Current Electricity Questions and Answers

10 Four conductors of resistance 4 3 9 and 6 ohm are connected in AB BC CD and DA arms of a Wheatstone bridge The bridge can be balanced by connecting 1 3 ohm in series with 3 ohm conductor 2 4 ohm in parallel with 4 ohm conductor 3 either 1 or 2 4 neither 1 nor 2

In above question if resistance of meter bridge wire is 10 mega cm then the value of current is In the given circuit a meter bridge is shown in balanced state The value of resistance of the resitor marked as X is X 60 in 40 cm 60 cm

12 Switch S is closed at t 0 in the circuit shown The change in flux in the inductor L 500 m from t 0 to an instant when it reaches steady state is 592 a 2 Wb c 0 Wb 20 VT 592 eeee 500 mH St 0 592 10 V J 50 F b 1 5 Wb d None of these 304 6

Please give explaination and step by step solution with di agram and reason especially right most ckt In the circuit shown in figure calculate the ratio of current 1 12 is 252 492 www 2023 1 892 892 2 3852 16V 352 www Question Type Single Correct Type 8V 192

In the figure shown the numbers indicate the values of resistance in ohm The equivalent resistance of the combination across AB is A 3 17 2 www 2 3 2 2 www N B 3 17 A B C 2 wwww 2 3 17 2 2 2 www D 2 3 17

16 There are n cells each of emf E and internal resistance r connected in series with an external resistance R One of the cells is wrongly connected so that it sends current in the opposite direction The current flowing in the circuit is a c n 1 E n 1 r 2 n 2 E nr R b d n 1 E nr R n 2 E n 2 r R

94 While connecting 6 cells in a battery in ser a tape recorder by mistake one cell is connected with reverse polarity If the effective resistance of load is 24 ohm and internal resistance of each cell is one ohm and emf 1 5V the current devlivered by the battery is 10 1A 2 0 2A 3 0 3A 4 0 4A

1 4F 3 F 4 as its leaves A charged gold leaf electroscop apart by certain amount having enclosed air When the electroscope is subjected to X rays then the leaves 1 Further dilate 2 Start oscillating 3 Collapse 4 Remain unaltered 2 2F F LIN 2 positive charges are fixed at points a 0 and a 0 on the x axis An opposite charge q at rest is released from point Q a on 1 Decreases 2 Increases 3 Remains uncl 4 Increases if decreases if 19 Three charges 20 ne of length from one end order to make 1 q q 3 A particle o moving aro 2

84 A wire of resistance 0 25 ohm is first connected to a cell of internal resistance 0 50 ohm and then to a combination of 10 such cells in parallel Find the ratio of currents in the two cases 1 1 22 3 4 3 1 5 4 2 5

A 10 m long potentiometer wire is connected to a 23 battery having a constant voltage in the primary circuit A cell of unknown emf is balanced at 5 5 m length of the wire If the length of the potentiometer wire is reduced to 8 m then the new balancing length will be 1 5 5 m 2 4 4 m 31 65m 4 75m fauna 10 ford fed alccal f det mufaa ufua get hi 5 5 Land farga anser gioia san ti af a and at a tigern a 1 5 5 m 3 65 m 2 4 4 m LAY

2 A battery of e m f 2 2 volt and internal resistance 1 2 ohm is connected to a potentiometer wire of length 10m and resistance 9 8 ohm Find the potential drop per cm of length of the wire 1 0 196 m V 2 9 16 m V 3 19 6 m V 4 1 96 m V

Three cells each of e m f 1 5 volt are first connected in series and then in parallel to an external resistance The currents obtained in the two cases are respectively 1A and 0 36 A Calculate the external resistance 1 1 25 Q 3 4 125 2 2 3 26 4 2 235 S

A bulb is first connected across a 10 V DC supply and then a 20 V DC supply The ratio of power dissipated in the two cases will be resistance is constant 1 2 1 4 2 3 Your virus Mc lar ha Let A

180 Figure shows a circuit with three ideal batteries in it The circuit elements have the following values 13 AVB ww R 12 R www www R R TAVB a 0 50 A 0 25 A 0 25 A b 0 25 A 0 50 A 0 25 A c 0 50 A 0 50 A 1 0 A d 0 25 A 0 50 A 0 25 A A R i 13 AVB 3 0 V AVB 6 0 V R 2 092 R 4 0 2 AVB The currents i 2 and is as shown in the circuit have the values

a 0 25 92 internal res b 0 95 2 2 In an ammeter 0 2 of main current passes through then the resistance of ammeter will be the galvanometer If resistance of galvanometer is G CBSE AIPMT 2014 500 d 499 a 1 499 G of b 499 G 500 0 55 0 52 e Cles 1 G 500 d G d Rare

4 Lightning conductor A cell of constant e m f first connected to a 25 resistance R and then connected to a resistance R If power delivered in both cases is equal then the internal resistance of the cell is 1 R R 2 3 4 R R R R R R 2 4 frem for all and af affai 3takes fardu 1 R R 3 R R R R R R 2 fuc fl al

