Capacitors Questions and Answers

A capacitor of capacitance C 1uF can with stand maximum voltage V 6kV kilo volt and another capacitor of capacitance C 3 F can withstand maximum voltage V 4kV When the two capacitors are connected in series the combined system can withstand a maximum voltage of A LV 2 kV d 10 kV

of capacitance 5 F is connected in the figure The internal resistance of the cell is 0 5 Q2 The amount of charge on the capacitor plate is 6 A capacitor as shown a zero c 10 uC 12 www 5 F 222 2 5 V 12 wwww b 5 C d 25 C

A capacitance of 2 F is required in an electrical circuit across a potential difference of 1 0 kV A large number of 1 F capacitors are available which can withstand a potential difference of no more than 300 V The minimum number of capacitors required to achieve this is 1 32 3 16 2017 2 2 4 24 CV

In the circuit shown in figure the battery is an idea one with emf V The capacitor is initially uncharged Switch S is closed at time t 0 1 S CV 2 R 2 www R 2 www R 5R 2 www B The final charge Q on the capacitor is C 2 CV 3

19 24 A parallel plate capacitor is immersed in a liquid dielectric having dielectric constant as shown in the figure Find the force acting on a unit surface of the plate from the dielectric A BV 20 B E0 8 1 V 20 XE 8V 2d D E 1 V 2d

2 F 100 V Fig 25 25 3 F a the equivalent capacitance b the charge stored in each capacitor and

5 The adjoining figure shows two bulbs B and B resistor R and an inductor L When the switch S is turned off then R www 0000 B S HH 1 Both B and B die out promptly 1 2 Both B and B die with some delay 3 B dies out promptly but B with some delay

difference across the 100 20 Each capacitor shown in figure 31 E10 has capacitance of 50 F The emf of the battery is 50 V How much charge will flow through AB if the switch 8 is closed B 31 510

DAN TARGET PRE MEDICAL 2020 16 An air filled p constructed w Analysis through In the circuit shown below with steady current the potential drop across the capacitor must be R 1 when operat minimum pl Dielectric 1 0 38 c 3 0 45

CAREER INSTITUTE KOTA RAJASTHAN The plates of a parallel plate capacitor are given charges 4Q and 2Q The capacitor is then connected across an uncharged capacitor of same capacitance as first one C Find the final potential difference between the plates of the first capacitor liko o parallel plate capacitor in air in such

916 1 4 16 An uncharged parallel plate capacitor having a dielectric of dielectric constant k is connected to a similar air cored parallel capacitor charged to a potential difference V The common potential difference across them is 8 V k 1 11 6 2 2V k MF V k 1 kV 3 4 k 1 17 The capacitance between the points A and B of the combination is 3 V 20 A cap V with and a positi acros 1 3 21 Six REDMI NOTE

are placed concentrically in air B is given a charge Q and A is earthed The equivalent capacitance of the system is L q ca Internal 1 4 3 4 b H ab b a a to b A Va B Derivati clear 2 4 a b 6 b a 4 4 EO

6 A parallel plate separation d and capacitance C is filled 4 with four dielectric materials having dielectric constants k k k and k as shown in the figure below If a single dielectric material is to be used to have the same capacitance C in this capacitor then its dielectric constant k is given by NEET 2016 c d 2 A 3 A a k k k K3 3K4 2 b k k k kg 2K4 3 1 KA E A 3 3 k K K K3 1 1 1 1 k K K K3 2K4 K KA 3 A 3 K3 d 2 1

Q 30 A capacitor C is charged up to a voltage V 60 V by connecting it to battery B through switch 1 Now C is disconnected from battery and connected to a circuit consisting of two uncharged capacitors C2 3 0 F and C3 6 0 F through a switch 2 as shown in the figure The sum of final charges on C2 and C3 is JEE Main Online 2018 2 B 60 V A 36 C C 54 C 1 C B 20 C D 40 G C C3

A capacitor is charged by a battery and the energy stored is U The battery is now removed and the separation between the plates is doubled The energy stored now is U 1 1 2 3 DIN 2 3 2U 2 U 4 4U

4 Zero 29 Three different dielectrics are filled in a parallel plate capacitor as shown What should be the dielectric constant of a material which when fully filled between the plates produces same capacitance 1 4 3 5 K 67 Kdkd 72 72 2 6 4 9 32 While wo physics circuit a Unfortu your la a pote plenty in pla capa 3 33 A

Find the potential difference V Vb between the points a and b shown in each part of the figure 31 E14 12 V 2 F 3 2 V a 2 F HH 4 F 2 V a 4 F 2 F a 24 V b 4 F

What is the equivalent capacitance across the battery 79 A B C C 30 ALC 30 D 59 30 21 C 30 C C 2C B C HP C

Zoro 1V 1 5V 2V wwwwww 292 HH 2uF wwwwww 292 dy state

ratio of the current i through the cell at t 0 and t will be In the given circuit diagram the key K is switched on at t 0 The A 3 1 C 1 2 B 1 3 D 2 1 L HIC www B www 6R I a R fun K

