Current Electricity Questions and Answers

Twelve wires each having equal resistance r are joined to form a cube as shown in figure 32 E20 Find the equivalent resistance between the diagonally opposite points a and f a h b e d g

15 For a cell a graph is plotted between the potential difference V across the terminals of the cell and the current I drawn from the cell The e m f and internal resistance of the cell is E and r respectively A E 2 V r 0 5 S C E 2 V r 0 5 Q AV volt 2 0 1 5 1 0 B E 2 V r 0 42 0 5 D E 2V r 0 422 1 2 3 4

The resistances in the two arms of the meter bridge are 5 2 and R2 respectively When the resistance R is shunted with an equal resistance then new balance point is at 1 6 7 The resistance R is CBSE AIPMT 2014 A 1 A 1022 C 20 5 Q G RS B B 15 Q2 D 25 2 100 4

3 You are given resistance wire of length 50 cms and a battery of negligible resis tance In which of the following cases is largest amount of heat generated NCERT 74 a when the wire is connected to the battery directly 0 b when the wire is divided into two parts and both the parts connected to the battery in parallel c when the wire is divided into four parts and all the four parts connec ted to the battery in parallel d when only half of the wire is connec

28 Consider all batteries are ideal batteries Power developed in 2022 resistance is 20 V 40 220 23 1 100 W 3 180 W 10 V 1022 40 V 30 22 www 2 60 W 4 50 W 60 V 50 V

f a current is passed in a spring it O Oscillates O Remains unchanged Gets compressed

A small charged particle of mass m and charge q is suspended by an insulated thread in front of a very large conducing charged sheet of surface density of charge o The angle made by the thread with the vertical in equilibrium is 1 tan 3 tan oq 28 mg q 208 mg q m 30 2 tan 4 Zero 28 mg

59 The current in the circuit shown below is 1 1 A 6 V 4 492 www www 492 49 www www 42 wwww 29 2 2 A

The resistor in which the maximum heat is produced is given by B 30 D 120 A 20 C 452 492 69 12 Q2 3Q ww www 252

In an ammeter 0 2 of main current passes through the galvanometer If resistance of galvanometer is G the resistance of ammeter will be CBSE AIPMT 2014 500 499 G b G c G d G 499 500 500 499 5 A wire of resistance 402 is stretched to a

In the ladder network shown current through the resistor 3 is 4 A The emf V of the ideal battery Q is equal to 792 ww 802 C 50 www 603 192 30

5 What is current supplied by cell in above figure T 22 10V H 20 20 5 b A 4 c 5 A d 2

16 Figure shows a part of a closed circuit If the current flowing through it is 2A what will be the potential difference between points A and B 2A O A lv 2A www mm 1 2 1 4 S2 www 1 4 52 S O B

Figure shows two conducting thin concentric shells of radii r and 3r The outer shell carries charge q Inner shell is neutral When the switch is now closed the charge that will flow to earth from the inner shell is 1 olm 3 q 3r 2 2q 3

The current through a wire depends on time as 3t 2t 5 The charge flowing through the 2 of the wire in time from t 0 tot 2s cross section a 22 C c 18 C AV b 20 C d 5 C

The r m s value of current for one teric period in the above diagram which is plotted between i and t is A 1 2 A 4 2 3 2 2 A 0 4 4 10 1 2 A 1 4 2 2 A

18 A potential difference of 2 5 V is applied across the faces of a germanium crystal plate The face area of the crystal is 1 cm and its thickness is 1 0 mm The free electron concentration in germanium is 2 x 1019 m 3 and the electron and holes mobilities are 0 33 m V s and 0 17 m V s respectively The current across the plate will be 1 0 2 A 3 0 6 A at 2 0 4 A 4 0 8 A Jonaition 2 1 A 3 2 A 4 4 34 The c each back con

A and B are at the same potential 56 In the given figure a balanced Wheatstone bridge is shown Now it is disturbed by changing P to 15 2 Which of the following steps will not bring the bridge to balance again www wwww P 109 Q 100 92 15 1 Increasing Q by 50 2 3 Increasing S by 20 2 PR Hint www R 200 for balancing condition www S 200 92 2 Increasing R by 10 2 4 All of these

