Current Electricity Questions and Answers

2 Two resistors R 500 of resistances R 300 3 2 and 4 2 are connected in series The equivalent resistance of the series combination is a 800 1 2 b 800 7 52 c 200 7 92 d 200 1 2

44 A battery of emi Eo long uniform wire having resistance 4 92 m The cells resistance 2 Q2 and 6 2 respectively are connected as of small emfs E 2 V and E 4 V having internal shown in the figure If galvanometer shows no deflection at the point N the distance of point from the point A is equal to Eo R 892 a 2 5 m c 125 m Hww E 4www E2 12 G N b 3 m a 4m B

For a black body at temperature 727 C its radiating power is 60 watt and temperature of surrounding is 227 C If temperature of black body is changed to 1227 C then its radiating power will be 1 304 W 3 240 W 2 320 W 4 120 W

sed in an experiment 46 The diagram to determine the emf and internal resistance of the cell C A graph was plotted of the potential difference V between the terminals of the cell against the current I which was varied by adjusting the rheostat What is the internal resistance of the cell a x y mtm b y V X V A c x y d y x

given in 42 In the circuit shown the resistances are ohms and the battery is assumed ideal with emf equal to 3 0 volts The resistor that dissipates the maximum power is a R c R3 3V 5092 R R www R36092 R4 3092 509 b R2 d R4 4

c R3 between any two resistance 3 In the diagram resistance across junctions is R R Equivalent terminals A and B is assume P and Q also as a junction a 11R 7 P A A B 18R b 11 Q 7R c 11 d 11R 19

A 1 F capacitor is connected in the circuit shown below The emf of the cell is 2 volts and internal resistance is 0 5 ohm The resistors R and R have values 4 ohm and 1 ohm respectively The charge on the capacitor must be fu tufa gai cont de a fa al 2 akce 30 via di fi luF D HH R www E 2V r 0 522 R www A 2 C B 1 C C 1 33 C D zero Your Answer 7

In circuit a the instruments read U 100V I 5uA In circuit b we have U 25 mV I 2 5 A What is the internal resistance of the cell in Ohm Round off to nearest integer Consider both instruments to be regular laboratory instruments If approximate integer value is x then fill the value of x 8 in your OMR sheet V 102

444 RA R3 R5 R R Consider the following electric circuit i Which two resistors are connected in seri es ii Which two resistors are connected in par allel iii If every resistor of the circuit is of 2 Q w hat current will flow in the circuit

A millivoltmeter of 25 millivolt range is to be converted into an ammeter of 25 ampere range The value in ohm of necessary shunt will be 1 1 3 0 001 AIPMT Prelims 2012 2 0 05 4 0 01

5 In the primary circuit of a potentiometer a cell of E M F 1 V and a rheostat of 1502 are connected in series If the resistance of the potentiometer wire is 1002 the minimum voltage at the ends of the wire in V will be 1 0 1 2 0 4 3 0 06 4 1 0

There are two concentric metallic spherical shells of radii a and b such that a b An ideal cell of emf is connected across the two shells The medium between the shells is filled with a dielectric of dielectric constant K and resistivity p For a point P at a distance from the common centre C where a r b A current density is B electric field is 2 ab pr b a ab r b a C current density is ab pr b a DI net current supplied by the cell is 4 ab

A finite chain of resistors is shown in the figure All the resistors in the chain are of the same value A current of 1 4 flows through the last resistor The current supplied by the battery is found to be n Find the value of n n 2 E wm R ww wm R www M mmm www R R R www R www R 14

A battery of emf 5V and internal resistance 52 is connected across a long uniform wire AB of length 1 m and resistance per unit length 5 502 m Two cells of 1V and 2V are connected as shown in the figure SV SQ W www 1Q 4 2V 202 P B A The null point is at A B If the Jockey is touched to point B the current in the galvanometer will be going towards B C When Jockey is connected to point A no current is flowing through 1 V battery D The null point is at distance of 8 15 m from A

In the voltmeters and the ammeters will be 10 Q V 10 V Circuit 1 102 102 www H 10 V V 2 Circuit 2 1 V V and i 1 2 V V and i 1 3 V V and i i 1 A A NEET 2019

Two 1 transformers are rated as 10 kVA 400 200 V and 5 kVA 400 200 V respectively The resistance and reactance are 0 04 j0 05 and 0 05 j0 04 respectively Is it possible to connect these two transformers in parallel when common load of 9th and 12th digits of your enrolment number kW with pf of 0 8 lagging Justify your answer Also find how much load the individual transformer can share Write your observations

Two coils P and Q are connected in series in one gap of a slide wire bridge and the null point is obtained at midpoint of the wire by putting a resistance of 37 5 2 in the other gap The two coils are then connected in parallel and null point is obtained at the midpoint of the wire by keeping 9 Q in the other gap The resistances of P and Q are A 20 Q and 17 5 9 30 22 and 7 5 Q 22 5 Q and 15 Q 22 Q and 15 5 Q C B D Pvt

