, due to reasons of safety, `:. E = 10% of 10^(7) V//m, A = ?, C = 50 pF = 50xx10^(-12) F` Now, `C = (in_(0) in_(r) A)/(d) A = (Cd)/(in_(0) in_(r)) = (50xx10^(-12)xx10^(-3))/(8.85xx10^(-12)xx3) = 1.9xx10^(-3) m^(2)`

Discussion

1202.	There is a semi-infinite hollow cylindrical pipe (i.e. one end extends to infinity) with uniform surface charge density. What is the direction of electric field at a point A on the circular end face?
Answer» Correct Answer - Parallel to the axis of the cylinder.

Discussion

1203.	A spherical conductor `A` lies inside a hollow spherical conductor `B`. Charges `Q_(1)` and `Q_(2)` are given to `A` and `B` respectively (Choose the incorrect option)A. Charge `Q_(1)` will appear on the outer surface of `A`B. Charge `-Q_(1)` will appear on the inner surface of `B`C. Charge `Q_(2)` will appear on the outer surface of `B`D. Charge `Q_(1) + Q_(2)` will appear on the outer surface of `B`
Answer» Correct Answer - 3

Discussion

1204.	In the above question, if battery is removed after charging the condenser & dielectric slab inteoduced, how are all the fice parameters affected ?
Answer» When battery is removed, charge Q remains constant, capacity `C = KC_(0)` increases. Potential diff. `V = Q//C` decreases. Electric field `E = (V )/(d)` decreases. Energy stored `= (1)/(2) (Q^(2))/(C )` decreases.

Discussion

1205.	Two condenser one of capacity C and other of capacity C/2 are connected to 9 V battery, as shown in figure. The work done in the charging fully both condensers is A. `1//4CV^(2)`B. `2CV^(2)`C. `3//4CV^(2)`D. `1//2CV^(2)`
Answer» Correct Answer - C Two two condensers are connected in parallel, we have `C_(p)=C+(C)/(2)=(3C)/(2)` `therefore` Total work done in charging both the condensers `W=(1)/(2)C_(p)V^(2)=(1)/(2)xx(3C)/(2)V^(2)=(3)/(4)CV^(2)`

Discussion

1206.	Let there be a spherically symmetric charge distribution with charge density varying as `rho(r)=rho(5/4-r/R)` upto `r=R`, and `rho(r)=0` for `rgtR`, where r is the distance from the origin. The electric field at a distance r(rltR) from the origin is given byA. ` (4 pi rho_0r)/(3varepsilon_0) (5/3 -r/R)`B. ` (4 pi rho_0r)/(3varepsilon_0) (5/3 -r/R)`C. ` (4 pi rho_0r)/(3varepsilon_0) (5/4 -r/R)`D. ` (4 pi rho_0r)/(3varepsilon_0) (5/4 -r/R)`
Answer» Correct Answer - B Consider a sherical shell of radius `x` and thickness dx. Charge on it dq `dq = prop xx 4 pi x^2 . Dx` ` dq = prop_0 (5/4 - x/R) xx 4 pi x^2 dx` `q = 4 pi prop _0 int_0^r ((5 x^2)/4 - x^3/R) dx` `q = 4 prop_0 ( (5r^3)/( 3 xx 4) - r^2/(4R))` `E = (kq)/r^2 = 1/( 4 pir^2) xx 4 pi prop_0 ((5r^3)/( 3xx4) - r^4/(4R))` ` E = ( prop_0r)/(4 prop_0) (5 /3 - r/R)`.

