Current Electricity Questions and Answers

The resistances of the four arms P Q R and Sin a Wheatstone bridge are 10 ohms 30 ohms 30 ohms and 90 ohms respectively The e m f an internal resistance of the cell are 7 volts and 5 ohm respectively If the galvanometer resistance is 50 ohms the current drawn from the cell will beg 1 2 0 A 2 1 0 A 3 02 A 4 0 1 A EDMI NOTE 5 PRO

The equivalent resistance between points A and J and current I in the following circuit will be 552 652 15V I 1 1592 0 5A B E J 31202 F 1202 452 G D www 2402 H 2 152 1A 3 1202 0 5A 4 1202 1A

A galvanom er of resistance G is shunted by a resistance S ohm To keep the main current in the circuit unchanged the resistance to be put in series with the galvanometer is AIPMT Mains 2011 1 2 3 G S G G S G S S G SG

of the potentiometer wire What is the In the circuit shown the ammeter reads 2 A and the voltmeter reads 4 V Find the emf E and the resistance R Assume the voltmeter and ammeter to be ideal 122 E a 202 N 402 R A 1023 302 E3022

20 Four resistances are connected by an ideal battery of emf 50 volt as shown in figure circuit is in steady state then the current in wire AB is 192 202 A 1A B 2A 302 B 50v 402 C SA n D 4 A 2 1 50 500 21

In the given circuit calculate potential difference between A and B D A 2V 2V 20 303 x SHH 303 BU 4V SQ

47 Four identical electrical lamps are labelled 1 5V 0 5A which describes the condition necessary for them to operate at normal brightness A 12V battery of negligible interval resistance is connected to lamps as shown then 12V M 9 M R wwwww A The value of R for normal brightness of each lamp is 3 4 B The value of R for normal brightness of each lamp is 21 4 C Total power dissipated in circuit when all lamps are normally bright is 24W D Power dissipated in R is 21W when all lamps are normally bright

In the circuit shown the current thr same before and after connecting E is 62 www 1 12 V F 12 V 89 ww rough E The value of E F 10 22 www 2 6 V 4 2 V i 2

Five identical lamps each of resistance R 1100 2 are connected to 220 V as shown in figure The reading of ideal ammeter A is 220 V 1 A A 15 R R R A 2 5 R R 2 2 12 A 4 1 A

Resistance of wire AB is 2000 and resistance of voltmeter is 1500 2 If sliding contact is in the middle of wire AB then reading of voltmeter will be 16Volt A 1 3 V 3 10 X 2 6 V 8 V 1 B

Each resistance in the given cubical network has resistance of 122 and equivalent resistance between A and B is 1 A 22 www 5 C 1 22 CO www B 2 D 12 2 A potentiometer has a uniform wire of length 5 m A battery of emf 10 V and negligible internal resistance is

In mixed grouping of cells for maximum current ER A R m nr nr m C mR nr D R r

2 Find the velocity of charge leading to 1 A current which flows in a copper conductor of cross section 1cm and length 10 km Free electron density of copper is 8 5 x 1028 m How long will it take the electric charge to travel from one end of the conductor to the other

PARAGRAPH FOR QUESTIONS 92 93 A car battery with a 12V e m f and an internal resistance of 0 04 is being charged with a current of 50A 580 battery 92 D 16V 93 The potential difference V across the terminals of the battery are A 10V B 12V C 14V The rate at which energy is being dissipated as heat inside the battery is A 100W B 500W C 600W 700W behaves as a load V E iR 14

158 What will be the equivalent resistance of circuit shown in figure between two points A and D CBSE AIPMT 1996 3 10 2 A WWW 2 4 C wwwww 10 W a 10 2 10 2 wwwww 102 b 20 s www 102 c 30 2 10 S2 www B 10 2 www D 10 S2 d 40 2