5 The value of drift speeds at cross sections 1 and 2 are V and V respectively in the conductor shown below in the shape of a truncated cone Which of the following is correct 1 V V 3 V V THHE 2 V V 4 Any of these

3 5 8 2 BEGINNER S BOX S respectively indicate inductance caporance and resistance Select the combination which does not have dimensions of frequency 1 1 RC Jav RA 1 JLC 4 CA A coil of 10 H inductance and 50 resistance is connected to 5 volt battery in series The current in ampere in circuit 2 seconds after switched is on 1 e 2 1 e An L R circuit consists of an inductance of 8mil and a resistance of 40 The time constant of the circuit is 1 2ms 2 12ms 3 32ms 4 500 s In an L R circuit time constant is that time in which current grows from zero to the value Where 1 is the steady state current 1 0 63 I 2 0 50 I g 3 0 371 4 1 An inductor of 20 H and a resistance of 10 2 are connected to a battery of 5 volt in series then initial rate of change of current is 1 0 5 amp s 4 0 25 amp s 2 2 0 amp s 3 2 5 amp s A coil of L 5x 10 H and R 18 2 is abruptly supplied a potential of 5 volts What will be the rate change of current in 0 001 second e 6 0 0273 1 27 3 amp sec 2 27 8 amp sec 7 the A coil of inductance 8 4 mH and resistance 602 the coil is 1 0A at approximately the time 1 500s 2 20s growth 3 2 73 amp sec 4 2 78 amp sec is connected to a 12V battery in series The girre 3 35ms 4 lis 1 2

A potential difference V is applied to a conducting wire of length I and diameter d How are the electric field E the drift speed vand the resistance R affected if i V is doubled ii I is doubled iii d is doubled

You are given several identical resistances each of value R 10 22 and each capable of carrying a maximum current of 1A It is required to make a suitable combination of these resistances of 5 92 which can carry a current of 4 A The minimum number of resistances of the type R that will be required for this job is CBSE AIPMT 1990 a 4 b 10 c 8 d 20

A cylindrical metal rod of length L and cross sectional area S is joined to an EMF source The drift speed of electrons in the rod is v If this rod is replaced by another rod of length 2L and cross sectional area 25 then drift speed of electrons in the new rod will be 1 VIN 2 3 2v 2 v 4 4v

W 2 resistance of circuit shown in figure between points A an 6 10 Q A WWW 10 Q Cowww 10 Q 10 Q ww www 10 Q O 2 20 92 10 Q WW B 10 2 Www D 10 Q

What is the drift velocity of electrons in a silver wire of length 1m having cross sectional area 9 5 x 10 7 m and carrying a current of 10A Given atomic weight of silver 108 density of silver 10 5 103 kg m charge of electron 1 602 10 1 C Avogadro s number 6 023 x 1026 per kg atom

A potention is potential gradient across the potentiometer wire k volts cm and the ammeter present in the circuit reads 1 0 A when two way key is switched off The balance points when the key between the terminals i 1 and 2 ii 1 and 3 is plugged in are found to be at lengths cm and l cm respectively The magnitudes of the resistors R and X in ohms are then equal to respectively WWW 11 P A R Holl 1 kl and kl 3 9 Q 15 2 k and kl

Initially the spheres A and B are at potentials V and VB When B is earthed the potential of A will be B 1 VA 3 2VA A a b 2 VA 2 2 4 VA VB

3V 252 For the resistance network shown in the figure choose the correct option s JEE 2012 Paper 1 4 12 292 S 252 49 1 wwww 12 wwwww 422 Shim 12 V 192 A The current through PQ is zero The potential at S is less than that at Q 202 Imm T 422 B I 3 A D 12 2 A

A ring is made of wire having a resistance Ro 120 Find the points A and B as shown in the figure at which a current carrying conductor should be connected so that the resistance R of the sub circuit between these points is equal to 8 302 a 45 12 8 b B CBSE AIPMT 2012 1 4 12 T

4 Calculate the current in a wire if 700 C of charge passes through it in 15 minutes 5 Electric potential at a point in an electric field is 05 Y whon 1 from infinit

