Current Electricity Questions and Answers

Consider a circuit as shown in figure Then choose correct statement s 20 30 wwwww 50 10V 402 60 If 40 resistance is shorted resistance less wire connected in parallel to it the current through battery will increase If 402 resistor is shorted the current through 50 resistance will decrease O If instead of 40 50 resistor is shorted current through battery will decrease If instead of 40 30 resistor is shorted current through battery will decrease

Find the current through the 502 resistor if the voltage drop across 192 resistor is 3 V A IA B 1 33 A C 1 67 A D 2A 192 www 592 wwwww wwww 1002 2012

2 In the given circuit current I is independent of value of resistance Rs Then which of the condition must be satisfied A R R4 C R3R6 R R3 R R4 B R R3 R6 R R4 D R R3 R6 R R R4 R www R R wwww R R ww R

Q62 Three resistors each of 2 ohm are connected together in a triangular shape The resistance between any two vertices will be 1 4 3 ohm 2 3 4 ohm 3 3 ohm 4 6 ohm 1 85 From NCERT PMT 1983 2 3 4

Q63 There are n similar conductors each of resistance R The resultant resistance comes out to be x when connected in parallel If they are connected in series the resistance comes out to be 1 x n 2 n x 3 x n 4 nx 1 81 From NCERT PMT 2004 2 3 4

Q7 The equivalent resistance between points A and B in the circuit shown in the figure is 1 6R 2 4R 3 2R 4 R R R R 82 From NCERT R R R B 4

Two resistances are joined in parallel whose resultant is ohm One of the resistance wire is broken and the effective resistance becomes 20 Then the resistance in ohm of the wire that got broken was 1 3 5 2 2 3 6 5 4 3 1 2 3 4

In a hydrogen discharge tube it is observed that through a given cross section 3 13 x 1015 electrons are moving from right to left and 3 12 x 1015 protons are moving from left to right per sec What is the electric current in the discharge tube and what is its direction 1 1 mA towards the right 2 1 mA towards left 3 2 mA towards left 4 2 mA towards the right 1 2 3 4

Q55 A resistance R is stretched to four times its length Its new resistance will be 1 4 R 2 64 R 3 R 4 4 16 R 1 2 3 4

9 The three resistances of equal value are arranged in different combinations shown below The current entering from the left is same in all cases Arrange them in increasing order of power dissipation www www wwwwwwwwwwww III A III II IV I C I IV III ll www II www IV B II III IV I D 1 III II IV

A Q4 Two battries of emf 1 2 and internal resistance r r2 as shown in figure The effective emf of the circuit acr 1 1 2 3 4 1 1r1 2r2 r r E1r2 2r1 r r2 E1r2 2r1 r1 x r2 E1r1 2r2 r1 r2 1 11 2 B Subtopic Grouping of Cells 12 3 From NCERT 4

3 After the switch is closed the current will increase in which resistor s 252 352 492 552 A 192 B C D E 10 20 30 40 Lit

270 Four wires of equal length and of resistances 10 ohms each are connected in the form of a square The equivalent resistance between two opposite corners of the square is 1 10 ohm 2 40 ohm 3 20 ohm 4 10 4 ohm

Equivalent resistance between A and B will be ww 3023 A 352 302 352 1 1 2 ohm 2 18 ohm 3 6 ohm 4 3 6 ohm 30 352 352 2 ihtonio Co bination ww B 352 3 Rogietora I 4

The equivalent resistance of resistors connected in series is always 1 Equal to the mean of component resistors 2 Less than the lowest of component resistors 3 In between the lowest and the highest of component resistors 4 Equal to the sum of component resistors 1 2 3 Subtopic Combination of Resistors I 4

20 The resistance of the resistor shown below is De Violet Green Orange Gold 1 75 x 10 2 5 3 75 10 10 2 74 x 10 2 5 4 76 x 10 2 5

16 The current through the 2 2 resistor in the circuit shown below is 5 volt 1 3 A from a to b 2 3 A from b to a 3 2 A from b to a 4 1 A from b to a 10 volt 192 102 b 2 N

Q3 If a resistance coil is made by joining in parallel two resistances each of 2012 An emf of 2V is applied across this coil for 100 seconds The heat produced in the coil is 1 20 J 2 10 J 3 40 J 4 80 J 1 2 3 4

15 14 Two capacitors G and C C C are connected in series and joined to a battery as shown in the figure C The plot which shows correct variation in potential as one moves from left to right on the branch containing the capacitors is S r