Discussion

1207.	Electric potential is a scalar quantity. Due to a point charge charge q at distance r, the potential is given by `V=(q)/(4pi in_(0)r)`. A point charge q is placed at `(3a, 0)` and another charge `-2q` is placed at `(-3a, 0)`. At how many points on the x-axis, (at finite distance) electric potential will be zero?A. 1B. 2C. 3D. 4
Answer» Correct Answer - B

Discussion

1208.	Electric potential is a scalar quantity. Due to a point charge charge q at distance r, the potential is given by `V=(q)/(4pi in_(0)r)`. A point charge q is placed at `(3a, 0)` and another charge `-2q` is placed at `(-3a, 0)`. If we plot a graph of potential (V) on x-axis it will be like:A. B. C. D.
Answer» Correct Answer - D

Discussion

1209.	A network of four each of `12 mu F` capacitance is connected to a `500 V` apply as shown in Fig. (a) Equivalent capacitance of the network. (b) Charge on each capacitor.
Answer» Correct Answer - (a) `16 muF` (b) `q_(1) = q_(2) = q_(3) = 2000 muC, q_(4) = 6000 muC` Here, `C_(1), C_(2), C_(3)` are in series. `C_(123) = (12 muF)/(3) = 4 muF` As `C_(4)` is in parallel with this combination, `:. C_(eq) = 4+12 = 16 muF` `q_(1) = q_(2) = q_(3) = C_(123) V = 4 muF xx 500 = 2000 muC` `q_(4) = C_(4) V = 12 muF xx 500 V = 6000 muC`

Discussion

1210.	A capacitor is conneted to a cell emf `E` having some internal resistance `r`. The potential difference across theA. cell is `varepsilon`B. cell is `lt varepsilon`C. capacitor is `lt varepsilon`D. capacitor is `gt varepsilon`
Answer» Correct Answer - A

Discussion

1211.	The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 8B. 4C. 6D. 2
Answer» Correct Answer - D `C_("air")=C,C_(m)=4/3C_("air")=4/3C` `C_(m)=(Ain_(0))/(d-t(1-1/k))` `=(Ain_(0))/(d-d/2(1-1/k))=(Ain_(0))/(d(1-1/2+1/k))` `C_(m)=(Ain_(0))/(d(1/2+1/k))" "(therefore(Ain_(0))/d=C)` `(4C)/3=C/(1/2+1/k)" "thereforek=2`

Discussion

1212.	The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 2B. 4C. 6D. 8
Answer» Correct Answer - A

Discussion

1213.	The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 6B. 8C. 2D. 4
Answer» Correct Answer - C Original capacity, `C_(0)=(epsilon_(0)A)/(d)` On introducing dielectric slab of thickness d/2, the capacity becomes `C=(epsilon_(0)A)/((d-(d)/(2))+2(d)/(2K))=(epsilon_(0)A)/((d)/(2)(1+(1)/(k)))` `"As "C=(4)/(3)C_(0)` `therefore" "(epsilon_(0)A)/((d)/(2)(1+(1)/(k)))=(4)/(3)(epsilon_(0)A)/(d)rArr 1+(1)/(k)=(3)/(2) rArrK=2`

Discussion

1214.	In a parallel plate capacitor of capacitance `C`, a metal sheet is inserted between the plates, parallel to them. If the thickness of the sheet is half of the separation between the plates. The capacitance will beA. `4C`B. `2C`C. `C//2`D. `C//4`
Answer» Correct Answer - B

Discussion

1215.	In the circuit shown, a potential difference of `60V` is applied acrodd.`AB`. The potential difference between the point `M` and `N` is- A. `10V`B. `15V`C. `20V`D. `30V`
Answer» Correct Answer - D

Discussion

1216.	Five capacitors, each of capacitance value `C` are connecteed as shown in the figure. The ratio of capacitance between `P` and `R`, and the capacitance between `P` and `Q`, is. A. `3 : 1`B. `5 : 2`C. `2 : 3`D. `1 : 1`
Answer» Correct Answer - C In fig four capacitors are in series `therefore" "C_(S)=C/4` Now `C_(s)` and C are in parallel `therefore" "C_(PQ)=C_(P)=C_(S)+C` `=C/4+C=(5C)/4` Now `C_(PR)=C/2+C/3=(5C)/6` `C_(PR)/C_(PQ)=((5C)/6)/((5C)/4)=2/3`