26 Consider the situation shown in figure Find the heat developed in the connecting wires when the switch S is closed C is the capacitance of capacitor 1 CV GV CV CV V12 2 CV CV

25 Three capacitor C 2 F C 3 F and C3 4 Fare separately charged with battery of potential difference 40V 30V and 10V respectively and then disconnected After then they are connected to each other as C3 shown in figure A Final charge on capacitor C 800 13 800 13 380 13 D Amount of charge flow in circuit Zero B Final charge on capacitor C C Final charge on capacitor C3 C C C C

Each of the plates shown in figure has surface area A on one side and the separation between the consecutive plates is d The emf of the battery connected is E The magnitude of charge transferred through the battery is 1 A A A d 3 AE 2d A A dd A E 2 d AE 3d

159 A capacitor of capacitance C has initial charge Q and connected to inductor L as shown at t 0 switch S is pressed The current through the inductor when energy in the capacitor is three times of the energy of the inductor is r 1 2 LC 2 JLC 20 3 LC 4Qo 4 JLC S 000000 L no 820 12 ca 0 M 3CL

47 Which of the following variation of energy with time is correctly shown If charge in capacitor varies as 0 0 in LC oscillation 1 O UE UE po T pan mm m AR 2T

A condenser of capacity C is charged to a potential difference of V The plates of the condenser are then connected to an ideal inductor of inductance L The current through the inductor when the potential difference across the condenser reduces to V is 1 2 3 C V V L C V V L C V 2 V L 1 2 1 2 C V V

A system of two capacitors is shown in the figure If Ve V 20 V then A If switch S is closed potential difference between plate A and plate B is 15 volt 20 B If all switches are closed QA 6 C If all switches are closed Vp V C and Qo 10 6 volt 10 3 10 C 10 C S HC S A2 FB D If all switches are closed energy loss in the circuit is 625 3 3 HJ C D

Two identical capacitors C and C of equal capacitance are connected as shown in the circuit Terminals a and b of the key k are connected to charge capacitor C using battery of emf V volt Now disconnecting a and b the terminals b and c are connected Due to this what will be the percentage loss of energy a k b TC C TC 22

2018 A capacitor is charged by a battery The battery is removed and another identical uncharged capacitor is connected in parallel The total electrostatic energy of resulting system a decreases by a factor of 2 b remains the same c increases by a factor of 2 d increases by a factor of 4 NEET 2012

A 100 W resistance and a capacitor of 100 W reactance are connected in series across a 220 V source When the capacitor is 50 charged the peak value of the displacement current is NEET Phase 2 2016 2 11 A 4 115 A 1 2 2 A 3 44 A

A parallel plate capacitor of capacitance 5 F is connected to a battery of emf 6 V The separation between the plates is 2 mm a Find the charge on the positive plate b Find the electric field between the plates c A dielectric slab of thickness 1 mm and dielectric constant 5 is inserted into the gap to occupy the lower half of it Find the capacitance of the new combination d How much charge has flown through the battery after the slab is inserted

4 The capacitance between the adjacent plates shown in figure 31 E20 is 50 nF A charge of 10 C is placed on the middle plate a What will be the charge on the outer surface of the upper plate b Find the potential difference developed between the upper and the middle plates Di 21 590

There are two conducting spheres of radius a and b b a carrying equal and opposite charges They are placed at a separation d a and b The capacitance of system is 1 3 4 a b d 4 a 1 1 1 1 b 2 4 4 1 1 1 ab d 4 E 1 1 2

A capacitor is made of two square plates each of side a making a very small angle a between them a shown in figure The capacitance will be close to L 2 5 8E 1 3 Eo q d Eo q d aa 1 2d aa d 2 4 Eo a d Eo a d 1 aa 4d 3 a 22

7 A capacitor is made of a flat plate of area A and a second plate having a stair like structure as shown in figure 31 E9 The width of each stair is a and the height is b Find the capacitance of the assembly b

7 Initially S is connected to 1 as shown in the figure and then S is also connected to 2 Due to 2nd connection some extra charge redistribution of charge flows in the circuit For this situation mark out the correct statement s 10V A Due to 2nd connection work done by the battery is 200 J B Due to 2nd connection charge flowing through X in the direction shown is 10 J C Due to 2nd connection thermal energy dissipated in the circuit is 50 J D All of the above 10 F 5 F X 10

Three identical conducting plates are arranged as shown in figure and they are given charges as indicated When switch S is closed the amount of charge flown through the switch is 30 C 2d d HHH 20 C Jos 70 C

44 A parallel plate capacitor of capacitance 90 pF is connected to a battery of emf 20 V If a dielectric material of dielectric constant K 5 is inserted between the plates the 3 magnitude of the induced charge will be a 1 2 nC c 2 4 nC Evo JEE Main 2018 b 0 3 nC d 0 9 nC

