Capacitors Questions and Answers

The plate separation in a parallel plate condenser is d and plate area is A If it is charged to V volt battery is discon nected then the work done in increasing the plate separation to 2d will be 3 AV d 1 2 2 AV d 2e AV AV 2 d 2d u hottery is disconnected Now the capacitor is connected to 3 4 4

1 300 V 2 600 V 3 100 V A capacitor is charged by connecting a battery across its plates It stores energy U Now the battery is disconnected and another identical capacitor is connected across it then the energy stored by both capacitors of the system will be 1 U U F 3 2U 2 allol plate capacitor the distance between the plates is d and potential difference across plates is V Energy stored

17 Two condensers C and C in a circuit are joined as shown in figure The potential of point A is V and that of B is V2 The potential of point D will be 1 2 3 4 A V V V C C V C V C C 2 C V C V C C C V C V 2 D C B 2

A coil of inductance L 2 0 uH and resistance R 1 Q2 is connected to an ideal source of constant rolini emf 3 V as shown in the figure The amount of E heat in J produced in the coil after the switch S is disconnected is qe is O n doel hi L R 10000 www R 22 S dalar HH 3 V AV er gain to

The plates of a parallel plate capacitor are separated by d cm A plate of thickness t cm with dielectric constant k is inserted and the remaining space is filled with a plate of dielectric constant k If Q is the charge on the capacitor and area of plates is A cm each then potential difference between the plates is 4 Q t B C A k Q Ak Two identical capacitors have A d t k k 4 Q k A t k d t D Q k A t d t k

1 The gap between the plates of a parallel plate capacitor is filled wit isotropic dielectric whose permittivity varies linearly from t in the direction perpendicular to the plates The area of eac plate equals S the separation between the plates is equal to d Find a the capacitance of the capacitor b che b the space density of the bound charges as a function of e if the charge of the capacitor is q and the field E in it is directed toward the growing values

A l F capacitor is connected in the circuit shown below The e m f of the cell is 2 volts and internal resistance is 0 5 ohm The resistors R and R have values 4 ohm and 1 ohm respectively The charge on the capacitor must be 1uF HF 1 2 C 2 1 C 3 1 33 C 7010 E 2V r 0 50 R 192 www R 492 www

13 On closing the switch S the amount of charge flows from A to B is 10 C 10 C A 1 5 C 2 F S 1 F 2 10 C B 5 C 5 C

118 Four metallic plates each with a surface area of one side A are placed at a distance d from each other The plates are connected as shown in the circuit diagram Then the capacitance of the system between a and b is 38 A a b c d 280 A 3d d 2804 d 380 A 2d min s

the capacitors in Fig 4 72 are initially uncharged and are connected as in the diagram with switch S open The applied potential difference is Vah 360 V ab 3 00 F 6 00 F d H a S 6 00 F 3 00 uF Fig 4 72 b

G 4 C 4 is 2 uF The foil is attached to both sides of a paper value of a capacitor formed by thin metallic foil having a thickness of 0 015 mm The dielectric constant of the paper is 2 5 and its breadth is 40 mm The length of the foil used is 1 0 34 m 2 1 33 m N 3 13 4 mm 4 33 9 m

What total energy is stored in the capacitors in the figure below C10 443 uF C 10 7 uF if 1 80 x 104 is stored in the 2 50 uF capaci three significant figures J 2 50 F

A capacitor of capacitance 1uF is discharging through a resistance Initial potential difference across capacitor is 12V At t 1 10 s potential difference across capacitor becomes 6V Find value of resistance R 1 1 443 x 104 3 1 443 x 105 Q 2 2 886 x 105 Q 4 1 443 x 106

Three uncharged capacitors are connected with a battery as show in the figure The work done by the battery in fully charging the capacitors will be 6 F 6 F HH 3 uF 41 O 0 6 J 10 V O 0 3 mJ O 0 3 J O 0 6 MJ mJ

2 8 A capacitor of capacitance of 2 F is charged to a potential difference of 200V after disconnecting from the battery it is connected in parallel with another uncharged capacitor The final common potential is 20V then the capacitance of second capacitor is A 2 F C 18 F B 4 F D 16 F

A capacitor has square plates each of side a making an angle with each other as a a0 Find the shown in fig for small 9 the capacitance C is given by C value of n CATHE SRAM the