If dissipation of same energy takes place in all three resistors R R and R3 then their value must be related as 1 R R R3 2 R R R3 3 R 4 R R3 and R R www R R3 and R 4R R 4 E

8 The dimensions of a block are 1 cm x 1cm x 100 cm If the specific resistance of the material is 3x 10 72m then the resistance between two opposite rectangular bases is a 3 10 2 c 3x10 50 b 3x10 72 d 3x10 0

D T Find the equivalent resistance of the circuit given 252 ww 192 B 602 D figure between the following point 492 www E 2023

26 A body cools from a temperature 37 to 27 in 10 minutes The room temperature is T Assume that Newton s law of cooling is applicable The temperature of the body at the end of next NEET Phase 2 2016 10 minutes will be 1 3 4I3 T 2 3 T 2 DIN 4 T

12 resistors arranged symmetrically in shape of bipyramid ABCDEF Here ABCD is a square Point E point F and center of square are in the same straight line perpendicular to the plane of square The resistance of each resistor is R E A D B blw A and B

In the circuit shown the battery the ammeter and the voltmeter are ideal Pick the correct choice s A B C D Power supplied by battery is 72 W Rate of heat dissipation in 302 resistance is 12 W The ammeter reads 4 A 3 The voltmeter reads 22 V 24V 12 40 V wwwww 252 wwww 452 352 852 652 www 492 A

130 The power dissipated in 3 92 resistance in the following circuit is a I W c 0 25 W 45 V 102 252 312 b d 69 452 40 0 5 W 0 75 W Karnataka CFT

Da Q10 alculate the heat develled when 3 A Corrient through an electric Iron box designed to work an 230v

A battery of 24 cells each of EMF 1 4 V and internal resistance 2 2 is to be connected so as to send maximum current through a resistor of 12 2 How should they be connected Find the strength of the current in each of the cells and the potential difference across the external resistance

57 In a network as shown in the figure the potential difference across the resistance 2R is the cell has an emf E with no internal resistance 1 2E 4E 2 3 4 E R ww 4R 2R E

Initially the switch S is open for a ling time Now the switch S is closed at t 0 R 20 R 20 C 1F and C 1F Then A The current through the wire AB at t 2 sec is 1 2e ampere B The current through the wire AB at t 2 sec is 1 e ampere C The charge on the capacitor C2 which was initially uncharged at t 2 sec is 1 coulombs 2e D The charge on the capacitor C at t 2 sec is coulombs 1 2e 2V R R www C B S C

Two cells having unknown e m f s E and E E E are connected in potentiometer circuit so as to assist each other The null point is obtained at 8 125 m from the higher potential end When cell E2 is connected so as to oppose cell E the null point is obtained at 1 25 m from same end Compare the e m f s of two cells Ans 1 364 E

JEE 1977 D 2 Two non physics students A and B living in neighboring hostel rooms decided to economies by connecting their bulbs in series They agreed that each would install a 100 W bulb in their own rooms and that they would pay equal shares of the electricity bill However both decided to try to get better lighting at the other s expense A installed a 200 W bulb and B installed a 50 W bulb Which student is more likely to fail the end of term examinations

charge crossed through a section of the wire in 3 Estimate the average drift speed of conduction electrons in a copper wire of cross sectional area 1 0 x 10 7 m carrying a current of 1 5 A Assume that each copper atom contributes roughly one conduction electron The density of copper is 9 0 10 kg m3 and its atomic mass is 63 5 amu

14 In the circuit shown A i 2A 10 2 B i 9 A wwwww 20 22 30 Q 60V C i 5 A D i 11A

Find equivalent resistance between A and B A R R ww R R R B

Q 1 A current of 1 2 x10 10 A flows through a wire of diameter 2 0mm Calculate the current density 3 8 x 105 Am

In the given ci zero deflection if A R F R 1 R R R R 2 R R R R4 3 R R R R gar WWW R R G will A

A resistance R and a nonlinear device D are connected with an ideal battery as shown in the given network Current I through the nonlinear device varies with voltage V across the device according to equation I kV2 Here k is a positive constant Find expression for the current in the circuit

Example 3 37 Find the current drawn from a cell of emf 2 and internal resistance 2 connected to the network given below D 122 12 tr ww 12 O 12 12 12 B C