Current Electricity Questions and Answers

All the resistors of the circuit in the figure have same resistance RS The current through the resistor AB is I V A C 6 R 6 V 7 R 1 V 7 R D zero B www B ww

A uniform wire of resistance 3652 is bent in the form of a circle The effective resistance between A and B is O is the centre of circle 0 130 B

70 The potential difference between the terminals of a cell is found to be 3 volts when it is connected to a resistance of value equal to its internal resistance The e m f of the cell is 1 3 V 3 1 5 V R tR J 2 6 V 4 4 5 Vjo

2 The effective resistance between B and C of letter A containing resistances as shown in Fig 2 24 is qnbsite 1092 www 1092 A www m 1002 www 10 2 10 2 F Amosios s

About internal resistance of a cell the correct statement is that it is 1 Constant for a given cell 2 Infinite 3 Finite and its value decreases with increase of time of use 4 Finite and its value increases with increase of time of use

27 Figure shows n batteries connected to form a circuit The resistance denote the internal resistance of the batteries which are related to the emf as r KE where k is a constant potential difference between the terminals of ith battery is E E A zero C r E wwwww Er 1 1 E none of these 1 E www 1 B Ei D T4 Eri E E E r E

In the given circuit the ammeter A and A are ideal and the ammeter A3 has a resistance of 1 9 10 2 If 2n sum of readings of all three meters is given by Ampere the value of n will be 27 A 10V 50 ov 1592

38 In the given circuit diagram the potential difference between A and B is HFW 192 6 V 1 3 V 3 6 V A 292 FM 3V 2 5 V 4 9 V 3 B 0 Jab interl resistan whichiga to VAB E

71 A current of 2 A is flowing through a cell of e m f 5 V and internal resistance 0 5 22 from negative to positive electrode If the potential of negative electrode is 10 V the potential of positive electrode will be 118 1 5 V 3 15 V 2 14 V 4 16 V

3 An electric bell has a resistance of 502 and requires a current of 0 25 A to work it Assuming that the resistance of the bell wire is 192 per 15m and that the bell push is 90m distance from the bell How many cells each of emf 1 4V and internal resistance 252 will be required to work the circuit A 3 D Can t be determined B 4 C 5 ront from A Thon

For different values of resistance R power consumptions in R are given Then which of the following values are not possible 4 V ww 19 sam R a 2 W b 5 W c 8 W 101 d 4 W

Two resistances r and r r are joined parallel The equivalent resistance R is such tha

What is the ratio of the readings of the ammeter A and A2 in the twork shown below 20 2 E 15 V 10 Q 50 4 3 S 3 TiOV www 10 2 502 aration 1 1

In the given circuit if power rating of heater is 1000 Watt at 100 Volt find the resistance R in figure so that heater produces power of 62 5 W a 502 c 100 1002 24 V Heater ww R b 752 d 82

21 A cylindrical wire is compressed in length by 10 The percentage decrease in the resistance will be a 16 c 20 b 19 d 25

CE0071 In the following circuit if V V 4 V then the 5 value of resistance X in ohms will be B 77 1 5 5 2 10 3 15 4 20 A www 102 2 V F w M 5 V ww 8 1 25 CE0072

ork shown the resistance between two adjacent junctions is R Equivalent resistance between point a and b is 1 3 7R 6 7R FR R R R R R a N R R b R3 R R 2 R www R 5R 6 5R FR

Twelve identical resistors are arranged on all edges of a cube Then find the equivalent resistance between the corners 1 and 6 as shown in Fig 5 126 use nodal method R ww www R 2 www R 8 R www www R R R R www R www R 3 Fig 5 126 5 R OB

Find the equivalent resistance between A and B in the following circuit 10 22 A www 52 592 1092 592 10922 ww 50 B 10 22

47 If each resistance in the fig is of 9 22 then reading of the ammeter is H 9 VT wwwwww Fwww www www www wwwww wwwww 121 2 A wwwww 4 9 A

14 An electrical network is formed by two hexagon and joining grid points with wires The resistance of each side and the connecting wires is R An ideal battery of emfE is joined as shown in figure Find the current passing through the battery Consider the wire connected with the cell is ideal take E 11 Volt R ohm 6 5 03

The given infinite grid consists of hexagonal cells of six resistors each of resistance R Then R R 1 1 2 2R 2 3 4R 3 3R 4

44 45 Resistors R and R have an equivalent resistance of 6 ohms when connected in the circuit shown below The resistance of R could be in 2 1 1 E www R R 2 5 4 4 Value of current i in the following circuit is 3 8

comes out at The current enters at A D Some of the resistances are shown What should be resistance of wrie CB so that it draws double of the current that enters the wire BF D 1 R 5 10 7 E R 5 R R 5 C R 5 A 2 F 3 R 5 2R 5 R B

While connecting 6 cells in a battery in series in 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 D01A 2102A 310 34 41043

Each of the resistors shown if fig has resistance R Find the equivalent resistance between A and B www b www e 1 a ww 7R 4 d A B W 2 5R 4 80 C 3 9R 4 h 4 11R 4

18 carries a current i is 1 2 Hoi 2R Moi 2TR 24 3 Moi 4 1 2 4TR H i T ion at the point O if the wir 4 y R X

In the circuit shown the equivalent resistance between A and B is AR 1 R 3 R 3 R R www R ming 34 R www 2 2R 5 4 2R R wwwo B

After how much time energy becomes e maximum value in a R L circuit where R 25 L 2mH 1 1 ms 2 0 5 ms 0 5 ms 3 2 ms 4 1

A potential difference of 2V is applied between the opposite faces of a Ge crystal plate of area 1 cm and thickness 0 5 mm If the concentration of electrons in Ge is 2 1019 m and mobilities of electrons respectively then the current flowing through the and holes are 0 36 plate will be A 0 25 A m volt sec and 0 14 B 0 45 A m volt sec C 0 56 A D 0 64 A

