Current Electricity Questions and Answers

Two bulbs B B each having resistance 50 2 are connected according to the figure Which bulb will glow with more brightness B 1 B 3 Both equally R 5092 X 500 5092 5092 E B 2 B 4 Data is not complete

in the circuit shown which of the following statement for CORRECT 3 0 2 2 4 V 10042 sin 377 R 1000 X 1000 www ART Power factor of the rout Reactance of the circuit is equal to resistance of the circuit Cincuit is not in a state of rosononco Average power dissipated in the circuit is 100 W X 500 Vior 1000099

Two resistors have resistances R smaller and R larger where R smaller R larger When the resistors are connected in series to a 12 0 V battery the current from the battery is 1 76 A When the resistors are connected in parallel to the battery the total current from the battery is 9 78 A Determine the two resistances R smaller i DU 6 82 1 23 Units 22 Units Q

A solar cell generates a potential difference of 0 1V when a 250 Q is connected across it and a potential difference of 0 3 V when a 1000 Q resistor is substituted The emf of the cell is O 3 0 volts O 0 6 volts O 6 0 volts O 0 3 volts O 0 9 volts

20 Which of the following statement is correct a Kinetic energy of a system can be changed without changing its momentum b Kinetic energy of a system cannot be changed without changing its momentum C Momentum of a system cannot be changed without changing its kinetic energy d Body cannot have energy without having

12V R 1002 M SR 200 R3 15022 B Ry 2502 R5 100 C R6 3002 a Find the current flowing through each resistor ie resistors R1 R6 2 Knowing that the length of each of the sides of this circuit are 3cm long what is the strength of the magnetic field at points A B and C Note only consider the contributions from the four edges of the loop surrounding each point consider the other ontributions to aligablo

Two identical point charges are kept at a distance d third point charge is placed on the perpendicular bisectc of the two charges at a distance x Show that the thir charge will experience maximum force when x d 2 2

A wire with a length of 150 m and a radius of 0 15 mm carries a current with a uniform current density of 2 8 x107 A m The current is Select one O a 5 9 A O b 300 A O c 26000 A O d 2 0 A O e 0 63 A

A certain capacitor in series with a resistor is being charge At the end of 10 ms its charge is half the final value The time constant for the process is about Select one O a 14 4 ms O b 2 3ms O c 6 9ms O d 10 ms O e 0 43 ms

A galvanometer of resistance 3 9952with a scale divided into 150 equal divisions has current sensitivity of 10 divisions per milli ampere Find shunt resistance for making an ammeter of range 0 6A A 1 25 x 10 2 B 12 5 x 10 02 C 125 x 10 2 D 10 x 10 30

circuit given in figure 1 and 2 are ammeters Just after key K is pressed to complete the circuit the reading will be 1 R www R mmmm wwww 3 1 Zero in 1 maximum in 2 2 Maximum in both 1 and 2 3 Zero in both 1 and 2 4 Maximum in 1 zero in 2

7 In the circuit shown in figure find i ii iii iv the current in the resistor R the value of resistance R the unknown emf If the circuit is broken at point x what is the current through the resistor R X 6 92 www 4A 392 6A

A 120 V power line is protected by a 15 A fuse What is the maximum number of 120 V 500 W light bulbs that can be operated at full brightness from this line Select one O a 5 O b 2 O c 1 O d 44 e 3

Figure shows a circuit containing three resistor X X X having resistance R each an inductor capacitor and an emf source having inductance L L capacitance C emf respectively Given R VC The switch is first connected to position 1 When charge on capacitor becomes half of it maximum possible value then switch S is connected to position 2 Current in resistance X just after shifting the switch from position 1 to position 2 is given L 5mH C 2 F R 100 5V L C R www up X3 R R www S X X

5 1 1 volt 3 3 volt X X A X OZZAZZ X X X X X The e m f induced between points A and B of the rod which is being rotated with constant angular velocity in uniform magnetic field is Point A is mid point of rod 2 rad s BR 1m B 1T 12 4 3 1 volt volt

4 A particle of mass m is projected upwards with V velocity v 2 where v is the escape velocity e e then at the maximum height the potential energy of the particle is R is the radius of earth and M is the mass of earth 1 3 GMm 2R 3GMm 4R 2 4 GMm 4R 2GMm 4R GUT G 3 fati 1 ht 3 11 30

a A capacitor has a capacitance of 30 F which is connected across a 230 V 50 Hz supply Find a capacitive reactance b rms value of current c power d power factor and e equations for voltage and current b Find I and Vab in the circuit 30 V 10 V 30 100 a 0 Vab 592 8 V