A rk of eight resistors numbered 1 to 8 each equal to 292 connected to I a 3V battery of negligible internal resistance The current I in the circuit is 3V 1 ww 3 N E 2 B 1 0 25 A 3 0 75 A 4 ww 8 S C 6 F 2 0 5 A 4 10 A 7 D

12 13 14 For question numbers 11 12 13 and 14 two statements are given one labelled Assertion A and the other labelled Reason R Select the correct answer to these questions from the codes a b c and d as given below a Both A and R are true and R is the correct explanation of A b Both A and R are true but R is NOT the correct explanation of A c A is true but R is false d A is false and R is also false Assertion A To convert a galvanometer in to ammeter a small resistance shunt is connected in parallel to the coil of galvanometer Reason R An ideal ammeter has infinite resistance Assertion A The wire of potentiometer is made by constantan and manganin Reason R Constantan and manganin are alloys and dependence of resistivity of alloys in temperature is negligible Assertion A A particle will follow helical path in magnetic field if its velocity v and direction of magnetic field B are at angle of Reason R The component vsin o will provide the centripetal force and magnetic field will not apply any force on the component vcos p Assertion A In a metallic wire if we increase the temperature of wire the resistance of the wire also increases Reason R on increasing the temperature thermal velocity of electrons decreases and dingropoor in this way number of collision decreases 1 1 1

An electric circuit consists of a battery emf E 110V with internal resistance 50 and two resistors connected in parallel to the source as shown in figure Determine the value of R so of R so that get maximum power dissipated in resistance R ww www 50 2 E 110 V www r 50Q

The resistance thermometer of the wire in the platinum resistance at ice point is 5 22 and at steam point is 5 25 2 When the thermometer is inserted in an unknown hot bath its resistance is found to be 5 5 2 The temperature of the hot bath is a 100 C b 200 C c 300 C d 350 C

26 For the circuit shown below calculate a the value of resistor Rx such that the total power dissipated in the circuit is 2 5 kW and b the current flowing in each of the four resistors R 150 R 1002 250 V R 380 R

21 Effective resistance between point A and B for following network is each branch of resistance is 1N www Answer 1 www 0 0000 www A Accepted error B Explanation www

4 The network PORS shown in the circuit diagram has the batteries of 4 V and 5 V and negligible internal resistance A milliammeter of 20 0 resistance is connected between P and R Calculate the reading in the milliammeter Comptt All India 2012 20001 ww mA 2017 R www 6012

V www www R 16 A resistor of resistance R is connected in a circuit to two identical batteries The circuit also contains switch S and ideal voltmeter V as shown in the figure above The batteries both have an emf and internal resistance r The reading of the voltmeter is noted with the switch in the open position Which of the following best represents how the voltmeter reading after the switch is closed compares to the reading before the switch is closed A The reading of the voltmeter is the same B The reading of the voltmeter is higher C The reading of the voltmeter is lower D Cannot be determined without knowing the internal resistance of the batteries E Cannot be determined without knowing the emf of the batteries

PASSAGE I Two cells of 2 V each are connected in parallel An external resistance of 0 5 22 is connected in series to the junction of two parallel resistors of 6 22 and 2 22 and then to the common terminal of the battery through each resistor as shown in figure 1 0 5 92 2 V a 1 5 Q c 2 5 9 2 V 62 www 22 The total resistance of the circuit is b 2 0 22 d 3 0 Q 2 The potential difference across the 0 522 resistor is a 3 5 V b 2 5 V c 1 5 V d 0 5 V 3 The current flowing through 6 2 resistor is a 0 50 A b 0 25 A d 0 10 A

A constant voltage is applied across a wire of constant length How does the drift velocity of electrons depe on the area of cross section of wire

A wire of length 100 cm carries a steady current i The potentials at the ends of the wire is 4 V and 20 V The value of potential at x 20 cm is 20 V 100 cm 4 V 0 cmx x 20 1 0 8 V 2 O8Y cm 2 0 4 V 4 04 V

Consider the meter bridge circuit without neglecting end corrections If we used 10002 and 2009 resistance in place of R and S respectively we get null deflection at 33 0 cm If w interchange the resistances the null deflection was found to be at 67 0 cm If a and ar the end correction then the value of a should be R S 100cm B

There are m resistor each of resistance R First they all are connected in series and equivalent resistance is X Now they are connected in parallel and equivalent resistance is Y What is the ratio of X and Y

A R 5 B R 4 C R 2 2R www D R E 2R 21 R 23 Three resistors are connected to an ideal battery as shown in the figure above The battery has an emf E Two of the resistors have known resistances R and 2R The third resistor has unknown resistance X The current in two of the branches is shown What is the value of the unknown resistance X X