Discussion

1217.	Two capacitors of capacitances `3 muF` and `6 muF` are charged to a potential of `12 V` each. They are now connected to each other, with the positive plate of each joined to the negative plate of the other. The potential difference across each will beA. zeroB. `3V`C. `4V`D. `6V`
Answer» Correct Answer - C

Discussion

1218.	Three capacitors of capacitances `2 muF`, `3mu F` and `6muF` are connected in series with a 12 V battery. All the connecting wire are disconnected, the three positive plates are connected together and the three negative plates are connected together. Find the charges on the three capacitors after the reconnection.
Answer» Correct Answer - ` (72)/(11) mu C ; (108)/(11) mu C ; (216)/(11) muC` `(1)/(C_(s)) = (1)/(C_(1)) + (1)/(C_(2)) + (1)/(C_(3)) = (1)/(2) + (1)/(3) + (1)/(6) = (6)/(6)` Charge on each capacitor `= C_(s) xx V` `= 1xx12 = 12 mu C` Thus charges of `+- 12 mu C` appear on the plates of each of the three capacitors. When connected in parallel, thier potentail becomes equal as the charges redistribute themselves, Common potentail, `V = ("total charge")/("total capacity") = (12xx3)/(2+3-6) = (36)/(11)` `:. Q_(1) = C_(1) V = 2xx (36)/(11) = (72)/(11) mu C` `Q_(2) = C_(2) V = 3 xx (36)/(11) = (108)/(11) mu C` `Q_(3) = C_(3) V = 6 xx (36)/(11) = (216)/(11) muC`

Discussion

1219.	Five capacitors of capacitances `C_(1) = C_(5) = 1 muF , C_(2) = C_(3) = C_(4) = 2 muF` are connectes as shown in Fig. Calculate equivalent capacitance of the system between points `A` and `B`.
Answer» Correct Answer - `2 muF` In Fig, are in series. This combination capacity of `C_(2), C_(3), C_(1)` is in series with `C_(4)`. The combination is in parallel with `C_(5)`.

Discussion

1220.	Find the equivalent capacitane between the points `P` and `Q` as shown in Fig. Given `C = 18 muF` and `C_(1) = 12 muF`
Answer» Correct Answer - `11 muF` Equivalent capacitance between points `F` and `B` is `= (18xx18)/(18+18) + 18 = 27 muF` Equiavlent capacitance between `A` and `B` `= 12 + (18xx27)/(18+27) = 22.8 = 23 muF` Equivalent capacitance between `A` and `E` `= (23xx18)/(23+18) + 18 = 28 muF` Equivalent capacitance between `D` and `E` `= (28xx18)/(28+18) + 12 = 23muF` Equivalent capacitance between `D` and `Q` `= (23xx18)/(23+18) + 18 = 28 muF` Equivalent capacitance between `P` and `Q` `= (28xx18)/(28+18) = 11 muF`

Discussion

1221.	Two capacitors have a capacitance of `5 muF` when connected in parallel and `1.2 muF` when connected in series. Calculate their capacitance.
Answer» Correct Answer - `2 muF , 3 muF` Let two capacitances be `C_(1)` and `C_(2)` `C_(1) + C_(2) = 5 muF` and `(C_(1) C_(2))/(C_(1) + C_(2)) = 1.2 muF` On solving, we get `C_(1) = 2 muF, C_(2) = 3 muF`

Discussion

1222.	Connect three capacitors of `3 muF, 3 muF` and `6 muF` such that their equivalent capacitance is `5 muF`.
Answer» Correct Answer - Series combination of `3 muF` and `6 muF` in parallel with `3 muF` We will connect series combinition of `3 mu r` and `6 muF` in parallel with the third capacitance of `3 muF` `(1)/(C_(S)) = (1)/(3) + (1)/(6)` OR `C_(S) = 2 muf` `C_(P) = 2 muF + 3 muF = 5 muF`