In the circuit shown determine the magnitude of potential difference between A and D 292 www T10 V 1 5 V 3 20 V 302 A 192 www B 4V 402 20 V wwwwww 2 10 V 4 90 V 602

the figure A 4V potentiometer is used for determination of internal resistance of a 2 5 V cell The balance point of cell in open circuit is 75 cm when a resistor of 4 is used in the external circuit of the cell the balance point shifts to 60 cm length of potentiometer wire The internal resistance of the cell is

In the given circuit when the switch is shifted from position 1 to position 2 find the total heat dissipated in the resistors 10 V K 10 Q2 2 i T 10 V 1022 M 20 nF 30

The value of the resistor R needed in the dc voltage regulator circuit shown here equals A Vi VL nIL V V n 1 IL C B V VL nIL D V V n 1 IL V nl R IL

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference The ratio of heat produced in series and parallel combinations would be

per The number of protons falling on earth s surface unit area per unit time is 1500 If the radius of the earth is 6 4 106 meters the current coming to earth due to these cosmic ray protons is a 1 5 amp c 0 642 amp b d 0 123 amp 6 4 amp

10V 652 2522 3V 3 F HH 100 20V B C Find the change on 3uF capacitor initially it was zero A 6 F B 30 F C 81uF D 21uF PEATE F

150 Two batteries one of emf 18 volts and internal resistance 2 2 and the other of emf 12 volts and resistance 1 n are connected as shown The voltmeter V will record a reading of b 18 volt V 411 2018 41112 020 12V c 15 volt d 14 volt

1 65 A non conducting sphere of radius R has a positive charge which is distributed over its volume with density p Po 1 1 R per unit volume where x is distance from the centre If dielectric constant of material of the sphere is k 1 calculate energy stored in surrounding space and total self energy of the sphere

An electric iron is rated 220 V 2 kW 2018 If the iron is used for 3h daily find the cost of running it for one week if it costs 4 25 per kWh

Kened in the figure shown R is a fixed conducting ring of negligible resistance and radius a PQ is a uniform rod of resistance r It is hinged at the centre of the ring and rotated about this point in clockwise direction with a uniform angular velocity There is a uniform magnetic field of strength B pointing inwards r is a stationary resistance then choose correct statements B R 9 A Current through r is zero 2Bwa B Current through r is 5r C Direction of current in external r is from centre to circumference of ourront in external r is from circumference to centre

4 Reading of A and A are respectively 202 202 2 52 www www A www 2 52 www 352 v 18v www 252 1 2A 1A 2 BO www www 3223 252 www www www www 2 52 2 02 252 2 1A 2A 3 3A 3A 4 1A 1A

In the given circuit diagram the potential difference between A and B is 1 3 V 3 6 1 F 1 6V A 19 4 1 12 20 3 V 2 5 V 4 9 V B

36 Eleven identical wire each of resistance R are connected as shown in the figure The equivalent resistance between the points A and B is 1 7R 12 ZR A B www www www www 7 2 wwwww 5R 6 3R 3

The scale of galvanometer is divided into 150 equal divisions The galvanometer has the current sensitiv ity of 10 divisions per mA and the voltage sensitivity of 2 divisions per mV How can you convert this gal vanometer into a an a ammeter of 6 A per division b voltmeter of 1 V per division is mazig Calculate the galvanometer resistance G value of shunt S to be connected to convert into ammeter and value of series resistance R to be connected to con vert into voltmeter

33 Two cells having the same emf are k connected in series through an external resistance R Cells have internal resistances and 2 2 respectively When the circuit is closed the potential difference across the first cell is zero The value of R is CBSE AIPMT 2006 a 12 d 4 1 b 5 1 2 c 4 1 2 2

10 For the combination of resistors shown in Fig 8 30 find the equivalent resistance between the points a C and D and b A and B C R 302 R 33 02 R ww 302 3Q R 322 R5 D 392 R A B

Current in the network shown in figure is 1 1 A 2 0 5 A 3 2 A 4 5 A 42 www 16 2 10 V www 222

PA 0 50 wwww A 3 2 volt C 1 0 volt How 352 wwww 19 N 0 50 In the circuit shown the current through the 4 ohm resistor is 1 amp when the points P and M are connected to a d c voltage source The potential difference between the points M and N is 2008 M B 1 5 volt D 0 5 volt