C 2 37 In the circuit shown in figure 2 257 the switch S is first closed It is then opened after a long time and then S is closed What is the final charge on C C 3 F A 120 C C 40 C C 6 F B 20V Figure 2 257 B 80 C D 20 C S S

8 In the circuit shown the capacitor initially had a charge 5 C as shown in the figure The switch is closed at time t 0 Find i the initial current through the resistor ii the net heat dissipated after a long time iii the charge across the capacitor plates in time t 10V 1pF 5pc

A parallel plate air core capacitor is connected across a source of constant potential difference When a dielectric plate is introduced between the two plates then A some charge from the capacitor will flow back into the source ce some extra charge from the source will flow into the capacitor C the electric field intensity between the two plates does not change D the electric field intensity between the two plates will decrease

dentical parallel plate capacitors of capacitance Ceach have plates of area A separated by a distance d The space between the plates of the two capacitors is filled with three dielectrics of equal thickness and dielectric constants K K and K The first capacitor is filled as shown in fig 1 and the second one is filled as shown in fig II Assume the plates of the capacitor are at the top and bottom in the two figures If these two modified capacitors are charged by the same potential V the ratio of the energy stored in the two would be E refers to capacitor 1 and E to capacitor II A B 1 11 E K K K K K K K K K K K K E E K K K K K KK K K E 9K K K YOU MARKED X

6 A parallel plate air capacitor consists of two plates each of area 0 01m separated by a distance of 0 1 mm Vit is charged to a potential of 50 volt Calculate a capacitance b charge and c energy stored Ans a 885 4pF b 0 0443 C c 1 11 x 10 J 7 Three capacitors of capacitances 2 F 3uF and 6 F are first connected in series and then in parallel 1 111

The figure shows four identical conducting plates each of area A The separation between the consecutive plates is equal to L When both the switches xV A Find the value of x Treat symbols as having are closed then q L usual meaning 4V 9 O

n the given circuit a charge of 80 C is given to the left plate of 4 F capacitor Then in steady state energy stored inside 2 F capacitor will E 2 F 80 C 4 F O100 J O200 J O 150 J 3 F

A parallel plate capacitor with plates of area 25cm is separated by a distance of 0 05mm The dielectric constant of t he medium between the plates is 8 Th e capacitor is connected to a battery of potential difference 50V Calculate a t he charge collected by the capacitor an d b the electric field between the plate

On increasing the plate separation of a charged capacitor with insulated hand with battery still connected the stored energy O Increases O Decreases Remains constant Becomes zero

View In English In the circuit shown in figure K is open The charge on capacitor C in steady state is q Now key is closed and at steady state the charge on C is 92 The ratio of charges 1 is 1 Correct Answer 1 Your Answer 3 Status incorrect 3 2 2 3 www R 1 7 C 3 E K 2R 1 4 1 2

A parallel plate capacitor having capacitance Co is connected to a battery of emf E It is then disconnected from the battery and a dielectric slab of dielectric constant k completely filling the air gap of the capacitor is inserted in it If AU indicates the change in energy then A AU 0 1 B AU C E K 1 C AU 2 1 C E 1 1 D AU k k

Won t there be potential difference due to 3V battery acr ss the capacitor 14 10V 24 zero 6 92 2 02 wwwwww 1092 3V 3 F HE Find the charge on 3uF capacitor initially it was zero 1 6 C 2 30 C 3 81 C 205

0 A spherical capacitor has an inner sphere of radius 12 cm and an outer sphere of radius 13 cm The outer sphere is earthed and the inner sphere is given a charge of 2 5 C The space between the concentric spheres is filled with a liquid of dielectric constant 32 Determine the potential of the inner sphere 1 400V 2 450 V 3 500V 4 300V

Parallel plate capacitors with a plate sperati on of 1 cm stores 0 02 J of electrostatic en ergy when charged by a battery If it has a c onducting slab between its plates and when charged by a same battery it stores 0 05 Jo f energy Find the thickness of the slab

Two capacitors C C and C 3C are connected as shown in figure Initially key K is open and capacitor C holds charge Q after closing the key K the charge on each capacitor at steady state will be C A C Q Q 4 4 3Q 3Q 4 4 B Q 3Q 44 D 2 0 3 C

When an AC voltage of 220 V is applied to the capacitor C a the current is in phase with the applied voltage b the charge on the plates is in phase with the applied voltage c the maximum voltage between plates is 220 V d power delivered to the capacitor is infinite