Discussion

1223.	An infinite number of identical capacitors each of capacitance `1 muF` are connected `1 muF` are connected as shown in Fig. Then the equivalent capacitance between `A` and `B` is A. `1 muF`B. `2 muF`C. `(1)/(2) muF`D. `oo`
Answer» Correct Answer - B In each row, Fig, the capacitance are in series, and different rows of capacitance are joined in parallel. Therefore, total capacity `C = C + (C )/(2) + (C )/(4) + (C )/(8) + (C )/(16) + …… oo` `= C [1 + (1 )/(2) + (1)/(4) + (1)/(8) + (1)/(16) + …… oo]` `= C [(1)/(1-1//2)] = 2C = 2 muF`

Discussion

1224.	An infinite number of identical capacitors each of capacitance `1 muF` are connected `1 muF` are connected as shown in Fig. Then the equivalent capacitance between `A` and `B` is A. `1muF`B. `2muF`C. `0.5muF`D. `infty`
Answer» Correct Answer - B `C_(AB)=C_(P)=1+1/2+1/4+1/8+1/16+............` = 1 + 1 `=2muF`

Discussion

1225.	The graph in Fig, shows variation of total energy U stored in the capacitor against the value of the capacitance C itself. Which of the two - the charge on capacitor or potential used to charge is kept constant for this graph ?
Answer» It is known that energy stored in capacitor, `U = (Q^(2))/(2C) = (1)/(2) CV^(2)` If V were constant, `U prop C`. The graph between U and C should be a straight line, which is not. If Q is constant, `U prop (1)/(C )` , which is the kind of graph given.

Discussion

1226.	Net capacitance of three identical capacitors in series is `1 muF`. What will be their net capacitance in parallel ? Find the ratio of energy stored in two configurations if they are connected to the same source.
Answer» Correct Answer - `9 muF ; 1 : 9` Let `C` be the capacity each condenser, ` (1)/(C_(s)) = (1)/(C ) + (1)/(C ) +(1)/(C ) = (3)/(C ) = 1 muF :. C = 3 muF` `C_(p) = C_(1) + C_(2) + C_(3) = 3 C = 3xx3 = 9 muF` Let `V` be the `p.d` of same source. `u_(s) = (1)/(2) C_(s) V^(2)` and `u_(p) = (1)/(2) C_(p) V^(2)` `:. (u_(s))/(u_(p)) = (C_(s))/(C_(p)) = (C//3)/(3C) = (1)/(9)`

Discussion

1227.	In what form is the energy stored in a charged capacitance ?
Answer» Energy is stored in the form of electrostatic potential energy in the electric field between the plates of capacitor.

Discussion

1228.	Name the physical quantity whose S.I. unit is J C–1 .Is it a scalar or a vector quantity?
Answer» J C^–1 is the S.I. unit of electrostatic potential. It is a scalar quantity.

Discussion

1229.	The Capacitance of a conductor is 1 Farad. What do you mean by this statement ?
Answer» A conductor is said to have capacitance of 1 farad, if I coulomb of charge increases its electric potential through 1 volt.

Discussion

1230.	Write two applications fo capacitors in electrical circuits ?
Answer» (i) Capacitors are used in ratio circuits for tunning purposes. (ii) Capacitors are used in power supplies for smoothening the rectified current.

Discussion

1231.	Write the physical quantity that has its unit coulomb `vol t^(-1)`. Is it a vector or a scalar quantity ?
Answer» Capacitance has its unit coulomb `vol t^(-1)`. It is a scalar quanity.

Discussion

1232.	An electric charge `10^-3muC` is placed at the origin (0, 0) of X-Y co-ordinate system. Two points A and B are situated at `(sqrt2, sqrt2)` and (2, 0) respectively. The potential difference between the points A and B will beA. ` 4.5 volt `B. `9 volt`C. `zero`D. `2 volt
Answer» Correct Answer - C Since, `V_A = 9 xx 10^9 (10^(-9))/({2 +2}^(1//2) = 4.5` volt, `V_B = 9 xx 10^9 (10^(-9))/{4 + 0 }^(1//2)` volt , `V_A - V_B =0` .

