Capacitors Questions and Answers

i In the given figure if each capacitor ha capacitance c then the equivalent capacitance between P and Q of the entire circuit is 1 3 2c 7 5c 2 What in th P 2 4 Q 2 2 25 7c

2 23 A parallel plate capacitor of plate area A and plate separation d is connected across a battery of voltage Vand after charging of capacitor battery is disconnected Now a dielectric slab of relative permittivity k is inserted between the plates to fill the complete space between the plates Find the work done by the external agent in the process of inserting the slab into capacitor AV 1 Ans

The 10 F capacitor was initially charged by a battery After the switches are closed the potential difference across the 10 F capacitor is found to be 15V Find the emf of the battery A 37 5 V B 24 V C 22 5 V D 21 V 20 F 5 F

Two long metallic coaxial cylindrical capacitors of radii R and 2R are carrying charges Q and Q respectively T energy of the capacitor is U For what values of the radii the energy of the capacitor will be 2U

Zero Marks 0 In all other cases Three identical air capacitors having plate separation 3 mm each are connected as shown They are charged by applying a potential difference V and then the source voltage is removed When a 3 mm thick slab is introduced between a the plates the distance between the plates is increased by 2 4 mm to maintain same potential difference Find dielectric constant of the slab

S 6R ww V b 9R www VV a 3R 9R V t 7RC Current through the cell at time t is Options ww 3 e 1 7RC V c 27 3 e 1 3RC V 2 1 3RC S is closed at t 0 3R

3 34 A potential difference of 220V is maintained across a 12000 rheostat as shown in figure 3 390 The voltmeter has a resistance of 6000 and point C is at one fourth of the distance from a to b What is the reading of voltmeter 220V b a Figure 3 390 1

The figure shows a RC circuit with a parallel plate capacitor Before switching on the circuit plate A of the capacitor was given a charge Q while plate B had no net charge Now at t 0 the circuit is switched on Time in seconds will elapse before the net charge on plate A becomes zero is K Value of 125K is Take C 1 F Q 1mC 1000 V and R 250 2x 108 In 3 Q R www A B L

A capacitor with charge Q on it is connected to an inductor L as shown in diagram at t 0 When the switch is flipped from position 1 to 2 the current in the circuit is observed to be at half of its maximum value Then 1 L 2 ellelle A Charge on capacitor at the time was Q 2 Q 3 2 Charge on capacitor at that time was C Total energy lost is Total energy lost is 4C 8C

el in en iii A cylindrical layer of dielectric with dielectric constant k is inserted into a cylindrical capacitor to fill up all the space between the electrodes The mean radius of the electrodes is equal to R the gap between them is equal to d with d R A constant voltage Vis applied across the electrodes of the capacitor Find the magnitude of the electric force pulling the dielectric into the capacitor TRV F k 1 d

y Chemical Kinetics production in Flowering plants Human Reproduction YSICS JEE Founda The equivalent capacitance between points A and B Services Limited as of five identical capacitors of capacitance 2 F as shown in the figure will be A 2 F HH 1 4 F 3 1 F 2 F 2 F 2 F 2 F B 2 2 F 4 10 F

educe circuit below to its Thevenin equivalent circuit which will contain one resistor on apacitor and one power supply Also calculate the current through the circuit after the apacitor s are charged R1 R2 Vdc 14 0 R1 5 0k R2 12 5kQ R3 2 0k2 R4 12 02 R5 5 0k02 R6 1 0k R7 1 2kQ2 R8 4 3k R9 700 R7 R8 C1 20 F C2 15 F C3 5 F R3 R6 w R9 R4 www www R5

The potential energy of each 2uF capacitor is 1 J and that of the 6 F capacitor is 2 J Find i the potential difference between A B ii the potential energy of the upper capacitor

2 A parallel plate capacitor after charging is kept connected to a battery and the plates are pulled apart with the help of insulating handles Now which of the following qunatity will remain constant f 1 Charge 1 2 Capacitance 2 f 3 Energy stored 3 f 4 Potential difference 4 fawaid

The gap between the plates of a paralle I plate capacitor of area A and distance between plates d is filled with a dielectric whose permittivity varies linearly from at one plate to 2 at the other The capacitance of capacitor is 80 8 8 A A C d A din 2 B D o A 2d 80 8 A din 2014

space between the plates of a parallel plate capacitor is filled with a dielectric whose dielectric constant varies with distance as per the relation K x K 2x a constant The capacitance C of this capacitor would be related to its vacuum capacitance Co as per the relation A C 6 c 2d In 1 K d 2d In 1 2d Ko Co Co B C D C d In 1 K d d In 1 Ko 2d Co Co 2014

A parallel plate capacitor is made of two plates of length width and separated by distance d A dielectric slab dielectric constant K that fits exactly between the plates is held near the edge of the plates It is pulled into the capacitor by a force au F where U is the energy of the capacitor when dielectric is inside the capacitor up to distance x see figure If the charge on the capacitor is Q then the force on the dielectric when it is near the edge is Q d A B 201 ED C K K 1 2d1 p D Q d 201 p Q w K 2d1 n K 1 1