The figure shows 3n cells connected in series to form a circuit r is the internal resistance of each ce and e is the emf of each cell If polarity of n cell are reversed find the terminal voltage across A 2n cells n cells 6 3 3e 2 Zero 2e

10 Calculate the area of cross section of a wire of length 2m its resistance is 250 and the resistivity of material of wire is 1 84 10 6 Qm 11 Calculate the energy consumed by 120W toaster in 20 minutes

In the circuit shown R R 102 and resistance per unit length of wire PQ 1 cm and length PQ 10 cm If R is made 20 02 then to get zero deflection in galvanometer S is midpoint of wire PQ A The jockey at P can be moved towards right 2 cm B The jockey at Q can be moved towards left 2cm C The jockey at S can be moved towards left a distance 5 3 m D The jockey at all position fixed and R should be made 2012 12V vefata ufum R R 100 PQwi wf det PQR 120 2femeter A P2 cm B Q f 2 cm i s 5 3 1 102 cm met 10 cm 815 m fra feny

Two bulbs of power 30 W and 60 W are connected in series what will be ratio of potential drop across bulb 1 1 2 2 2 1 3 3 2 4 2 3 A current I flows along the length of an infinitely long straight solid pipe The current is uniformly distributed on the cross section Then incorrect statement 27 28 30 w 360 W gg at acara arm 1 1 2 Uch SIRTI 2 2 1 530d r EN Cara

55 Five equal resistances each of value R are connected to form a network as shown in figure The equivalent resistance of the network between the points A and B is B a c 1 5 8 R R SH 2 86 b 2R FALLER 8 d R R A R wwwww wwwwww R R C

Five equal resistances each of value R are connected in a form shown alongside The equivalent resistance of the network 8 1 Question Type Single Correct Type 2 3 Between the points B and D is R R Between the points B and D is 2 R Between the points A and C is 2R 32

16 Four ammeters with identical internal resistance r and a resistor R are connected to a current source as given If reading of A and A2 is 3A and 5A respectively then the reading A4 is a b C 1A 3A 5A 7A A2 A3 R www r

4 The current density varies with radial distance r as J ar in a cylindrical wire of radius R The current passing through the wire between radial distance R 3 and R 2 is 65 na R 2592 65na R 2938 a c b d 25 na R 72 81na R 144

The equivalent resistance between the terminal points A and B in the network shown in figure is R R 1 R R 7R 5 R R ww Question Type Single Correct Type R ww R R R R B

2 From P W t I Q t W QV show that P IV Three resistors with ratings of 3 ohms 5 ohms and 6 ohms are connected in series to a 12 volt source Draw the schematic diagram and the table and show all computations to fill up the table 10 marks 3 In problem 2 suppose you connect the three resistors in parallel Draw the schematic diagram and the table and show all computations to fill up the table 10 marks wwwwwwwwwwwwww

FIX Pre Medical Physics 4 Primary winding and secondary winding of a transformer has 100 and 300 turns respectively If its input power is 60 W then output power of the transformer will be 1 240 W 360 W 2 180 W 4 20 W The ratio of the secondary to the primary turns ower is

Q1 Determine the resistance of a metal tube in terms of the external diameter D the internal diameter d the length and the resistivity p Calculate the resistance of a copper tube 0 5 cm thick and 2m long The external diameter is 10 cm

2 A galvanometer has a resistance of 3663 ohm shunt S is connected across it such that 1 34 o the total current passes through the galvanomete Then the value of shunt is 1 3663 2 1112 3 107 70 OF

Two coils A of 12500 turns and B of 16000 turns lie in parallel planes so that 60 of flux produced in A links coil B It is found that a current of 5 ampere in A produces a flux of 0 6 mWb while the same current in B produces 0 8 mWb Determine 1 mutual inductance 2 coupling coefficient 5

The voltage of clouds is 4 x 106 V with respect to ground In a lightning strike lasting 100 ms a charge of 4 C is delivered to the ground The average power of lightning strike is assume complete discharges

In the figure shown each resistor is of 20 ohms and the cell has emf 10 volt with negligible internal resistance Then rate of joule heating in the circuit is in watts E O O 10000 11 O 100 11 11 wwwww www www r www

10 000 alpha particles pass per minute through a straight tube of radius r What is the resulting electric current The potential difference applied to an X ray tube is 5 kV and the current through it is 3 mA What is the

1 Alternating current cannot be measured by d c meter because a a c cannot pass through a c ammeter b a c changes direction c average value of current of complete cycle is zer d a c ammeter will get damaged AIEEE 2004 AIIMS 20

Progress Two resistors 47 2 and 49 30 are connected in parallel The current through the 49 3 Q resistor is 4 06A a Determine the current in the other resistor b What is the total power supplied to the two resistors a Number i Units V