Discussion

1233.	The potential at a point x ( measured in `mu` m) due to some charges situated on the x-axis is given by `V(x)=20//(x^2-4) vol t`A. ` (10//9)` volt //mumand in the + ve `x` directionB. `( 5 //3)` volt //mu m and in the - ve `x` directionC. `( 5 //3 ) volt //` mum and in the `+ ve 9 x` directionD. `(10 //9 ) volt //`volt //mum in the - ve `x` direction
Answer» Correct Answer - A ` v (x) = (20)/(x^2 -4), E = - (dv)/(dx) =- d/(dx) ((20)/(x^2 -4)) = (20)/((x^2 - 4)^@) (2 x)` `E at x = 4 mu m, ((20)(2 xx 4))/(144) = (10)/9` volt// mu m Also as `x` increases , `V` decreases So , `E` is along `+ ve x -` axis .

Discussion

1234.	A thin spherical shell of radius R has charge Q spread uniformly over its surface. Which of the following graphs most closely represents the electric field E(r) produced by the shell in the range `0lerltoo`, where r is the distance from the centre of the shell?A. B. C. D.
Answer» Correct Answer - B Since, the electric field inside the shell is zero and outside , the electric field is given as `(kQ)/(r^2)` ., where ` r=` distance from centre . So. Graph is as shown in option (4).

Discussion

1235.	Electric intensity at a point due to a charged cylinder of infinite length is inversely proportional to itsA. distanceB. square of distanceC. cube of distanceD. none of these
Answer» Correct Answer - A

Discussion

1236.	The intensity of electric field at a point clone but outside a charged conducting cylinder is proportional to [r is the distance of the point from the axis of the cylinder](A) \(\cfrac1{r}\)(B) \(\cfrac1{r^2}\)(C) \(\cfrac1{r^3}\)(D) r.
Answer» Correct option is (A) \(\cfrac1{r}\)

Discussion

1237.	The electric flux over a sphere of radius 1.0 m is ø. If the radius of the sphere is doubled without changing the charge, the flux will be(A) 4ø (B) 2ø (C) ø (D) 8ø
Answer» Correct option is: (C) ø

Discussion

1238.	If the radius of a sphere is doubled without chianging the charge on it then the electric flux originating from the sphere is (A) double (B) half (C) the same (D) zero.
Answer» (C) the same

Discussion

1239.	The number of tubes of force originating from a charge of magnitude q areA. `q/(in_(0)k)`B. `q/(in_(0))`C. `qin_(0)k`D. `(in_(0)k)/q`
Answer» Correct Answer - A

Discussion

1240.	The number of tubes of induction originating from a unit positive charge isA. 1B. `q//in_(0)`C. `qin_(0)`D. `in_(0)`
Answer» Correct Answer - A

Discussion

1241.	The number of tubes of force originating from a point charge of `17.7xx10^(-8)C` placed in dielectric medium of dielectric constant 4 areA. `3000Nm^(2)//C`B. `5000Nm^(2)//C`C. `6000Nm^(2)//C`D. `5500Nm^(2)//C`
Answer» Correct Answer - B `N=q/(epsi_(0)k)=(17.7xx10^(-8))/(8.85xx10^(-12)xx4)=5000Nm^(2)//C.`

Discussion

1242.	A charge of `17*7xx10^(-4)C` is distributed over a large sheet of area `400 m^(2)`. Calculate the electric field intensity at a distance of `10 cm` from it.
Answer» Here `q = 177xx10^(-4) C, A = 400 m^(2), E = ?, r = 10 cm , 10^(-1) m` In case of a large plane sheet, distance of the point `(=r)` does not manner. `E = (sigma)/(2 in_(0)) = (q//A)/(2in_(0)) = (q)/(2in_(0) A) = (177xx10^(-4))/(2xx(885xx10^(-12))xx400) = 25xx10^(5) N//C`

