Current Electricity Questions and Answers

n Find the resistance across AB From figure it is clear that terminal A and point 2 are common point and terminal B and po are common point so redrawing the diagram we have 60 A Rp 2 5 3 2 10 22 www 1592 Now 62 102 and 15 are in parallel so effective resistance is 1 1 6 10 15 B

45 A stream of electrons is projected horizontally to the right A straight conductor carrying current is supported parallel to the electron stream and above it If the current in the conductor is from left to right then what will be the effect on the electron stream only due to magnetic effect A The electron stream will be speeded towards the right B The electron stream will be retarded C The electron stream will be pulled upwards D The electron stream will be pulled downwards

100H C 1 F R 10k When all the switches are open V2 reads 100V All the voltmeters are hot wire voltmeter which read r m s value of voltage Initially S1 S2 and S3 are open In the figure frequency of the A C source is 50 THz with L S S R wwwwww S3 At certain instant of time voltage across R is increasing magnitude of potential difference across inductor and capacitor simultaneously increases or decreases Readings of all other voltmeters are also equal to 100V When S and S2 are both closed reading of V4 remains 100v When only S closed reading of V4 decreases

13 If two bulbs of power 60 W and 100 W respectively each rated 110 V are conhe of 220 V then 1 60 W bulb will fuse 3 Both bulbs will fuse 2 100 W bulb will fuse 4 Bulbs will not fuse

1 MQ 2 An electric cable contains a single copper wire of radius 9 mm It s resistance is 5 Oh This cable is replaced by six insulated copper wires each of radius 3 mm Find t resultant resistance of cable 3

Q5 In the resistor network shown in Fig below all resistor values are 29 A current of 1A passes from terminal a to terminal b as shown in the figure Calculate the voltage between terminals a and b a 1A www ww www ww www ww www 1A R 252

A galvanometer has a resistance of 20 0 ohm What is the value of shunt resist ance required so that only 1 of the total current pas ses through the galvanometer Also cal culate the effective resistance of the combinatio n

3 Two very long wires carrying a current I of 2 0 A out of the page are at two of the corners of an equilateral triangle as shown in Fig 6 below The sides of the triangle are 1 0 m long Find the direction and magnitude of the magnetic field at P the third corner of the triangle 11 P Fig 6 1 0m

There are three bulbs B B2 and B3 rated as 100 W 60 W and 60 W respectively These can be operated upto 200 V Increasing order of their brightness for given arrangement is B B B 100 V B3 B2 B B B B3 B B B3 B B3 B

2 00 nF capacitor with an initial charge of 4 97 C is discharged through a 2 36 kn resistor a Calculate the current in the resistor 9 00 us after the resistor is connected across the terminals of the capacitor Let the positive direction of the current be define such that d mA d b What charge remains on the capacitor after 8 00 us HC c What is the magnitude of the maximum current in the resistor

A particle of mass m and charge q is fastened to one end of a string fixed at point O The whole system lies a frictionless horizontal plane Initially the mass is at rest at A A uniform electric field in the direction shown then switched on Then A E 60

When an external resistance is connected to a battery of emf 80 V an ammeter records 200 mA If a voltmeter is connected to the two ends of the external resistance it records 60 V Determine the rate of supply of energy from the battery and also the rate of consumption of energy by the resistance 16 W 12W

13 A hollow cylindrical conductor of length 1 m has inner and outer radii 1 mm and 2 mm respectively If resistivity of the material is 2 x 10 8 22 m then resistance in between the terminals A B as shown below is 2 mm 1 mm 1 1 2 x 10 30 3 2 1 x 10 62 A K COB On or fc 501360 station ry ston 1 m 2 1 2 x 10 6 blest 4 2 1 x 10 6

14 The following figure shows a part of a circuit the potential difference between C and B Vc Ve is 12 5A D 22 12 V C www 1 10 V 2 13 V 3 20 V 32 3 V E 42 2A Www B 62 6 A

68 In producing chlorine by electrolysis 100 power at 125 V is being consumed How much chlorine per minute is liberated E C E of chlorine is 0 367 x 10 6 kg a 1 76 10 kg c 17 61 x 100 kg b 9 67 10 kg 3 d 3 67 x 10 kg