The capacitor each having capacitance C 2 F are connected with a battery of emf 30 V as shown in figure When the switch S is closed Find S the C C 10 HH 30 V 1 I C a the amount of charge flown through the battery b the energy supplied by the battery c the heat generated in the circuit the switch S

Figure shows plots of charges versus potential difference for three parallel plate capacitors which have the plate areas and separations given in the table Which of the plots goes with which of the capacitors Capacitor 1 2 3 Area A 2A A C Separation d d 2d

The area of each plate of a parallel plate capacitor is A and separation between plates d The space between the plates of capacitor is filled with a non conducting material whose dielectric constant varies linearly along the separation between plates from a value K to 10K Capacitance of the capacitor is nearly K K A d 2 KEA 1 8 0 2 4 KA d K A 4 5 6

16 A spherical cell has a radius of 100 m Its membrane has a specific capacitance of 1 0 F cm and a leakage resistance of 2000 cm A current of strength 0 0005 A is introduced intracellularly and flows outward to a distant grounded electrode in the surrounding uniform unbounded medium The pulse duration is 2 msec Calculate and plot the transmembrane potential for the period 0 5 msec

5 Figure 5 shows a system of capacitors where the potential difference across ab is 38 0 V a What is the equivalent capacitance of this system between a and b b How much charge is stored by the system c How much charge does the 18 0 nF capacitor store d What is the potential difference across the 10 0 nF capacitor 18x7 5 119 29 25 5 a 7 5 6 5 18x7 51 a Figure 5 7 5 nF 18 0 nF 30 0 nF 10 0 nF HHHH 46 6 5 nF b

Two capacitors C 4 61 F and C 14 0 F are connected in parallel and the resulting combination is connected to a 9 00 V battery a Find the equivalent capacitance of the combination HF b Find the potential difference across each capacitor V V V V Find the charge stored on each capacitor C C 21 Q2 Watch H

Consider the combination of capacitors shown in the diagram where C 3 00 F C2 11 0 F C3 3 00 F and C4 5 00 uF Figure 1 gure C C 11 1 of 2 Part A Find the equivalent capacitance CA of the network of capacitors Express your answer in microfarads View Available Hint s CA AEO

Enter the circuit below that is not equivalent to the circuit above M Select one a c O b b O c d H a www b m WWW m d

The circuit in the figure below contains a 90 0 V battery and four capacitors In the top parallel branch there are two capacitors one with a capacitance of C 5 00 F and another with capacitance of 6 00 uF In the bottom parallel branch there are two more capacitors one with a capacitance of 2 00 F and another with a capacitance of C 7 00 F C HF 2 00 F UF 6 00 uF 90 0 V C a What is the equivalent capacitance in F of the entire circuit b What is the charge in C on each capacitor on C 1 HC on C on the 6 00 F capacitor on the 2 00 uF capacitor UC C HC c What is the potential difference in V across each capacitor across C V across C V across the 6 00 F capacitor V across the 2 00 uF capacitor V

Find the charge on each of the capacitors in the figure below 24 0 V 1 0 F capacitor 5 0 F capacitor 8 0 F capacitor 4 0 F capacitor 1 00 F 8 00 F 9999 5 00 F 4 00 F ST

ther At time t 0 the capacitor is connected in series to two ammeters and a light bulb Immediately after the circuit is closed the ammeter connected to the positive plate of the capacitor reads Ip and the ammeter connected to the negative plate of the capacitor reads IN Figure 1 Each ammeter reads positive if current flows through the circuit in a clockwise direction from the to the terminal of the meter igure g 1 q 1 Ip A 1 of 1 Submit Correct Part D Previous Answers Light bulbs are often assumed to obey Ohm s law However this is not really true because their resistance increases substantially as the filament heats up in its working state A typical flashlight bulb at full brilliance draws a current of approximately 0 5 A when connected to a 3 V voltage source For this problem assume that the changing resistance causes the current to be 0 5 A for any voltage between 2 and 3 V Suppose this flashlight bulb is attached to a capacitor as shown in the circuit from the problem introduction If the capacitor has a capacitance of 3 F an unusually large but not unrealistic value and is initially charged to 3 V how long will it take for the voltage across the flashlight bulb to drop to 2 V where the bulb will be orange and dim Call this time thright Express bright numerically in seconds to the nearest integer View Available Hint s tbright Submit VAZO S

capacitor at the time t 45 s is C 3 F E Zero D 9 82 C 9 50 B 8 65 A 6 32 In the circuit shown the switch S has been closed for a long time The value of voltage V in volts across the capacitor is a 12 b 3 1 3x106 c 15 d 5 e 10 15V IMQ dul 4MQ b 10 F 4MQ In the above question the charge on the capacitor is Q0 and then the switch S is opened at time t 0 the correct equation for the variation of charge with time is A Q Qoe t 80 B Q Qoe t 20 C Q Qoe t 30 D Q Qo 1 e t 80 E Q Qo 1 e t 20 2 bat