Capacitors Questions and Answers

Calculate final charge on 1 F capacitor 6 C 1uF 10V 492 www 452 3 F 192 www

A charged capacitor is connected with a resistor After how many time constants does the energy of capacitor becomes 1 10 th of its initial value 1 2 3 3 0 69 2 1 15 4 None WODULF 041 3 C

5 38 A telephone wire of length 200km has a capacitance of 0 014 F per km If it carries an AC current of frequency 5kHz what should be the value of an inductor required to be connected in series so that the impedance of the circuit is minimum A 0 35 mH C 3 5mH B 35 mH D Zero

A 2 75 F capacitor is charged to 460 V and a 3 95 F capacitor is charged to 525 V 1 What is the voltage for each capacitor if plates of opposite sign are connected 2 What is the charge on each capacitor if plates of opposite sign are connected

The dimensions of RC is a square of time b square of inverse time uriens c time d inverse time 190

Two spherical conductors each of capacity C are charged to potential V and V These are then connected by means of a fine wire The loss of energy will be 1 zero Rober CV 3 CV 4 2CV Cv

In the circuit diagram shown in the adjoining figure the resultant capacitance between P and Q is a 47 F b 3 F c 60 F d 10UE P 12 F HH HH 2 F 3 F

A capacitor of capacitance C is charged to a potential V The flux of the electric field through a closed surface enclosing the capacitor is

2 1 A capacitor of 4 uF is connected as shown in the circuit Figure The internal resistance of the battery is 0 5 2 The amount of charge on the capacitor plates will be 4 F a 0 C a 166 2 5 V 292 10 Q2 b 4 C d 8 u C

A parallel plate capacitor is made of two square parallel plates of area A and separated by a distance d A The capacitor is connected to a battery with potential V and allowed to fully charge The battery is then disconnected A square metal conducting slab also with area A but d thickness is then fully inserted between 2 the plates so that it is always parallel to the plates How much work has been done on the metal slab by external agent while it is being inserted 1 A 1 3 4 d V 1 Eo A v2 2 d 2 4 10 AV 2 d 1 A v 4 d 5

44 In the circuit diagram shown all the capacitors are in mF The equivalent capacitance between points A B is in mF A o 1 14 5 3 3 7 8 10 HH HH OB 2 7 5 4 None of these

1 Q 7 Q If potential difference across AB is 5V find the charge on each capacitor 4 F 4UF 4 F H AUF B q Find the equivalent capacitance between A B What will be the change in its val is found between and B sen Answer key 4 8 F

An infinite ladder of capacitors each 1 F is made as shown in IT I figure The capacitance between A and B in F is A 1 C 1 6 ATTI B 1 3 D 0

4 10 5 F Equivalence capacitance between the points X and y in the circuit is i 2C 1 3 X 2 Y 5C 3 15 3C 5 capacitance of 10 uF is charged to a potential of 4 None of these 3

In the circuit as shown in the figure the maximum energy stored in capacitor is 6 216 mJ Then emf of the cell is 3 F 1 30 V 3R 3228 E R 2 20 V

12 Two identical capacitors A and B are charged to the same potential V and are connected in two circuits at t 0 as shown in figure 45 Q2 The charges on the C R A Figure 45 Q2 B AF C R b

charge on the 6 F capacitor in the circuit shown is A 90V B 1 540 C 9 F 6 F 12 F HH HH 2 270 C

In induction the charge induced in the near surface of a dielectric is 1 Equal and dissimilar 3 Lesser and dissimilar 2 Greater and dissimilar 4 Equal and similar

If an ac source is connected across ideal capacitor and current passing through it is denoted by curve a then instantaneous power is denoted by curve Doo b 1 c a d C e 2 b 8 t