Two long conducting bars P and Q are fixed parallel to each other in a horizontal plane some distance apart On these bars two parallel Jumpers J and J each of resistance R are arranged at seperation x as shown in the figure The Jumpers can slide on the bars with out friction At some point of time a uniform vertical magnetic field is switched on field strength is B Find final seperation between the Jumpers The force between the Jumpers due to their currents is negligible as compared to the force of interaction between current in the Jumper and the magnetic field coefficient of restitution between Jumpers is 0 5 B w x C 2x0 3 D NX

35 The current through the external resistance R 402 as shown in the following circuit is 10 V 202 1 Zero 3 5 A ugh Work 20 V ww 4Q ww R 4Q 2 2 5 A 4 8 A

sphere B made of n size If charge on ers of a 27 The energy stored in 2 F capacitor as sh the circuit in steady state will be 1 4 J 3 0 5 J 4 V HAV F 2 F wwwww 132 152 ww 202 www 2 2 J 4 1 J

36 Consider the following colour coded carbon resistor The resistance of this resistor is Violet Gold Yellow Red 1 47 10 5 3 81 10 2 20 h 2 47 10 2 10 4 80 10 5

13 2 In a potentiometer setup when a secondary cell emf 2 V is balanced balance length of 10 cm obtained If another secondary cell of emf 4 V connected in series with initial secondary cell same polarity the new balance length will be 1 10 cm 2 20 cm 3 30 cm

34 The power dissipated across the 302 resistor in the circuit shown is 40 4A JEF 1 30 45 W 302 www www 80 192 ww 2 21 33 W 4 2 W WWW 1622

3 8 A 4 6 A 3 A network of uniform wires is used to form a hexagon of each side 2 cm The resistance of the wires per unit length is 4 2 cm The net resistance across any two adjacent vertices is 1 48 2 15 Q 3 10 Q 4 6 67 2

8 V 6 V F 292 ww 292 www R www 1 7 A 2 10 A 3 2 A 4 8 A 13 When a metal conductor connected to right gap of meter bridge is heated the balancing point from left end NCERT Pg 120 1 Shifts towards left 2 Shifts towards right 3 Remains unchanged 4 Shift to zero position 14 Resistance P Q S and R are arranged clockwise cyclic order to form a wheatstone bridge The ratio of electric power consumed in the branches P Q and R S is INCERT Pg 109 1 1 1 ical IIT sh andatio 15 A battery of e m f 5 V and negligible internal resistance is connected across the diagonally opposite corners of a cubical network consisting of 12 resistors of network each of resistance 1 2 The current along one edge of the cube is NCERT Pg 116 1 1 A 2 2 A 3 3 A 4 4 A A Four arms of wheat stone bridge have the following resistances AB 60 2 BC 100 CD 60 2 DA 12 2 A galvanometer of 15 2 is connected across BD Calculate the value of additional resistance connected across CD to balance the bridge NCERT Pg 119 1 12 02 3 182 60 2 HH 5 V 1292 NCERT Maps 100 2 G 150 60 2 2 150 4 30 2

Two wire A and B of copper have equal masses and the lengths are 10 cm and 20 cm respectively If resistance of A RA be RA and B be RB then the value of is RB 1 21 12 2 2 3 1 1 4 4 4 1 2 3 4

A B and C are voltmeters of resistances R 1 5 R and 3 R respectively When some po tential difference is applied between X and Y the voltmeter readings are VA VB and Vc respectively B A A VA VB VC B VA VB VC C VA VB VC D VB VA VC

In the circuit shown in the figure the effective resistance between A and B is 1 20 2 40 3 6 4 80 1 652 852 42 8 52 2 652 www 402 B 3 4

Determine the Thevenin equivalent circuit shown in the figure as seen by the R 9 22 resistor Then calculate the current flowin through the R 9 Q resistor 4 A www 10 92 www 10 92 www R The current flowing through the R 9 Q resistor is A

5 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 ff VRI GIDI 1 E 21 050 215 V volt 2 0 1 5 1 0 0 5 21x 1 2 3 4 5 I amp 010 2 21x 050 ALE 21x

A current of 1 mA is flowing through a copper wire How many electrons will pass a given point in one second e 1 6 10 Coulomb 1 6 25 10 9 2 6 25 101 5 3 6 25 10 1 4 6 25 108 1 2 3 4