Discussion

1243.	A `12 pF` capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor ? If another capacitor of `6 pF` is connected across the combination, find the charge stored and potential difference across each capacitor.
Answer» Here, `C_(1) = 12 pF = 12xx10^(-12) F`. V = 50 volt. Electrostaic energy stored `U = (1)/(2) C_(1) V^(2)` `= (1)/(2)xx12xx10^(-12) (50)^(2)` `U = 1.5xx10^(-8) J` Now, `C_(2) = 6 pF = 6xx10^(-12) F` `(1)/(C_(s)) = (1)/(C_(1)) + (1)/(C_(2)) = (1)/(12) + (1)/(6) = (3)/(12) = (1)/(4)` `C_(s) = 4 pF = 4xx10^(-12) F` Charge on each condenser, `q_(1) = q_(2) = C_(s) V = 4xx10^(-12) xx50` `= 2xx10^(-10) C` `V_(1) = (q_(1))/(C_(1)) = (2xx10^(-10))/(12xx10^(-12)) = (50)/(3)` volt `V_(2) = (q_(2))/(C_(2)) = (2xx10^(-10))/(6xx10^(-12)) = (100)/(3)` volt

Discussion

1244.	A 700 pF capacitor is charged by a 50 V battery. The electrostatic energy stored it isA. `6.7xx10^(-7)J`B. `8.7xx10^(-7)J`C. `9.7xx10^(7)J`D. `6.7xx10^(7)J`
Answer» Correct Answer - B C = 700pF, V = 50V, E = ? `E=1/2CV^(2)=(700xx10^(-12)xx25xx10^(2))/2` `=8.7xx10^(-7)J`

Discussion

1245.	A point charge `Q` is located on the axis of disc of a radius `R` at a distance `a` from the plane of the disc . If one fourth `(1//4th)` of the flux from the charge passes through the disc, then find the relation between `a` & `R `. .
Answer» Correct Answer - [`a = (R)/(sqrt3)`]

Discussion

1246.	A very long uniformly charged thread oriented along the axis of a a circle of radius `R` rests on its centre with one of the ends. The charge of the thread per unit length is equal to `lambda`. Find the flux of the vector `E` across the circle area.
Answer» Correct Answer - `[\|phi\| = (1)/(2)lambdaR//epsi_(0)`. The sign of `Phi` depends on how the direction of the normal to the circle is chosen. ]

Discussion

1247.	Figure shows sone equipotential surfaces produce by some charges. At which point, the value of electric field is greatest ?
Answer» E is larger where equipotential surface are closer. ELOF are `bot` to equipotential surfaces. In the figure, we can see that for point B, they are closer so E at point B is maximum

Discussion

1248.	The cell membrane of a resting nerve in a human body has a thickness of 75 Å. If potential difference between the two sides of membrace is 0.06 V. Then intensity of electric field isA. `8xx10^(6)V//m`B. `4xx10^(6)V//m`C. `8xx10^(-6)V//m`D. `4xx10^(-6)V//m`
Answer» Correct Answer - A `E=V/d=0.06/(75xx10^(-10))=8xx10^(6)V//m.`

Discussion

1249.	A point charge q produces an electric field of magnitude 2 N C-1 at a point distant 0.25 m from it. What is the value of charge?(A) 1.39 × 10-11 C(B) 1.39 × 1011 C(C) 13.9 × 10-11 C(D) 13.9 × 1011 C
Answer» Correct option is: (A) 1.39 × 10^-11C

Discussion

1250.	The charge on the electron is 1.6 × 10-19 C. The number of electrons need to be removed from a metal sphere of 0.05 m radius so as to acquire a charge of 4 × 10-15 C is(A) 1.25 × 104(B) 1.25 × 103(C) 2.5 × 103(D) 2.5 × 104
Answer» Correct option is: (D) 2.5 × 10⁴

Discussion

Explore topic-wise InterviewSolutions in .

There is a semi-infinite hollow cylindrical pipe (i.e. one end extends to infinity) with uniform surface charge density. What is the direction of electric field at a point A on the circular end face?