4 In the circuit each capacitor has a capacity of 2 F Then the charge on each capacitor is A a 20 C c 30 C B 2 F HH 13 ix HE 2 F 10 VI 2 F HH 40 wwwwww 422 ww HI 2 F ww 402 www 102 8 8 C 4 C C Vii D

capacitance of the bigger drop compared to each individual drop is The capacitance of a spherical condenser is 1uF If the spacing between the two spheres is 1 mm then wh is the radius of the outer sphere When 2 x1016 electrons are transferred from one conductor to another a potential difference of 10 V appea Coment 3x106

A capacitor is having a capacity of 2pE Potential difference between plates of the capacitor is changing with a value of 10 2 V s The displacement current is 1 2A 2 3A 3 6A 4 9A

Example 41 The switch S shown in the figure is kept closed for a long time and is then opened at t 0 Find the current in the middle 10 S2 resistor at t 1 0 ms 25 F ww 10 S ww S

C Illustration 18 Twelve identical capacitors each of capacitance C are connected as shown in figure Find the effective capacitance between P and T T E24 2

12 Refer to the infinite network of capacitors shown in figure The capacitance of each capacitor is 1uF the equivalent capacity between A and B is a luF c OuF b2uF d HHHHH HHH 8 capacitors

The stratosphere acts as a conducting layer for the earth If the stratosphere extends beyond 50 km from the surface of earth then calculate the capacitance of the spherical capacitor formed between the stratosphere and earth s surface Take radius of earth as 6400 km

25 A capacitor of capacitance 1 F withstands a maximum voltage of 6 kv Another 2 F capacitor withstands a voltage of 4 kV If these two capacitors are connected in series what is the maximum withstanding voltage of this combination A 10 kV B 2 kV C 24 kV D 9 kV

In the given circuit ratio of charge on capacitor 2C and capacitor C in steady state is 1 1 1 2 2 1 3 1 2 R www C wwww 2R 2C HF wwww R wwww 2R

175 The capacitance of the capacitors of plate area A A A A at a distance d is a A EA d A A d A b d A d E A A

C 3uF and C 6 F are connected in series and charged by connecting a battery of voltage V 10 V in series with them They are then disconnected from the battery and the loose wires are connected together What is the final charge of each C 7 1 2 C 3 4 C 2 C 4 Capacitors

A capacitor C 3 F has an initial potential difference of 12 V and a second capacitor C 5 F has an initial potential difference of 10 V Find the final charges and potential differences for each if they are then connected with the followin poldrities for the plates like signs together b unlike signs together

Illustration 6 Two capacitors of capacitance C 6 0 09 F and C 3 0 09 F are connected in series Find the equivalent capacitance C with error Cz Solution 1 1 1 1 C C C Taking differential dC 1 1 3 6 dC dC C C C 2 0 05 F C 2 F dC 0 05 GC 3 C 6 bala OG DC AC A C G 1C C2 2 as per formulla of X ox n 2 qm bn 2 MD9 nob a b

3 In the given circuit the potential difference between A and B is 18 V and charge on 2 F capacitor is 24 C The value of C is A 6 F 2 F C HH B

For the arrangement of capacitors as shown in the circuit the effective capacitance between the points A and B is capacitance of each capacitor is 4 F A A 4 F C 1 F 4 F 4 F The work dono 4 F 4 F B B 2 F D 8 F 4 F 19 3508 docond 20 Be Bombe A A A 4 C C 1

1 60 F 2 30 F In the given network equivalent capacitance is 3 F is C 2 F AHHH 6 F 1pF 2uF 3 10 F 4 5 F the value of C So that an between points A and B 31 HH 12 F 2 F H 8 F F4uF B

55 The radius of the internal cylinder of a cylindrical air capacitor is r 1 5 cm and that of the external cylinder r 3 5 cm A potential difference of V 2300 Vis applied between the cylinders What velocity will be imparted to an electron from a distance of 1 2 5 cm to a distance of 1 2 cm along the cylinder axis under the action of the field of this capacitor a 1 5 x 107 m s c 2 5 x 107 m s b 1 5 x 10 m s d none of these