A cell of e m f 2 V and negligible internal resistance is connected in series with a potentiometer wire of length 100 cm The e m f of the Leclanche cell is found to balance on 75 cm of the potentiometer wire The e m f of the cell is A 3 5 V e 1 5 V B 2 5 V D 0 5 V

d 2 3 4 69 For what value of R in the circuit as shown in figure current passing throu zero B www 202 9 V a 10 30 ww LL F 402 6 V 3 V R E resistance will be YSICSKOTA

th a a 6 V c 3 V c 3 4 NEET 16 I 73 The potential different VA VB between the points A and B in the given figure is VA O A b 5 4 d 3 2 I 2A 222 3 V wwwwww b 9V d 3V 192 VB B is NEET 16 II

A potentiometer having a wire of length 10 m and resistance 20 Q is connected to an accumulator of e m f E through a resistance box When the resistance in the box is 20 a null point is observed at 5 m for a cell of e m f E The ratio of E to E is A 1 4 C 3 1 B LD 2 1 4 1

In the shown arrangement of the experiment of the metrebridge if AC corresponding to null deflection of galvanometer is x what would be its value if the radius of the wire AB is doubled A X THE B x 4 R C 4x D 2x R

A wire of length 100 cm is connected to a cell of e m f 2 V and negligible internal resistance The resistance of the wire is 3 The additional resistance required to produce a potential drop of 1 millivolt per cm is A 60 Q2 5792 B 47 92 D 35 Q

Potentiometer wire of length 1 m is connected in series with 490 resistance and 2 V battery If 0 2 mV cm is the potential gradient then resistance of the potentiometer wire is 7 9 2 6 9 Q A 4 992 C 5 99 B D

A battery of e m f 2 V and internal resistance 22 is connected to an external resistance 8 2 If the length of the conductor is 4 m then potential gradient between the two ends of the wire is A 0 4 V m C 4 V m B D 8 V m 2 V m

The resistance per unit length of a wire is 1 22 m A Leclanche cell of e m f 1 45 V is balanced against 2 9 m length of potentiometer wire The current through the wire is 1 A B 2 A A C 0 5 A D 0 1 A

A resistance of 990 2 and a cell of emf 2 V is connected in series with a potentiometer wire having a length 2 m and resistance 10 2 The potential gradient along the wire will be A 0 01 V m B 0 02 V m C 0 03 V m D 0 04 V m

In a metrebridge experiment null point is obtained at 20 cm from one end of the wire when resistance X is balanced against another resistance Y If X Y then where will be the new position of the null point from the same end if one decides to balance a resistance of 4X against Y A 50 cm C 40 cm B D 80 cm 70 cm

9 For the circuit shown in the figure the current through the inductor is 0 9 A while the current through the condenser is 0 4 A Hence current drawn from the generator is 1 1 3 A 3 0 6 A mom voooo EN 2 0 9 A 4 0 5 A

Two resistances are connected in the two gaps of a metrebridge The balance point is 20 cm from the zero end When a resistance of 15 Q2 is connected in series with a smaller of the two resistances the null point shifts to 40 cm The smaller of the two resistance has the value 992 12 Q2 A 892 C 102 LOY D

With resistances P and Q in the left and right gaps of a metrebridge the balance point divides the wire in the ratio 1 3 When P and Q are increased by 40 2 the balance point divides the wire in the ratio 3 5 The values of P and Q will be respectively A 302 102 B LECT D 10 30 20 52 60 52 60 2 40 2

Alternating Current In a step up transformer the Leclanche cell Emf 1 5 Volt is connected across primary The voltage developed in secondary would be

A uniform wire of 16 Q2 is made into the form of a square Two opposite corners of the square are connected by a wire of resistance 16 2 The effective resistance between the other two opposite corners is 852 10 452 A 32 2 B 20 C 82

metrebridge the gaps are closed by two resistances P and Q and the balance point is obtained at 40 cm When Q is shunted by a resistance of 10 2 the balance point shifts to 50 cm The values of P and Q are Q P 40 cm 4 10 3 52 592 B 20 9 30 0 HH

4 The phase difference between source emf and curent is 0 A power transmission line feeds input power at 2300V to a step down transformer with its primary windings having 4000 turns What should be the number of turns in the secondary winding in order to get output power at 230V 1 300 2 250 4 450 3 400

In the circuit shown the current drawn from the battery is 4 A If 10 2 resistor is replaced by 20 2 resistor the current drawn from the circuit will be A 1A B C D 1 5 A 3 A 3 4 A 12 mm 792 www www 30 1092 2122 www 12V 12 V