8 A parallel plate capacitor is charged to a potential difference V by a DC source and the If the distance between the plates is doubled Capacitance will change t of initial capacitance disconnected a Half b Double c remain same d four times

A parallel plate capacitor with A wL is partially filled to a distance h with a material of dielectric constant K a What is its capacitance as a function of h b The internal capacitance has a charge Q find the potential energy as a function of h What if h 0 or h L c If F U h find the corresponding force

Consider a parallel plate capacitor for which the plates are separated by a vertical distance 2d Suppose that the space between the plates is filled with two slabs of linear dielectrics each of thickness d The upper slab has dielectric constant 3 and the lower slab has dielectric constant 2 If the free charge density on the upper and lower plate is o and respectively calculate for each slab a the electric displacement b the electric field c the polarization d the location and value of the bound charges

A cylindrical capacitor has length 54 cm and radii 4 cm and 3 cm Potential of the inner cylinder when it is given a charge InC and outer cylinder is grounded 1 10 volt 3 105 volt 2 10 volt 4 10 volt

at A and B are same An air capacitor has capacitance 70 F with a separation between plates 20 mm Now distance between plates is doubled and dielectric of k 2 thickness 10 mm is inserted between the plates of capacitor then its capacitance becomes 1 35 F 2 40 F 3 50 F

In the given figure charge on capacitor C C 2 F H C 1 F 1 22 C C 4 F HH HH 66V C 3 F 2 44 C

3 If dielectric constant and dielectric strength be denoted by k x respectively then a material suitable for use as a dielectric in a capacitor must have 1 high k high x 3 low k high x 2 high k low x 4 low k low x

the given circuit below calculate the ratio of charges on 6F capacitor in steady state in the circuit for the cases when switch S is open and switch S is closed 3uF 6uF 1 F www 1011 100v 021 www 1002 12

The capacitor C shown in the figure carries zero charges initially At t 0 switch K is closed Then choose the incorrect option www HE O O K at t 0 R produces maximum heat per sec for 0 t dW du dH dt dt dt the electrostatic flux 4 between the plates of the capacitor remains same during the charging of capacitor for 0 t a magnetic compass will show deflection near the capacitor

3 low k A parallel plate capacitor has a uniform elect field E V m in the space between the pla If the distance between the plates is d m area of each plate is A m the energy Jc stored in the capacitor is 1 E 1 1250 1 U E Ad 2 EAd E 4 E Ad E

A parallel plate capacitor is connected with a resistance R and a cell of emf e as shown in figure The capacitor is fully charged Keeping the right plate fixed the left plate is moved slowly towards further left with a variable velocity such that the current flowing through the circuit is constant Then the variation of with separation a between the plates is represented by curve Answer A www Your Attempt K 12 Correct answer Rate this question

5 Two identical condensers are first connected in series and then in parallel If the equivalent capacity in parallel grouping is 40 F equivalent capacity in series group ing is 1 1 F 4 15 F 2154 F 3 10 F

Consider a circuit of high capacitance and very hight resistance R a battery of emf E and switch S The switch is closed at t 0 At t the heat loss through the circuit will be CE A www 20 B there will be negligible heat loss as the current in the circuit will be negligible at all instant hence i R is also negligible the heat loss in the circuit always depend upon rate of charging of capacitor A the heat loss in the circuit does not depend upon rate of charging of the capaci E

Four metallic plates each with a surface area A are placed at a distance d from each other as shown in the figure If points A and B are connected with a battery of emf V then the charge on the plate a will be O 3 A V d b C d Read More B

In the following figure C 5 F C C 10 F and 20 V Initially the switch S is connected to point A until capacitor C is fully charged Afterwards switch is thrown to left side and connected to point B The charge on capacitor C after equilibrium is reached will be Options 1 40 C B HE A 8 20v

point Two capacitors C 4 F and C 7 F are connected across a 40 V battery The battery is removed and plates of opposite sign are connected Find the final charge and potential ference for each capacitor 1 C

Five capacitors of 10 F capacity each are connected to a DC potential of 100 volts as shown in figure The equivalent capacitance between the points A and B will be equal to 10 F 10 F 10 F 140 F 10 F 100V B 10 F Question Type Single Correct Type

In the circuit shown the switch S is closed at t 0 The capacitor is initially uncharged Then the current through the resistor R 802 at t 0 4 x 103 sec is Take e 0 135 A 0 18 A B 0 27 A C 0 54 A D 0 72 A R 80 www S 40 201 HH m