Current Electricity Questions and Answers

Q10 In the potentiometer setup a driving cell with EMF 25V and interval resistance in is used Length of the potentiometer wire is 150cm and its resistance is 40 The balancing length for which galvanometer shows zero deflection is Driving cell Options 55cm 25cm X 45cm 40cm 192 25V IN 10 ww G B R 49 A

Two conductors of same length and area of cross section are connected in series as show in the figure An electric current i flows through them The total charge accumulated at junction would be p and 2p are their resistivity 3p H P 0

A pure inductor of 30 0 mH is connected to a source of 250 V Find the inductive reactance in and rms current in A in the circuit if the frequency of the source is 80Hz Options 1 3 4 8T 4 2 90 T 60 4 8T E 52 I 50

Eight resistors are connected in a circuit as shown below If Rxy represents equivalent resistance between any points x and y then A B 50 20 30 40 40 30 60 50 D a Resistance between AB CD b Resistance between AC BD c Resistance between AC BC d Resistance between AD BD

5 For the circuits shown in Fig 5 a and Fig 5 b determine the value of load resistance R so that it will receive maximum power Also calculate the value of maximum power E 12 V ww 202 202 ww ww 202 Fig 5 a ww 252 202 www www B 2 R ww 302 12V www 302 www R Fig 5 b 6 A

7 Find the static and dynamic resistance of a p n junction germanium diode if the temperature is 27 C and IO 1uA for an applied forward bias of 0 2V If the temperature increase to 40 C what will be the change in the diode current

which has 2 Columns Column I and Column II Column I has four entries A B C and D Column has four entries P Q R and S Match the entries in Column I with the entries in Column II Each entry in Column I may match with one or more entries in Column II Match the Columns A B C 0 Column l The rate at which electrical energy is dissipated in an electric circuit is called When resistances are connected in series When resistances Gre connected in parallel Product of square of current and Column Il Q Net resistance is more P than the largest individual resistance 1 Req R R Electric power R R3 Net resistance is less S than the smallest individual resistance

The value of Resistance R in 2 such that heat developed in it is maximum when switch S is open Then find the value of 10R In the circuit 10V 10 60 122 www www 120 60 www r 10 www

8 A battery of unknown emf is connected across resistances as shown in fig below The voltage drop across the 8 Q resistor is 20 V What will be the current reading in the ammeter What is the emf of the battery Ans 0 705 A 67 25 V 852 1152 1152 Fw 1352 1552

Find the resistance between terminals X and Y of the bridge circuit shown in Fig 6 applying a delta to star conversion and b star to delta conversion X B 402 10 3 ww 202 Fig 6 692 40 C

In the following figure two insulating sheets with thermal resistance R and 2R are shown The temperature of the interface 0 is 1 20 C 3 75 C 3R R 20 C 0 100 C 2 60 C 4 80 C

that of steel then Both have equal conductivity O b Copper is a good conductor than steel a O c Steel is a good conductor than copper What will be the specific heat of chromium when the temperature is raised from 12 C to 25 C after adding energy of 42 J to 0 2 Kg of chromium a b c d 20 J Kg K 16 J Kg K 12 J Kg K 10 5 J Kg K

PASSAGE A 230V de shunt motor takes 51 A current at full load Motor has armature resistance and field winding resistance of 0 1 ohm and 230 ohm respectively By using these parameters determine following Choose the correct options Marks 1 Analyze the shunt field current af dc motor OPTIONS 1A

The ratio of thermal conductivity of two rods of different material is 5 4 The two rods of same area of cross section and same thermal resistance will have the lengths in the ratio BHU 2000 BVP 2003 4 5 9 1 C

1 The diagram shown below depicts a situation where a potential difference of 220V is applied across two ends of rheostat The resistance of rheostat is 7000 2 For the situation a voltmeter having a resistance of 3000 2 is connected between the points X and Y If the point Y divides XZ in the ratio of 1 6 what will be the reading of the voltmeter 220 V V

In the given capacitance circuit all the capacitors are uncharged Find the charge flown through the battery as the switch S is clo 1 F 1 F 1 F 1 F 130 V 2 F 2 F Options 1 135 C 2 150 C 3 155 C 4 160 C S 0 5 F 0 5 F HH