In a metrebridge when R and X are the resistances in left gap and right gap respectively the null point is obtained at 40 cm from the left Now when the resistance R is in left gap and X in right gap then the null point is obtained at 60 cm from the left When the resistance in left gap is changed to R R the null point will be at A B C D 25 6 cm from left 68 4 cm from left 31 6 cm from left 74 4 cm from left

5 A conductor of area of cross section A having charge carriers each having a charge q is subjected to a potential V The number density of charge carriers in the conductor is n and the charge carriers along with their random motion are moving with average velocity v A current I flows in the conductor If j is the current density then I rated a 1 n qV in the direction of charge flow 2 nqV in the direction opposite to charge flow 3 nqV in the direction perpendicular to charge flow 4 nqv in the direction of charge flow 1 3 lg an ferm 3 nqV A ale va ich n 2 ech 4 Vg faurita que fa VaR

12 A homogeneous glass cone of half angle 30 is placed inverted on a disc so that its axis is vertical Radius of the disc is 4 0 cm and the tip of the cone coincides with the centre of the disc What is the radius of the disc visible through the circular base of the cone from a large height Refractive index of the glass of the cone is 1 5

99 In the below circuit the battery E has an emf of 12 V and zero internal resistance While the battery E2 has an emf of 2 V 2 N E 500 Q www 612 XQ G E b 100 d 200 2V If the galvanometer G reads zero then the value of the resistance X in ohms is a 250 lo 50 v iR

105 In the given circuit the voltmeter records 5 V The resistance of the voltmeter in is V 1 VO VB 100 1 a 200 c 10 100 Q wwwww 10 V 50 2 wwwww b 100 d 50 001

e 33 It takes 16 min to boil some water in an electric kettle Due to some defect it becomes necessary to remove 10 turns of heating coil of the kettle After N 2 repairs how much time will it take to boil the same mass of water a 17 7 min b 14 4 min c 20 9 min d 13 9 min 14 4 on between points A and B is

118 B B and B3 are the three identical bulbs connected to a battery of steady emf with key K closed What happens to the brightness of the bulbs B and B when the key is opened B KO B B3 16 a Brightness of the bulb B increases and that of B decreases b Brightness of the bulbs B and B increases c Brightness of the bulb B decreases and B increases 1 bulba B and B decreases

Problem 4 In the figure below given two ideal generators and three resistors 1 12V 82 5V R 40 R 20 and R3 30 est fire R R3 un R E2

Four identical resistors each of resistance 2 Q are connected to battery of 20 V and internal resistance 2 92 as given below The reading of ideal ammeter A and A are 20 V 292 1 8 A 8 A 29 3 10 A 10 A www 292 www 22 222 www A 2 5 A 5 A 4 4 A 4 A A

19 Three charges 4q Q and q are placed in a straight line of length 1 at points at distance 0 1 2 and I respectively What should be Q in order to make the net force on q to be zero c 1 2 2 9 a 9 b 2q d 4q 90 An electron falls from the

Two parallel conductors each of 0 50 m length separated by 5 0x10 m and carrying 3 0 A in opposite directions will experience what type and magnitude of mutual force Ho 4x107T m A a Attractive 0 06x10 N b Repulsive 0 60x10 N c Attractive 1 8x10 N d Repulsive 1 8x10 N

91 In the circuit given here the points A B and Care 70 V zero 10 V respectively Then 20 W AWWWWW 10 W D B www 1905 30 www C a the point D will be at a potential of 60 V b the point D will be at a potential of 20 V c currents in the paths AD DB and DC are in the ratio of 1 2 3 d currents in the paths AB DB and DC are in the ratio o 3 2 1

A hemispherical surface of radius R is placed with its cross section perpendicular to a uniform electric field as shown in figure The electric flux through the surface is ogtado olgnies of sub ac sig a R E b 2 R E c 4 R E d zero d 1 R

The emf E and the internal resistance r of the battery shown in figure are 4 3V and 1 002 respectively The external resistan ce R is 500 The resistance of the ammeter and voltameter are 2 002 an d 2000 respectively Find the respective reading of the voltmeter E ww R www A

The current i drawn from the 5 volt source will be 1 2 3 4 0 5 A 0 67A 0 17 A 0 33A Correct Answer 1 Status unattempted 2 502 1092 ww 1002 www 1092 ww 5 volt 2092 ww

The magnitude and direction of the current in the circuit shown will be 192 a d 3 e www 10 V 32 ww 7 A from a to b through e 3 4 V A 7 B A from b to a through e C 1 A from b to a through e 1 A from a to b through e 202 ww b ww C