A network of resistors is connected to a 16 V battery with internal resistance of 192 as shown in Fig a Compute the equivalent resistance of the network b Obtain the current in each resistor c Obtain the voltage drops VAB VBC and VCD A 40 40 2 16 V J B 192 122 120 CAM D 60

oh 4 An electric current of 16 A exists in a metal wire of cross section 10 m and length Im Assumin free electron per atom the drift speed of the free electrons in the wire will be Density of metal 5 x 10 kg m atomic weight 60 A 5 x 10 m s C 4 x 10 m s According to Avogadro s hypothesis N N m M So n N m N VM M Hence total number of atoms n V NA Hence drift velocity v I neA 6 10 5 10 60 10 B 2 x 10 m s D 7 5 x 10 m s p density 5 x 1028 m 16 5x1028x1 6x10 19 10 IA LO 2 x 10 m s

The potential difference applied to an X ray tube is 5 kV and the current through it is 3 2 mA Then the number of electrons striking the target per second is 1 2 x 1016 2 5 x 1016 3 1 x 1017 4 4 x 1015

or the circuit shown in figure calculate a The current in the 2 2 resistor and p The potential difference between points a and b Solve using Superposition method 12 V 42 B 292 www 60 b

In the given circuit current flowing through 2 92 resistance is 10 VT 1 5 A 2 2 5 A 3 Zero 192 292 392 www 69

A flat coil of 500 turns each of area 50 cm rotates in a uniform magnetic field of 0 14 Wb m about an axis normal to the field at an angular speed of 150 rad s The coil has a resistance of 5 2 The induced e m f is applied to an external resistance of 10 S2 The peak current through the resistance is 1 1 5 A 2 2 5 A 3 3 5 A 4 4 5 A

13 An electric dipole is formed by two equal and opposite charges q with separation d The charges the same mass m It is kept in a uniform electric field E If it slightly rotated from its equilibrium orientation then its angular frequency o is a c gE 2md qE Vmd b 2qE V md d 2 qE md

D each of them decreases A wire of resistance R is bent into a square an equilateral triangle and a circle Effective resistance are determined across the diagonal of the square adjacent corners of the triangle and diameter of the circle The values are A R 2R R 49 4 B RRR C 4 9 2 non points A and B in the circuit R 2R R 2 9 4 D R R R R R 22 11 2 2

Four cells and six resistance are connected as shown in the figure Answer the following questions 1 2 A 30 9V 9V CO wwwwww 120 80 E 12V 602 Let potential at points B and D be VB and VD respectively Then VB VD is A 4V B 4V C 20 V my 20 1 www 1802 D The magnitude of current through 8W resistor connected between points B and E is A 0 25 A B 0 5 A C I A D 2 A

22 2 ent a c r 3 b 3r Jamni be d 2 3r 158 Calculate the equivalent resistance between A and B 3Q 39 www A 322 www www 3Q www 322 3Q 222 atfoy to offer srin www 32 322 a 9 2 b 3Q c 622 d 5 3 2 159 Find the equivalent resistance across AB A A 252 B BW T 081 292 TISTORE son intel1 781 252 parallel The net res a 222 b 3 165 In the circuit sho unknown resistor A circuit between poi 39 P WWW a 32 b 166 In the net work show A and B is A 2 S

A storage battery is connected to a charger for charging with a voltage of 12 5 Volts The internal resistance of the storage battery is 1 2 When the charging current is 0 5 A the emf of the storage battery is A 13 Volts C 12 Volts B 12 5 Volts D 11 5 Volts

nd the equivalent resistance between A and B in he following circuit A 22 ww ww 492 892 692 ww 10 22 B

In the circuit shown in the given figure the resistances R and R are respectively R ww 69 V a 14 92 and 40 2 c 40 2 and 30 0 5 AY R2 10 22 M 20 S2 1 A b 40 2 and 14 22 d 14 2 and 30 Q

2 An electric heater is rated 1 5 kW 220 V a Find the safe current which can flow through it b Can fuse of current rating 5 A be used with it c What must be the current rating of the fuse

The network shown in figure is part of a complete circuit If at a certain instant the current I is 5A and is decreasing at a rate of 103 A s then VB VA is I A B 1 5 V 3 15 V 1592 15 V 5 mH 2 10 V 4 20 V

9 A B and C are voltmeters of resistance R 1 5 R and 3R respectively as shown in the figure When some potential difference is applied between X and Y the voltmeter readings are VA VB and V respectively Then X A 1 VA VB Vc 3 V V V B Y 2 VA VB VC 4 V I

When two cells of emfs and 2 are connected in series so as to assist each other their balancing length on a potentiometer is found to be 2 7 m When the cells are connected in series so as to oppose each other the balancing length is found to be 0 3 m Compare the emfs of the two cells

14 Twelve equal resistors each R S2 are connected to form the edges of a cube Find the equivalent resis tance of the network A B ww D D C ww ww www B A a when current enters at A and leaves at A b when current enters at A and leaves at B tors at and leaves at B

Whenever each element of the circuit is multiplied by a factor say k then the equivalent resistance is also multiplied by the same factor

A potentiometer circuit has been set up for finding the internal resistance of a given cell The main battery used across the potentiometer wire has an emf of 2 0 V and a negligible internal resistance The potentiometer wire itself is 4 m long When the resistance R connected across the given cell has values of i infinity ii 9 5 92 the balancing lengths on the potentiometer wire are found to be 3 m and 2 85 m respectively to be m The value of internal resistance of the cell is CBSE AIPMT 2014 a 0 25 c 0 5 2 b 0 95 2 d 0 75