A battery consists of 50 cells each of emf 2V and internal resistance 0 202 A variable resistance R is connected to the positive terminal of the battery and the negative terminal to 1442 Another 1000 resistor is connected between the junction of these two series resistances and a point in the battery at a potential of 40V below the positive terminal 40V I 60V I 1000 250 www 1440 Resistance R in the circuit if current in it is 0 5A equals

A potential difference of 200 volt is applied to a coil at a temperature of 15 C and the current is A being the same as before temperature coefficient of resistance a 1 234 C 1 107000 Find the value of

204 The reading of the ideal voltmeter in the adjoining diagram will be B 10 V 10 92 ww 20 92 4 V HH b 8 V d 14 V a 4 V c 12 V In the given circuit the current flowing through the 209

In the circuit shown the effective resistance between the points a and bis 352 2322 202 1 1 5 2 3 25 0 60 4022 6N ww 32 2 652 60 4202 62 2 20 4 3Q

The potential difference VA VB between point A and B in the network shown is 4 A 1 1 V 3 4 V 29 A 12 wwwwwww www 1922 B 22 2 2 V 4 3 V

In the infinite ladder network shown below if R 1 235 then the effective resistance between the points a and b approximately is 5 2 235 R aww be 1 0 145 3 20 R R R R R R 2 R 5 1 4 3 52

Section A Q 1 A 25 w 220 v bulb and 100 w 220 v bulb are joined in series and connected 1 to mains which bulb will glow brighter a 25 w bulb b c both will glow same brightness 100 w bulb d First 25 w bulb then 100 w of steady and uniform

Calculate the currents through each resistance in the given circuit Also calculate the potential difference between points a and b 6 V 52 a A www b 102 10 V 42 8 V

Four resistors are connected in a square formation Two batteries of emf E and 2E are connected along the diagonals as shown in the figure The current flowing in the resistor R is R R 4E A C 3R 3E 2R D E R 3E R R www R m EN www R 2E

A two way switch S is used in the circuit shown in the figure First the capacitor is charged by putting the switch in position 1 Calculate heat generated across each resistor when the switch is shifted to position 2 60V wwwww 40 wwww 100 602 wwwww www 312

4ed 27 In the circuit shown the ratio 2 is equal to 402 ww 5 V I 1923 1 1 1 3 4 3 322 12 89 322 5 4 L 2 V 292 2 2 1 A A 3 4 2 5

50 A small town with a demand of 800 kW of electric power at 220 V is situated 15 km away from an electric plant generating power at 440 V The resistance of the two line wires carrying power is 0 5 22 km The town gets power from the lines through a 4000 230 V step down trans former at a substation in the town a Estimate the line power loss in the form of heat b How much power must the plant supply assuming there is negligible power loss due to leakage c Characterize the step up transformer at the plant C B S E Sample paper C B S E 2003

You have been provided with four 400 ohm resistors each The number of ways in which these can be combined to have different equivalent resistances is a seven different combinations and seven different equivalent resistances b eight different combinations and seven different equivalent resistances c nine different combinations and eight different equivalent resistances d ten different combinations and nine different equivalent resistances

a 3 If the length of the filament of a heater is reduce by 10 the power of the heater will Increase by about 9 Increase by about 11 Increase by about 19 Decrease by about 10 b c d

5 In the given circuit the reading of voltmete shown in the figure is 7 V 1 4 V 600 22 www V 1200 S2 A 300 2 2 14 V 3 Medi

In the given circuit AB is a uniform wire of 102 and length 1 m It is connected to series arrangement R 100 O G B of cell of e m f 2 V and negligible internal resistance and a resistor R Terminal A is also connected to an electrochemical cell e of em f 100 mV and a galvanometer G In this set up a balancing point is obtained at 40 cm mark from A Calculate the resistance R If 2 were to have an c m f of 300 mV where will you expect the CRSE