At temperature 23 C the resistance of a wire is 1000 The temperature at which resistance becomes 104 Q is nearly Given temperature coefficient of resistance of material is 1 5 10 4 C 1027 C 827 C 290 C 290 K

If two conducting wires A and B of same dimensions have electron density ratio 1 3 If their relaxation time is same then the ratio of resistance of A to resistance of Bis O 1 1 O 3 1 O 1 3

Two wires A and B of the same material having radii in the ratio 1 2 carry currents in the ratio 4 1 The ratio of drift speed of electrons in A and Bis 1 16 1 3 1 4 2 1 16 4 4 1

Choose the correct statement about the cell The terminal voltage of a cell is always greater than e m f The terminal voltage of a cell is always less than e m f The terminal voltage of a cell may be greater lesser or equal to e m f The terminal voltage of cell is always

4 In a circuit shown in figure the heat produced in 3 ohm resistor due to a current flowing in it is 12 J The heat produced in 4 ohm resistor is 1 2 J 22 wwwww 42 wwww wwww 3Q 2 4 J

Current flowing through a cylindrical conductor of area of cross section 1 mm is A If number of free electrons per m is 102 Then drift velocity of electrons is 2 5 x10 4 m s 25 x 10 4 m s 1 25 x 10 3 m s 2 5 x 10 3 m s

13 A piece of wire is cut into four equal parts and the pieces are bundled together side by side to form a thicker wire Compared with that of the original wire the resistance of the bundle is 1 The same 3 1 much 2 1 16 as much 1 as much

24 In a circuit shown in figure the heat produced in ohm resistor due to a current flowing in it is 12 The heat produced in 4 ohm resistor is 1 2 J 3 64 JI 222 wwww 492 www www 3Q 2 4 J 4 32 J

Hint nr and V E Ir 54 A cell of emf E is connected across a resistance r The potential difference between the terminals of the cell is found to be V The internal resistance of the cell must be To 2 E V V 1 2 r Hint V E IR and V Ir calculate R row maximum current from a combination of cells how should the cells be grouped 2 E V r E E V r V 3 4 E V r

A battery of EMF 10 V with internal resistance 12 is being charged by a 120 V d c supply using a series resistance of 10 22 The terminal voltage of the battery is 1 20 V 3 Zero 2 10 V 4 30 V

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

Consider the following diagram of a parallel circuit V h R1 R2 tot 0 65 A R 400 R 1600 Knowing that the total current splits according to resistance how much current will flow through each resistor 1 A

An application of Kirchhoff s Rules to the circuit shown results in the following system of equations Find the currents 1 12 13 12 1 13 5 41 31 0 10 312 713 0 Select the correct choice below and fill in any answer boxes in your choice OA The currents are 1 and 13 Type integers or fractions OB There are infinitely many solutions 792 ly 2435 10 V

In the given circuit diagram if ideal ammeter is connected between points A and B its reading is 5 A if ammeter of resistance 3 S2 is connected between A and B its reading is 3 A Reading of ideal voltmeter is 90 n volt if it is connected between A and B Find the value of n L www E2 R R www R A B R w R R

In the electrical circuit shown in figure the current through the 40 resistor is WB JEE 2013 a 1 A b 0 5 A c 0 25 A d 0 1 A 9VT 3Q 20 wwwwww 80 www ww 2022 0 5 A 20 40 R

wire of linear charge density 2 3 p and area of cross section A 4 mm2 is giver shown in figure When wire is pulled with sp 2 m s then current associated with it is dq 1 2 A 2 6 mA 3 6 A dL V

a moving coil galvanometer the deflection of the coil s related to the electrical current i by the relation MP PMT 1996 2000 03 RPMT 1997 MP PET 1999 ix tan 0 b ix 0 i x 8 d ix a

A 5 V battery with internal resistance 2 and a 2 V battery with internal resistance 1 are connected to a 100 resistor as shown in the figure P2 5V 202 The current in the 10 a 0 03 A P to P c 027A P to P www 1092 2V f P resistor is 12 AIEEE 200 b 0 03 A P to P d 0 27 A P to P

4 5 A 67 A standard 100 watt bulb is connected in parallel with 1000 watt heater This arrangement is connected to 220 V mains supply What will happen if bulb is switched off 1 The current through the heater will increase 2 The current through the heater will decrease 3 The current through the heater will remair unchanged 4 The current in the heater will be zero 011 47623456

45 Assertion A The current carrying circular copper coil kept in de a uniform magnetic field experiences maximum torque when its plane makes an angle of zero degree with the direction of the magnetic field Reason R The torque experienced by the current carrying coil inside a magnetic field is T mXB where symbols have their usual meaning

4 Five equal resistances each of resistance R are shown in the figure A battery of V volts is connected between A and B The current flowing in AFCEB will be CBSE PMT 1995 2004 KCET 2002 BHU 2006 MP PET 20131 a b c d 3V R R V 2R 2V R D R wwwwww ww R C www R R www ww A R B E