In the above question, if battery is removed after charging the condenser & dielectric slab inteoduced, how are all the fice parameters affected ?

Two condenser one of capacity C and other of capacity C/2 are connected to 9 V battery, as shown in figure. The work done in the charging fully both condensers is A. `1//4CV^(2)`B. `2CV^(2)`C. `3//4CV^(2)`D. `1//2CV^(2)`

Electric potential is a scalar quantity. Due to a point charge charge q at distance r, the potential is given by `V=(q)/(4pi in_(0)r)`. A point charge q is placed at `(3a, 0)` and another charge `-2q` is placed at `(-3a, 0)`. If we plot a graph of potential (V) on x-axis it will be like:A. B. C. D.

A network of four each of `12 mu F` capacitance is connected to a `500 V` apply as shown in Fig. (a) Equivalent capacitance of the network. (b) Charge on each capacitor.

A capacitor is conneted to a cell emf `E` having some internal resistance `r`. The potential difference across theA. cell is `varepsilon`B. cell is `lt varepsilon`C. capacitor is `lt varepsilon`D. capacitor is `gt varepsilon`

The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 8B. 4C. 6D. 2

The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 2B. 4C. 6D. 8

The capacitance of a capacitor between` 4//3` times its original value if a dielectric slab of thickness `t=d//2` is inserted between the plates (d is the separation between the plates). What is the dielectric consant of the slab?A. 6B. 8C. 2D. 4

In a parallel plate capacitor of capacitance `C`, a metal sheet is inserted between the plates, parallel to them. If the thickness of the sheet is half of the separation between the plates. The capacitance will beA. `4C`B. `2C`C. `C//2`D. `C//4`

In the circuit shown, a potential difference of `60V` is applied acrodd.`AB`. The potential difference between the point `M` and `N` is- A. `10V`B. `15V`C. `20V`D. `30V`

Five capacitors, each of capacitance value `C` are connecteed as shown in the figure. The ratio of capacitance between `P` and `R`, and the capacitance between `P` and `Q`, is. A. `3 : 1`B. `5 : 2`C. `2 : 3`D. `1 : 1`

Two capacitors of capacitances `3 muF` and `6 muF` are charged to a potential of `12 V` each. They are now connected to each other, with the positive plate of each joined to the negative plate of the other. The potential difference across each will beA. zeroB. `3V`C. `4V`D. `6V`

Five capacitors of capacitances `C_(1) = C_(5) = 1 muF , C_(2) = C_(3) = C_(4) = 2 muF` are connectes as shown in Fig. Calculate equivalent capacitance of the system between points `A` and `B`.

Find the equivalent capacitane between the points `P` and `Q` as shown in Fig. Given `C = 18 muF` and `C_(1) = 12 muF`

Two capacitors have a capacitance of `5 muF` when connected in parallel and `1.2 muF` when connected in series. Calculate their capacitance.

Connect three capacitors of `3 muF, 3 muF` and `6 muF` such that their equivalent capacitance is `5 muF`.

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

An infinite number of identical capacitors each of capacitance `1 muF` are connected `1 muF` are connected as shown in Fig. Then the equivalent capacitance between `A` and `B` is A. `1muF`B. `2muF`C. `0.5muF`D. `infty`

The graph in Fig, shows variation of total energy U stored in the capacitor against the value of the capacitance C itself. Which of the two - the charge on capacitor or potential used to charge is kept constant for this graph ?

Net capacitance of three identical capacitors in series is `1 muF`. What will be their net capacitance in parallel ? Find the ratio of energy stored in two configurations if they are connected to the same source.

In what form is the energy stored in a charged capacitance ?

Name the physical quantity whose S.I. unit is J C–1 .Is it a scalar or a vector quantity?

The Capacitance of a conductor is 1 Farad. What do you mean by this statement ?

Write two applications fo capacitors in electrical circuits ?