A number of cells of negligible resistance are connected with two resistances in series A voltmeter of resistance 5000 while connected with these two resistances reads 4 V and 6 V respectively Find the magnitude of the resis WBJEE 2000 16670 25000 tances

88 A steady current flows in a metallic conductor c non uniform cross section The quantity quantitie that remain constant along the length of conduct is are 1 current electric field and drift speed 2 drift speed only 3 current and drift speed DAW 4 current only

Q 6 In an industry an engineer is designing a dc shunt machine working as a motor It is containing an armature resistance of 0 060 and shunt resistance of 2200 in dc shunt motor When he gives supply of 220V dc then motor runs at a speed of 1000rpm Initially dc shunt motor works at no load and motor is taking 6A current Now when he places a load so motor takes 31A current Then evaluate a Speed of motor at which motor is running at full load b Speed of motor at which motor is running at no load

Q 14 In any power plant it is having three phase 440V 50Hz ac supply and carrying some electrical equipments for working on a machine In a manager room there is a 6 pole induction motor and its slip is to found be 0 04 Then determine following a Rotor speed relative to the stator structure b Frequency of rotor currents at standstill

A 230V D C shunt motor has an armature resistance of 0 502 and Rsh of 1152 At no load the speed is 1200 r pm and the IA is 2 5A On application of rated load the speed drops to 1120 r p m determine the line current and power input when motor delivers the rated load

Q25 A person is working with an electrical circuit having a load resistance of 100 KQ and two digital multimeters of internal resistances 10 MQ and 1000 KN Which multimeter he should use for the measurement of voltage across the load resistance Give reason in support of your answer

Q3 Three 20 22 non inductive resistors are connected in star across a three phase supply the line voltage of which is 480 V Three other equal non inductive resistors are connected in delta across the same supply so as to take the same line current What are the resistance values of these other resistors and what is the current flowing through each of them

61 Power dissipated across the 8 2 resistor in the circuit shown here is 2 W The power dissipated in watt units across the 3 2 resistor is 1 2 19 wwww wwww 892 3Q www i AIPMT Prelims 2006 2 1

Q2 Each phase of a delta connected load comprises a resistor of 50 2 and capacitor of 50 F in series Calculate a the line and phase currents b the total power and c the kilovolt amperes when the load is connected to a 440 V 3 phase and 50 Hz supply

In producing chlorine by electrolysis 100 kW power at 125 V is being consumed How much chlorine per minute is liberated ECE of chlorine is 0 367 x 10 6 kg C AIPMT Prelims 2010 1 1 76 10 kg 3 17 61 x 10 kq 2 9 67 10 3 kg 4 367 x 10 3

20 The resistances in the two arms of the meter bridge are 59 and R2 respectively When the resistance R is shunted with an equal resistance the new balance point is at 1 6 1 The resistance R is AIPMT 20141

21 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 The value of internal resistance of the cell is AIPMT 2014 1 0 25 9 3 05 O 2 0 959 4 0 75 9

29 If voltage across a bulb rated 220 V 100 W drops by 2 5 of its rated value the percentage of the rated value by which the power would decrease is AIPMT Prelims 2012 1 5 2 10 3 20 1 2 5

2 Using the five band code indicate the colors of the bands for each of the following resistor 520 2 1 1 Point Green Red Brown Black Brown Green Red Black Black Brown Green Red Black Brown Black Green Red Brown Black Black

Two resistances R r and an inductor of inductance L are connected in series with an A C voltage source Three voltmeter are also connected as shown in the figure Reading of voltmeter V 56 V V 120 V V 160 V Then A Voltage across inductor is 96 volt B Voltage across resistance r is 72 volt C 3 D www R Power factor of circuit is 3 Power factor of inductor plus resistance r is mooooowww L r

In the figure c 8 51 V R 23200 R 32100 and Rg 3950 02 What are the potential differences in V a VA VB b VB Vc c Vc Vo and d VA VC a Number i b Number i c Number i Units Units Units

each of the circuits shown below each have the same resistance Which of the following gives the circuits in order of increasing total resistance

Current in R in the shown circuit D R www Im A just after closing the switch is zero B long after closing the switch is zero C EE R3 R3 just after closing the switch is long after closing the switch is E E R3 R3 E L 50000000 R3 ww C