Inside the plates of a parallel plate capacitor of area A distance d a dielectric slab of dielectric constant K is inserted battery of emf V is connected to the plates of the capacitor After a long time the battery is removed If the dielectric slab is now taken out of the capacitor calculate the work required to remove the slab A EAV 2Kd B 1 K AV 2Kd C K 1 AV 2d D K K 1 AV 2d

In the circuit shown the potential energy stored in the 20 F capacitor is ImJ Find the total potential energy stored in the two unknown capacitors A 0 5 mJ B ImJ C 2 5mJ D 3 5 mJ 20 F 5 F 30V

The capacitors C and C3 in the circuit shown carry 5uC and 15 C charge respectively If the capacitors C and C store equal potential energy find the emf of the battery A 6 67 V B 7 5 V C 8 33 V D 10 V C 2 F

In a parallel plate capacitor the region between the plates is filled by a dielectric slab The capacitor is connected to a cell and the slab is taken out While removing the dielectric A Some charge is drawn from the cell B Some charge is returned to the cell C The electric field between the plates is increased D The electric field between the plates remains unchanged

After the switch shown in figure A is closed there is current i through resistance R Figure B indicates current variation curves a b c and d for four sets of values of R and capacitanc A Ro and Co B 2Ro and Co C Ro and 2Co D 2Ro and 2Co Which set goes with which curve R E Figure A C HH a A b C c B d D a B b D c A d C a D b B c A d C a C b A c B d D Figure B

70 In the circuit shown below to have same pote points a and b a dielectric of constant K 2 should be completely filled in C 1 F a HH 1 C 4 F 11 1 C1 and C3 3 C2 and C4 b C 4 F C 4 F HH 2 C1 and C4 4 C2 and C3

3 4800 02 4 5800 52 3 4800 2 26 If current is passed through a spring then spring will 26 after fein 1 Expand 2 Compress 1 3 Remain unchanged 4 Data not sufficient 27 When a capacitor of capacitance C is charged by a battery of V volt then the ratio of energy stored in capacitor to the heat produced during charging is 1 1 1 2 1 2 3 2 L 4 1 10 28 Acylindrical metal wire of resistance 902 is stretched uniformly to tripled its length Its new resistance will be 1 27 Q 540 2 8102 4 144 2 9 L 9 l ga 27 Pe 10 28 1 venta 3 3rfaffer Cal a safer faren G 1 1 1 3 2 1 902 vfart est e wala wird er 200270 Visao

A parallel plate capacitor of separation d is deformed as shown with 1 1 d or d or d for the capaci tance to remain unchanged a 1 d l d c d l d l d d d d l d hd h h d b l d b d d d d do antog A zia A M 12 rob en

Test 4 Code A 7 In the circuit shown below if the tap key K is pressed at time t 0 then which of the following statements is false K ww 500 2 500 0 6 F 1000 1 At time t 0 current delivered by battery 4 mA 2 At time t x current delivered by battery 2 mA 3 At time charge on capacitor 6 C

5 A capacitor of capacitance C is charged up 90 V and then connected to an uncharged capacit of capacitance 2C The final potential differenc across each capacitor will be 1 45 V 3 90 V In a certain region 2 30 V 4 60 V potential is given

A parallel plate capacitor has a uniform electric fiell E in space between the plates If the distanc between the plates is d and area of the plate is the energy stored in the capacitor is 1 Ad 2 4 E 3 E Ad 60

In the arrangement of parallel plate capacitor shown in figure dielectrics identical shaped with dielectric constant k 2 and k 3 are inserted If the capacitances are C and C respectively then ratio of C and C is A 2 K O 1 1 15 9 20 13 1 A 2 K 2 d 2 d 2

A battery of emf V volt resistance R and R a capacitance C and switches S and S are connected in an electrical circuit as shown in figure The capacitor C gets fully charged to V volt when T R S C ww R S A S and S are both closed B S and S are both open C S closed and S open D S closed and S open

8 In the circuit shown in figure K is open The 18 charge on capacitor Cin steady state is q Now key is closed and at steady state the charge on C 141 is q The ratio of charges ww THE 2 K alm 12 4 19 2R In the given circuit calculate the potential 19 Aku gaf K yeft bi fra starten cunfer START q1 af e 32 3 1 C STTIT q1 92 www R 92 2 K 2R 4 f after eft een 2 F instaford 73

1 Three uncharged capacitors of capacitance C C 11 and C are connected as shown in figure to one another and to points A B and D at potentials VA V and V Then the potential at O will be 2 3 B VA VB VD C C C VAC1 VBC2 VDC3 C C C VAVB VB VD VD VA C C C3 VA VB VD C C C C3 C C 2 In the circuit shown in the figure each capacitor 12 fra C C exigent 1 2 3 C seraftrat V V V B V VB VD C C Cs VAC VC VpC C C C3 VA VB VB VD VD V C C C VA VB VD C C C C3 C3C fax feat une entran

13 A parallel plate capacitor is charged by connecting it to a battery Which of the following will remain constant if the distance between the plates of the capacitor is increased in this situation 1 Point O Energy stored O Electric field O Potential difference O Capacitance