A frame made of a homogenious wire is shown in figure The number of successively embeded equilateral triangles with sides decreasing by half tends to infinity The side AB has resistance R The resistance RAB is A A Zero B Infinity C 2R 7 D 7 1 Ra B

3 A capacitor charges from a cell through a resistance the time constant is T In what time will the capacitor collect 10 of its final charge 1 Tlog 0 1 10 Tlog 2 Tlog 0 9 11 4 Tlog 10 discharges through

A current of 0 20 A passes through a 3 0 ohm resistor The resistor is connected in series with a 6 0 V battery and an unknown resistor a Draw a circuit diagram showing all the information above b Calculate the resistance of the unknown resistor

A 10 m long potentiometer wire is connected to a battery having a steady voltage and negligible resistance A leclanche cell is balanced at 4 m length of the wire If the length is kept the same but its cross section is doubled the null point will be obtained at A B C 8 m 4 m 2m None of these Correct Answer

59 Six resistors each of 10 are connected as shown The equivalent resistance between points X and Y is X Yo 1 20 S 2 5 W www 3 25 3 4 10 CYPHAENG MODULE ON LE IN

L 3 1 x 106 A 4 1 x 10 A 11 The current in a conductor varies with time t as 1 2t 3t A where I is amperes and t in seconds Electric charge flowing through a section of the conductor during t 2 s to t 3 s is 1 10 C 2 24 C AL C 3 33 C 4 44 C 10 000 electrons are passing per minute through a tube of radius 1cm The resulting current is 1 10000 A

Consider the following circuit and select the correct alterative s 402 www 2V www 602 A 652 402 www 40 www B A Current through each cell is A B Current through each 62 resistance is A 6 312 342 C Current through each 302 resistance is A 1 D Current through each 422 2V

Q4 Find the current flowing through each cell in the circuit shown in Fig Also calculate the potential difference across the terminals of each cell ir AQ 6 411 AT 10 V 10 2 4 V 13 V 252 192 1 1 PB 13

4 0 5 x 10 19 A There are 8 4 x 1022 free electrons per cm in copper The current in the wire is 0 21 A e 1 6 x 10 19 C Then the drifts velocity of electrons in a copper wire of 1 mm cross section will be nwone 192 1 2 12 x 10 5 m s 3 1 56 x 10 5 m s There is a current of 40 amporos 2 0 78 x 10 5 m s 4 none of these

107 In a closed circuit to maintain a steady current an external agency moves electrical charge from 1 Lower to higher potential energy 2 Higher to lower potential energy Lower to higher potential 4 Higher to lower potential 12P 200x300x4

An ammeter of resistance 0 80 2 can measure current upto 1 0 A i What must be the value of shunt resistance to enable the ammeter to measure current upto 5 0 A ii What is the combined resistance of the ammeter and the shunt

Q 101 Consider the double cube resistor network shown in Fig Each side of both cubes has resistance R and each of the wires joining the vertices of the two cubes also have same resistance R Find the equivalent resistance between points A B B

The four arms of a Wheatstone bridge have resistances as shown in the figure A galvanometer of 15 resistance is connected across BD Calculate the current through the galvanometer when a potential difference of 10 V is maintained across AC B 71000 6002 100 1 4 87 mA 2 2 44 mA 3 2 44 A 4 4 87 A www 50 10 V

Three 200 Q resistors are connected as shown in figure The maximum power that can be dissipated in any one of the resistor is 50 W Find the total power dissipated in the circuit for maximum safe voltage across the terminals A and B 1 2 Question Type Single Correct Type 3 www A 2000 75 W 150 W 2009 www 100 W www 20092 B

1 Phase impedance of a 3 phase 415V 60Hz star connected load is 120 Find the line current drawn by the load 2 Phase current of a 3 phase 415V 50Hz A connected load is 102 90 Find the phase impedance of the load

Fourteen identical resistors each of resistance R are connected as shown in the figure The equivalent resistance between the points A and B is G a R A D b 14R R R H c R R R 14 E R R B d 1 2R