10 Find the equivalent resistance of the network between the points A and B shown in the figure If A and B are connected to a 13 V battery so that VA V Find a the current in each resistor B b the potential difference Vab V Vb a 19 192 192 152 292 b A B

Seven resistors each of resistance 9 are connected across a 14 V battery as shown below www R IN 1 A 2 R ww WWW ww www R3 R R5 R 14 V Choose the incorrect statement among the following 1 Voltage drop across resistor R is 7 V 2 Current flowing through resistors R3 and R5 is ww R

Use superposition to find the current Is through the 3ft resistor You must use the principle of superposition only to solve this problem You may verify your solution using other methods 24 V 12 VO 492 www 8 0 ww 492 www 30 3A 16 ma

Five resistors R R5 6 02 R R4 3 2 and R3 12 2 are connected with a 12 V battery as shown Then R R R R R wwwwwwwwwwww wwww 1 The equivalent resistance of circuit is 3 3 The voltage drop across R is 6 V 12 V 2 4 The current flowing through resistance R3 is 4 A The current flowing through R2 is 1 A tous

If E denotes the intensity of the electric field the dimensions of the quantity E 0 are those dE dt of A Current B Current density C Electric potential D Electric flux Choose the correct answer below

Two strain gauges are mounted so that they sense axial strain on a steel member in uniaxial tension The 120 V gauges form two legs of a Wheatstone bridge and are mounted on opposite arms e g arms 1 and 4 The gauge factor for each of the strain gauges is 2 and E for this steel is 29 x 106 psi For a bridge excitation voltage of 4 V and a bridge output voltage of 120 V under load i e E 4 V and SE 120 V a Estimate the maximum strain b What is the resistance change experienced by each gauge

A galvanometer having a resistance G and current i flowing in it produces full scale deflection If S is the value of shunt which converts it into an ammeter of range 0 i and S is the value of the S S2 shunt for the range 0 2i Then the ratio will be 1 1 1 i ia 3 2 21 1 2 2 4 21 ia i ia

240 V dc shunt motor takes 10A and 30A at no load and full load respectively It is having armature resistance of 0 4 ohm d field resistance of 120 ohm Considering iron friction and windages losses are negligible Then examine the various rameters 1 armature current at no load and full load condition 2 Back emf at no load condition 3 Back emf at full load condition 4 Ratio of hark emf from no load to full load condition

Two sources of equal emf are connected in series This combination is in turn connected to an external resistance R The internal resistance of two sources are r and 1 1 If the potential difference across the source of internal resistance r is zero then R equals to b 1 11 c 12 11 12 11 d 1 12 111 115

25 Resistance of a resistance thermometer has values 2 71 and 3 7002 at 10 C and 100 C The temperafure at which the resistance is 3 262 is 1 40 C 2 50 C 3 60 C 4 70 C 25 10 34

CE0214 25 Two wires of resistance R and R at 0 C have temperature coefficients of resistance a and a respectively These are joined in series The effective temperature coefficient of resistance is 1 30 E 0 5 100 3 4 2 a 2 R R R R R R R R

22 In a de circuit the direction of current inside the battery and outside battery respectively are a positive to negative terminal and negative to positive terminal b positive to negative terminal and positive to negative terminal c negative to positive terminal and positive to negative terminal d negative to positive terminal and negative to positive terminal

3 a Obtain maximum amount of power transfer in R from the sources using maximum power transfer theorem in the network shown in Fig S 104 SA R www www 212 2A Fig 5 3 b Find the Laplace transform of the given waveform shown in Fig 6 4 0 A

a i An electric kettle contains 600g of water at 20 C The heater in the kettle operates at 240V The specific heat capacity of water is 4200 J kg C The current in the heater is 12 A Calculate the time taken for the temperature of the water to rise to 100 C time 4

3 Show graphically the variations of a Resistance vs potential difference at constant temperature b Electric current vs potential defference at constant tempera

A filament bulb 500 W 100 V is to be used in a 230 V main supply When a resistance R is connected in series it works perfectly and the bulb consumes 500 W The value of R is 1 230 3 269 NEET Phase 2 2016 2 46 4 13 9