Consider the arrangement shown in figure The 10 fe fan fifay U total energy stored is U when key is closed Now the key S is made off opened and two dielectric slabs of relative permittivity K are introduced between the plates of the two capacitors The slab tightly fit in between the plates The total energy stored is now U Then the ratio of U U is e a 3 2K 1 K 1x 2 K K 4 K fear K fer fargarfiera aga fat fond au u t 1 2K 1 K 3 2 K K 4 T K U

a 9 kV 51 Four capacitors are connected to a 80 V supply as shown in figure Then the potential differe between the points X and Y is C 2 F C 4 F C 100 1 80 V VELGO V C C c 40 Y d 20 V

C C C C3 C3C1 In the circuit shown in the figure each capacitor 12 has a capacity of 3uF The equivalent capacity between A and B is 1 3 4 F 3 3 F 2 6 F 4 SUF ff unfre FAB e ka ar 1 3 4 F 3 3 F 2 6 F 4 5 F B

1 25 F 3 40 F Separation between the plates of a parallel plate 6 capacitor is d and the area of each plate is A When a slab of material of dielectric constant and thickness t t d is introduced between the plates its capacitance becomes Eo A d t 1 1 2 20 F 4 5 F Eo A d 1 1 1 2 EO A d t 1 COA 4 d t 1 1 25 F 3 40 F Ak qu gain vend f er ft d iz ft and suf unfar at and t X 1 3 2 20 F 4 5 F C A d t 1 2 CA 2 COA d t 1 i to A 4 d 1 1 4

An electrical technician requires a capacitance of 4 F in a circuit across a potential difference of 1000 V A large number of 2 F capacitors are available to him each of which can withstand a potential difference of not more than 200 V The minimum number of capacitors required are

Three uncharged capacitors of capacitane 1 C 2uF and C 3 F are connected as shown in figure to one another and to points A B and D poten tial V 10V V 25V and V 20 V Determine the A B D potential V at point O C 2MF C B A lov FC IMF LOV 3 F C3 11 D 20 V

A capacitor of capacitance 1 F withstands the maximum voltage 6 kV while a capacitor of 2 F withstands the maximum voltage 4 kV What maximum voltage will the system of these two capacitor withstands if they are connected in series 10 kV 2 12 kV 3 8 kV 4 9 kV

Phy Section A This section contains 35 SINGLE CORRECT TYPE questions Each question has 4 choices 1 2 3 and 4 out of which only Six identical capacitors each of capacitance Care connected as shown The equivalent capacitance between points A and Bis HH O 20 3 E

Three large identical conducting plates are placed at a distance d in air The space between the first two plates is filled completely with dielectric of dielectric constant 2 as shown The plates are given charges 7Q 3Q and 2Q respectively The outer plates are connected by good conducting wire through switch S When S is closed the charge that flows through switch is nQ Find the value of n 7Q 3Q 2Q LI K 2

32 A parallel plate capacitor of capacitance 90pF is connected to a battery of emf 20 5 V If a dielectric material of dielectric constant x 3 plates the magnitude of the induced charge will be a 1 2 nC b 0 3 nC c 2 4 nC is inserted between the d 0 9 nC

Discharging of a capacitor across three different resistance is given in figure then Qo 3 Question Type Multiple Correct Type 2 2 1 All three has equal heat loss 4 average life of discharging is maximum for 1 3 Third has least resistance initial rate of heat loss is

A parallel plate capacitor is charged with a battery of emf V volts After charging the battery is disconnected and the distance between the plates is increased to 1 5 times the initial value The new potential across the plates of the capacitor will become

Phy S This section contains 35 SINGLE CORRECT TYPE questions Each question has 4 choices 1 2 3 and A current is flowing through the loop as shown in figure below The magnetic field at centre O is O O O O R O 7 01 15R 16R 5 16R 7 17 15R 90 2R downward downward downward upward

A condenser of capacitance 10 F has been charg to 100 volts It is now connected to anot uncharged condenser in parallel The comm potential becomes 40 volts The capacitance another condenser is 1 15 F 2 5 F

Two capacitors of capacitance 2 F and 3 F are connected in series The outer plate of the 2 F capacitor is connected to 1000 V source and outer plate of 3 F is earthed The potential of inner plate of each capacitor is O 300 V O 500 V O 600 V O 400 V

The resultant capacitance of n condenser of capacitances C C2 Cn connected in series is given by 09 2012 20 C C C C 02 2 O C C 1 0 C O C C C Cn O C C C Cn

0 Four identical plates of area A and separation d are connected as shown in diagram Each plates of capacitor are in horizontal plane and P Q and R are three points between plates 1 P Q R 2 3 4 E 3mgd A Ife is in equilibrium between plates 2 and 3 then emf of battery is B Ratio of electric field at point P Q and R is 2 1 1 respectively C If plate 3 is shifted upward by d 2 ratio of potential difference between plate 1 and 2 and between 2 and 3 will be 8 3 D ratio of electric field between plate 2 3 and 3 4 will be 4 1 after the shift