Resistors of 1 2 3 ohm are connected in the form of a triangle If a 1 5 volt cell of negligible internal resistance is connected across 3 ohm resistor the current flowing through this resistance will be KCET 2009 a 0 25 amp c 1 0 amp b 0 5 amp d 1 5 amp

When a voltmeter and an ammeter are connected one by one across the terminals of a cell respectively measures 5 V and 10 A Now all meters are removed and only a resistance of 2 2 is connected across the terminals of the cell The current flowing through this resistance is 1 7 5 A 2 5 0 A 3 2 5 A 4 2 0 A

3 For a cell the terminal potential difference is 2 2 V mwhen circuit is open which reduces to 1 8 V when it is connected to a resistance of R 5 then internal resistance of the cell is S D 10 22 or 1 9 ON 9 2 10 3 11 12 2 3 4 579 C 7 NODE02 BOAH BO TARGET PHY ENG MODU

24 n identical cells whether joined together in series or in parallel give the same current wher connected to an external resistance R The interna resistance of each cell is 1 r nR 2 r R 3 r R 4 r n R

PROBLEMS 1 How many neutrons are contained in 2 kg Mass of Ans 1 198 x 1027 one neutrons 1 67 x 10 27 kg 2 How many electrons mass 9 1 x 10 31 kg would balance one proton mass 1 67 10 27 kg Ans 1835 3 How many electrons should be added into a body to make it heavier by 5 nanogram Mass of one Ans 5 49 x 1018 electron is 9 1 x 10 31 kg 4 Convert a velocity of 20 m 8 1 in kilometre per hour Ans 72 km hr 5 Convert an acceleration of 50 kilometre per hour Ans 0 003858 m 8 21 into metre per sec 6 Convert an acceleration of 20 ms 2 in to kilometre per hour Ans 2 592 x 105 km h 2 7 How many metre are there in one i Gigametre iii Hectometre ii Femtometre iv Exametre v Nanometre vi Picometre Ans i 10 ii 10 15 iii 102 iv 1018 v 10 9 vi 10 8 How many gram are there in one i Teragram ii Microgram iv Petagram iii Attogram v Decagram vi Centigram Ans i 10 2 ii 10 6 iii 10 18 iv 1015 v 10 9 vi 10 21 9 How many centimetre are there in one i Fermi Micron iii v Astronomical unit ii Angstrom unit iv Light year Ans i 10 13 ii 10 8 iii 10 4 iv 9 5 1017 v 1 496 x 1013 are there in a mass of 2 Ans 2 x 1027 ng 10 How many nanogram exagram 11 What is the relation terametre 12 How many picometre are gigametre 13 Obtain a relation between between femtometre and Ans 1 fm 10 27 Tm contained in one Ans 1024 microsecond and

15 The equivalent resistance of four resistors joined in parallel is 30 2 The currents flowing through them are 4 2 4 3 and 2 3 amperes Determine the value of each resistor Ans 60 120 180 and 360 16 Find the current supplied by the battery Ans 5 A 852 mu

c A copper wire is quadrupled in length and tripled in diameter How does its resistance change The resistance of the wire is 4 9 times the original resistance The resistance of the wire is 3 4 times the original resistance The resistance of the wire is 4 3 times the original resistance The resistance of the wire is 9 4 times the original resistance

Four cells of emf 1V 2V 3V and 4V are connecte in parallel as shown If their internal resistances are respectively 192 19 19 and 292 then the current through the external load resistance R is EV a Ea ff i Feff Req 1 2A 3 2 A www 1V 12 H www 192 2V www H 192 3V 4V www 29 wwww R 2 92 2 4 7 2 A A

In an AC circuit consisting of a coil and a bulb how will the brightness of the bulb change if the frequency of source is increased a No change c Decreases b Increases d First decreases then increases

If the current travels before most of it have leakage out through membrane for unmyelinated axon is 0 03 cm then the radius of the axon is Rm 0 2 02 m pa 2 2 m and Cm 10 2 F m O O 5 m 7 2 m 3 2 m 12 8 m 1 8 m

The circuit diagram in figure shows three resistors 2 ohm 4 ohm and R ohm connected to a battery of e m f 2 V and internal resistance 3 ohm If main current of 0 25 A flows through the circuit find a the p d across the 4 ohm resistor b the p d across the internal resistance of the cell c the p d across the R ohm or 2 ohm resistor and d the value of R 0 25A 202 www RQ 2 V 4 0 www

Question 1 If in any circuit it consists of basic elements such as resistance inductance and capacitance Then by considering all paramete derive the relation of voltage and current for inductor element Ise the editor tp format your answer

3 A heater rated for 1000 W at 100 V is used in the circuit having a 100 V supply If the heater operates with a power of 62 5W then the value of R is 1X10 5 1 2 50 www 102 100V HEATER R 2 2092 viso A