In Illustration 18 find the effective capacitance between P and V Solution Po If a battery be connected across the terminals P and V from symmetry V Vw and V V W

In the circuit diagram shown all the capacitors are in uF The equivalent capacitance between points A B is in F 6 AO 1 14 5 8 3 HH 10 7 HH 2 7 5 OB

Example 81 Figure 2 123 shows two identical capacitors C and C each of 1 F capacitance connected to a battery of 6V Initially switch S is closed After some time S is left open and dielectric slabs of dielectric constant x 3 are S 6V 1 F C 1 F C Fig 2 123 inserted to fill completely the space between the plates of the two capacitors How will the i charge and ii potential difference between the plates of the capacitors be affected after the slabs are inserted

In the following between A B is 1uF Find the value of 3 Just now 1 Ao t Bo 23 32 S F D 2 F C 1 F HK uF 2 6uF 2uF 12uF g 32 uF 23 HF 4 F B B 13 HF 3 UF 23 4 23 13 H

In the given circuit find potential at poin 1 3 4V 11 9V 11 V c 1 3V 2 11 4 None of these

In the circuit shown switch is connected to position 1 for a very long time What is maximum current through inductor when switch is taken to position 2 6V 1202 1 mot 0 10 netzib 2 C 50 F 1 1 5 A 2 3 A abnoosa L 0 8 mH 3 1 A 4 6 A for of 1 m fr Calcula distance screen 1 60 3 40 20 A un linea sho of e

The distance between the plates of a parallel plate capacitor is 0 05 m A field of 3 x 104 V m is established between the plates It is disconnected from the battery and an uncharged metal plate of thickness 0 01 m is inserted into the gap between the plates Find the potential difference of the capacitor i before the introduction of the metal plate and ii after its introduction What would be the potential difference if a plate of dielectric constant K 2 is introduced in place of metal plate

12 In the given circuit the charge on the plates of 1 uF capacitor when 100 V battery is connected to the terminals A and B will be AF 1 F A 2 F HH HH 3 F 21 FO B V

A parallel plate capacitor of capacitance C is connected to a battery and is charged to a potential difference V Another capacitor of capacitance 2C is connected to another battery and is charged to potential difference 2V The charging batteries are now disconnected and the capacitors are connected in parallel to each other in such a way that the positive terminal of one is connected to the negative terminal of the other The final energy of the configuration is A Zero B 25CV 6 3CV 2 C D 9CV 2

A thin metal plate P is inserted between the plates of parallel plate capacitor of capacitance C in such a way tha its edges touch the two plates The capacitance now becomes a C 2 c zero b 2C d

Choose the incorrect statement if the given network is in steady state A The P D across all capacitor equal 10V B The P D across all resistance equals zero C The charges on all the three capacitors are equal D The charge across 8 F capacitor is maximum among the three capacitors 2 F 8 F 502 4 F www 10V www 1002

For the circuit shown here the potential difference between points A and B is A 2 5 V B 7 5 V 6C ec3cc2c 10V to 2002 ww C 10 V D Zero hown The potential drop across the 7 F capacito

26 Find the equivalent capacitances of the combinations shown in figure 31 E15 between the indicated points 1 F F 4 F 3 F 12 2 F HH H 4 F J a 3 F H 4 F 1 F 4 F 5 F HH 8 F 1 F F 2 F 4 F 2 F 3 F 2 F er esint 4 F H 4 F 4 F 2 6 HEI 6 F 6 F 3 F W F 4 F 8 F IH 8 F 1 4 F ugod A

10 The minimum potential energy required to cause a spark is 10 mJ Assume that the capacita of the central part relative to ground is nearly 36 pF Calculate the potential energy stored in capacitor Take 3 A 1 8 mJ C 5 4 mJ B 3 6 MJ D 7 2 mJ