55 Two conducting plates A and B are placed parallel to each other A is given a charge Q and B a charge Q The surface charge density at the inner surface of the plate A is S surface area of each face of plate 1 3 Q U 2S Q Q 25 2 4 2S Q 3 60 A TH po

e given circuit diagram switch was connected to position 1 for long time At t 0 switch is shifted from position 1 to position 2 Find the final charge on capacitor 2C C r V CV C 2 2C HH 2CV 4CV

2 Consider the following statements and select the correct statement s Current is the time rate of flow of charge through any cross section For a given conductor current does not change with change in cross sectional area I II III The net charge in a current carrying conductor is infinite a I and II b II and III c I and III d I II and III

Four identical cells each having emf E and internal resistance r are connected in series to form a loop ABCD as shown in figure Find potential difference across AB and AC E www www www E B E NAB I 2E 4r 24 2 E EXX 2x VAC 2E E 2 24 C x 2

As shown in the figure a cylindrical conductor has a length 2L It has inner and outer radius 1 and 12 Its Resistivity is p Determine the equivalent resistance of the conductor across the two lateral faces inner and outer A B C 12 r1 P 2 L P 4 L P 4 L P In In In In I 12 r1 12 2L 12

2 180 An increase in equivalent conductance of a weak electrolyte with dilution is mainly due to Increase in number of ions only Increase in ionic mobility of ions only 100 ionisation of electrolyte at normal dilution Increase in both number of ions and ionic mobility of ions

galvanometer and the deflection produced is 30 If three such cells are connected in series and the combination is connected to the same galvanometer the deflection will be then find n EXPLANATION I As I I 31 tan 0 tan 0 tan 30 tan 0 tan 0 3 0 5 n 3 KEY CONCEPTS Correct Answer 3

Which of the following graphs represents the correct variation of inductive reactance XL with frequency y of ac source O X LL

In the figure 107 V R 8 38 Q R 21 20 R3 35 7 0 and L 2 56 H Immediately after switch S is closed what are a i and b i2 Let currents in the indicated directions have positive values and currents in the opposite directions have negative values A long time later what are c i and d i2 The switch is then reopened Just then what are e i and f i2 A long time later what are g i and h i2 8 ww www R R L

A conductor with rectangular cross section has dimensions ax 2a x 4a as shown in figure Resistance across AB is x across C X Then the value of is fyis A ENGL B

till it reaches the centre of 5 12 A circuit element is placed in a closed box At time t 0 constant current generator supplying a current of 1A is connected across the box Potential difference across the box varies according to graph shown in figure 5 248 The element in the box is 2 V volts A Resistance of 20 C Inductance of 2H 3 Figure 5 248 B Battery of emf 6V D Capacitance of 3F A C

2 A steady current flows in a metallic conductor of non uniform cross section The quantit along the length of the conductor is are 1 current electric field and drift velocity 2 drift speed only 3 current and drift speed 4 current only 22 An immersion heater is rated 836 watt It should heat 1 litre of water from 10 C to 40 C in about 1 1 200 sec 2 150 sec 3 836 sec 4 418 sec 40 23 In the circuit shown in figure the heat produced in 552 resistance is 10 calories second The heat produced in 45 resistance is 452 552 652 2 2Cal s matem sunt enostale to bosga fimb bo oom T 3 3Cal s pictance is zero 30 4 4Cal s Rupee

An npn transistor operates as a common emitter amplifier with a power gain of 106 The input circuit resistance is 100 2 and the output load resistance is 10 kn The common emitter current gain B will be Round off to the Nearest Integer

14 Potential difference across AB i e VA VB is A 12 V 22 1 10 V 3 6 V www B 2 8 V 4 Zero 6 V 42

4 An electrical appliance of power 1 5 kW is used for 4 hour each day Find a the electrical energy consumed in kWh each day b The electrical energy consumed in 60 days c The cost of electrical energy consumed in 60 days at the rate of Rs 5J kWh 3M per

In the circuit shown here the transistor used has a current gain 100 What should RB be the base resistor RB so that VCE 5 V neglect VBE a 200 x 10 Q b 1 x 106 Q c 500 S d 2 x 10 2 www 1kQ CA E 10 V VCE HHHHH

2 In the following circuit diagram an infinite series of resistances is shown What is the equivalent resistance between points A and B B 10 12 202 202 www 20 to TERRA DE MIEL DE to o