Write the physical quantity that has its unit coulomb `vol t^(-1)`. Is it a vector or a scalar quantity ?

An electric charge `10^-3muC` is placed at the origin (0, 0) of X-Y co-ordinate system. Two points A and B are situated at `(sqrt2, sqrt2)` and (2, 0) respectively. The potential difference between the points A and B will beA. ` 4.5 volt `B. `9 volt`C. `zero`D. `2 volt

A thin spherical shell of radius R has charge Q spread uniformly over its surface. Which of the following graphs most closely represents the electric field E(r) produced by the shell in the range `0lerltoo`, where r is the distance from the centre of the shell?A. B. C. D.

Electric intensity at a point due to a charged cylinder of infinite length is inversely proportional to itsA. distanceB. square of distanceC. cube of distanceD. none of these

The intensity of electric field at a point clone but outside a charged conducting cylinder is proportional to [r is the distance of the point from the axis of the cylinder](A) \(\cfrac1{r}\)(B) \(\cfrac1{r^2}\)(C) \(\cfrac1{r^3}\)(D) r.

The electric flux over a sphere of radius 1.0 m is ø. If the radius of the sphere is doubled without changing the charge, the flux will be(A) 4ø (B) 2ø (C) ø (D) 8ø

If the radius of a sphere is doubled without chianging the charge on it then the electric flux originating from the sphere is (A) double (B) half (C) the same (D) zero.

The number of tubes of force originating from a charge of magnitude q areA. `q/(in_(0)k)`B. `q/(in_(0))`C. `qin_(0)k`D. `(in_(0)k)/q`

The number of tubes of induction originating from a unit positive charge isA. 1B. `q//in_(0)`C. `qin_(0)`D. `in_(0)`

The number of tubes of force originating from a point charge of `17.7xx10^(-8)C` placed in dielectric medium of dielectric constant 4 areA. `3000Nm^(2)//C`B. `5000Nm^(2)//C`C. `6000Nm^(2)//C`D. `5500Nm^(2)//C`

A charge of `17*7xx10^(-4)C` is distributed over a large sheet of area `400 m^(2)`. Calculate the electric field intensity at a distance of `10 cm` from it.

A `12 pF` capacitor is connected to a 50 V battery. How much electrostatic energy is stored in the capacitor ? If another capacitor of `6 pF` is connected across the combination, find the charge stored and potential difference across each capacitor.

A 700 pF capacitor is charged by a 50 V battery. The electrostatic energy stored it isA. `6.7xx10^(-7)J`B. `8.7xx10^(-7)J`C. `9.7xx10^(7)J`D. `6.7xx10^(7)J`

A point charge `Q` is located on the axis of disc of a radius `R` at a distance `a` from the plane of the disc . If one fourth `(1//4th)` of the flux from the charge passes through the disc, then find the relation between `a` & `R `. .

A very long uniformly charged thread oriented along the axis of a a circle of radius `R` rests on its centre with one of the ends. The charge of the thread per unit length is equal to `lambda`. Find the flux of the vector `E` across the circle area.

Figure shows sone equipotential surfaces produce by some charges. At which point, the value of electric field is greatest ?

The cell membrane of a resting nerve in a human body has a thickness of 75 Å. If potential difference between the two sides of membrace is 0.06 V. Then intensity of electric field isA. `8xx10^(6)V//m`B. `4xx10^(6)V//m`C. `8xx10^(-6)V//m`D. `4xx10^(-6)V//m`

A point charge q produces an electric field of magnitude 2 N C-1 at a point distant 0.25 m from it. What is the value of charge?(A) 1.39 × 10-11 C(B) 1.39 × 1011 C(C) 13.9 × 10-11 C(D) 13.9 × 1011 C

The charge on the electron is 1.6 × 10-19 C. The number of electrons need to be removed from a metal sphere of 0.05 m radius so as to acquire a charge of 4 × 10-15 C is(A) 1.25 × 104(B) 1.25 × 103(C) 2.5 × 103(D) 2.5 × 104