Q18 A battery has e m f 4V and internal resistance r When this battery is connected to an external resistance of 2 ohms a current of 1 amp flows in the circuit How much current will flow if the terminals of the battery are connected directly 1 1 Amp 2 2 Amp 3 4 Amp 4 Infinite

Q6 The equivalent resistance across AB is 1 2R 2 R 2 3 4R 3 4 3R 2 1 R H 2R R www www 2 by B 3 69 From NCERT 4

Q11 From NCERT If I be the current limit of a fuse wire of length I and radius r then select the appropriate relation 1 Ial 2 I a r 3 I a 1 4 I a r

Q14 The sensitivity of a potentiometer can be increased by 1 increasing the potential gradient 2 decreasing the length of potentiometer wire 3 decreasing the current in the potentiometer wire 4 all of these 1 2 3 4

Q20 Current I as shown in the circuit will be 1 10 A 2 20 A 3 3 A 4 20130 A 692 wwwww 392 69 69 wwwww 10 V 66 From NCERT

Q17 The drift velocity of free electrons in a conductor is v when a current i is flowing in it If both the radius and current are doubled then drift velocity will be 1 V 2 3 V 4 4 F 4

Q19 The equivalent resistance between A and B is Be 1 30 2 6 3 9 4 120 992 992 392 A 99 99 74 From NCERT

ilance shift hould 1 122 it circuit th cell mf emf 2 iternal oint of hen a circuit nifts to The 131 Current Electricity 20 Pick out wrong statement about the Kirchhoff s laws of electric circuit NCERT Pg 116 1 Outgoing currents adds up and are equal to incoming currents at a junction 2 Electric potential in electric circuit is position dependent Starting with any point if we come back to same point total potential change must be zero 3 Junction rule is based on conservation of energy law Bending or reorienting the wire does not the validity of Kirchhoff s 4 nge

e charge Q in order to make the net force on q to be zero PTIONS A 9 Solution Let the distance between the charges 4g and q be 1 4q x 0 kQq 3 Q F 1 2 x 1 2 For q to be in equilibrium fact 0 Q and q must be oppositely charged Let Fi and F is the force experienced by q due to charges Q and 4q respectively Thus Fi F k 4q q 12 q X 1 F F is the attractive force by Q and F is repulsive force by 4g 4kQq 4kq 2 Q 9 Since Q and q are of opposite nature Q 9

ABCD is a square where each side is uniform wire of resistance 12 Find a point E on CD such that if a uniform wire of resistance 12 is connected across AE and a constant potential difference is applied across A and C the points B and E will be equipotential

In the circuit shown in figure below the cells E and E have e m f 4 V and 8 V and internal resistance 0 5 ohm and 1 0 ohm respectively Then potential difference across cell E and E will be E 0 5 www 4 V ww 4 592 392 www ww 692 3 75 V 7 5 V 4 25 V 7 5 V 8 V 4 25 V 4 25 V 5 0 V 7 0 V 192 www

SolveLancer Test In the given figure are the bulbs are of same rating Which of the following statement is are correct for the given figure BA 13 If B fuses B glows dimmer ii If By fuses B glows brighter ii If B fuses B3 glows brighter iv If B fuses B glows brighter SolveLancer Test a iii iv b i iii c only 1 d i lv

2 What is the effect on null deflection of galvanometer when the radius of 1 point the wire is tripled a No change Ob Becomes half c Reduces by 1 3 Od Thrice the original value

Three identical voltmeters A B and Care connected as shown in a circuit If the readings of voltmeters A and B are 7 5 V and 5 V respectively then find the reading of voltmeter Cin volts wwww 902 14 52 A B O

5 A circuit has a section ABC as shown in figure If the potentials at point A B and C are V V2 and V3 respectively The potential at point O is A V V V C Zero B VV V R R R R R R V V D X X X R R R R R R

A network of nine conductors connects six points A B C D E and F as shown below The digits denote resistances in 22 Find the equivalent resistance between A and D A 2 B E ww 2 0 B 10 A www DX2 1 www 1 www 0 www F 5 www 2 C O D 11

2 9 In copper each copper atom releases one electron If a current of 1 1 A is flowing in the copper wire of uniform cross sectional area of diameter 1 mm then drift velocity of electrons will approximately be Density of copper 9 x 10 kg m Atomic weight of copper 63 1 10 3 mm s 3 0 2 mm s 2 0 1 mm s 4 02 cm la