Current Electricity Questions and Answers

51 The relation between voltage sensitivity o and current sensitivity o of moving coil galvanometer is Resistance of galvanometer G a C 0 G G ov ov 0 b ov G d G 0 1 MOSTER

100 If two wires having resistances R and 2R 10 both joining in series and in parallel then ratio of heat generated in this situation applying the same voltage is A 2 1 C 2 9 B 1 2 D 9 2 S 3R P

Q 52 A tungsten filament bulb is connected to a variable voltage supply The potential difference V is varied and the current I and steady temperature T of the filament is recorded A graph is plotted for In VI Vs In T Find the slope of the graph Assume that temperature of filament T To atmospheric temperature A V Filament

10 The circuit shown in the diagram extends to the right into infinity Each A branch resistance is denoted by r What is the resistance between the terminals A and B 5 1 r 2 c 5 1 r a 5 1 r b 2 d 5 1 r Bow ww my

1 A nickel wire when connected across an ideal battery temperature of the wire increases by A0 100 C after a long time If the wire of half length is used by how many degrees will its temperature increase Specific resistance of nickel depends on temperature according to the law p po 1 a 0 where a 0 0050 K and po is the resistivity at the initial temperature 1 162 1 200 40 1 126 0 1 2 22

2 A non conducting cylindrical rod is inserted within two coils of insulated wires as shown in the given figure A battery is connected to coil 1 while a galvanometer is connected to coil 2 Coil 1 Coil 2 1 Coil 2 will move towards it 3 the pointer of the galvanometer will remain at zero 4 the pointer of the galvanometer will a deflection 2 coil 2 will move away from it

3 The circuit consists of a current source I 10 A paralleled by G 0 1 S and a voltage source E 200 V with 100 series resistance Find Norton equivalent circuit to the left of terminals AB Ans IN 15A FTh 20 M2 E R 8

O terminal voltage When I current is drawn from cell then terminal voltage V is less than it s e m f i e V E Ir When cell is discharging Current inside the cell is from cathode to anode IS Current I ye smjha do E IR Ir V Ir V E Ir I r R When current is drawn from the cell potential difference is less than the emf of th is the current drawn from the cell smaller is the terminal potential difference When is drawn from a cell its terminal potential difference is reduced appreciably When cell is getting charand k

In the circuit shown the battery is ideal with emf V The capacitor is initially uncharged The switch S is closed at t 0 The current in DE at time is R A R L2RC LLL R Correct Answer

When the key K is pressed at time t 0 then which of the following statement about the current I in the resistor AB of the given circuit is true 2V KA B 1000 2 C 1 F 1000 W 631 is a I oscillates between 1 mA and 2 mA b at t 0 I 2 mA and with time it goes to 1 mA c I 1 mA at all t d I 2 mA at all t 1995

In a building there are 15 bulbs of 45 W 15 bulbs of 100 W 15 small fans of 10 W and 2 heaters of 1 kW The voltage of electric main is 220 V The minimum fuse capacity rated value of the building will be 1 10 A 2 25 A 3 15 A 4 20 A

A single phase transformer 100 kVA 1000 V 100 V 50 Hz has a voltage drop of 5 across its series impedance at full load Of this 3 is due to resistance The percentage regulation of the transformer at full load with 0 8 lagging power factor is 1 4 8 2 6 8 3 8 8 108

4 Two batteries with e m f 12 V and 13 V are connected in parallel across a load resistor of 10 22 The internal resistances of the two batteries are 1 and 2 2 respectively The voltage across the load lies between 1 11 4 V and 11 5 V 3 11 6 V and 11 7 V 2 11 7 V and 11 8 V 4 11 5 V and 11 6 V

0 An aluminium wire of diameter 0 24 cm is connected in series to a copper wire of diameter 0 61 cm The wires carry an electric current of O A Find i current density in the aluminium wire ii drift velocity of electrons in the copper wire Given the number of electrons per cubic meter volume of copper is 8 4 X 1028 Ans 2 2 X 106 Am 3 7 X 104 ms

48 A galvanometer of resistance 202 and having full scale deflection for a current of 100 mA can be converted into a volt meter of range 5 Volt by connecting a resistance R in series with galvanometer The resistance R is 1 98 S 3 50 2 52 4 48 Q

A conducting rod of square cross section is bent in a semi circular shape of radius r as shown in figure Length of side of cross section is equal to a Resistivity of material is p The resistance of rod across its end will be

A galvanometer has an internal resistance of 50 92 and current required for full scale deflection is 1 mA GR R R ww ww 1 m 1 V 41 Find series resistance required for range of 1 volt 1 9000 3 950 Q 10 V 100 V 2 1000 4 900 9

Consider the circuit shown with key opened The key is closed at t 0 Capacitance of one of the shown capacitors is x uF For what value of x the galvanometer does not show any deflection 4 F Xu F key 49 www www 22

c 6 37V d IIV 41 In an a c circuit the potential difference across an inductance and resistance joined in series are respectively 16V and 20V The total potential difference of the source is a 20V c 31 9V 2 In an AC circuit and I b 25 6V d 53 5V

d 8mF 57 In the figure shown three AC voltmeters are connected at resonance a V 0 c V 0 A nuro V R V V ooooo L b V 0 1 d V V 0 C

Q16 Physics If V 12 V and VB 8 V then 652 A C E A B C D 352 252 192 V 56 V VB 68 V Vc 52 V VB 48 V B D

SolveLancer Test In the above figure a current of 2A flows through A towards right Considering this circuit to be part of bigger circuit and A A as ideal ameter then find reading of A and direction of current SolveLancer Test 1202 a 2A Leftward b 8A Rightward c 4A Rightward d 7 2A leftward www 652 www 3002 1602 ww A

36 Arrange the following materials in the increasing order of their resistivity Copper Platinum Silver Aluminum 1 Copper Silver Platinum Aluminum 2 Silver Copper Aluminum Platinum 3 Aluminum Platinum Silver Copper Aluminum Copper Silver

Q 86 In the circuit shown switch S is kept closed and the circuit is in steady state a Find reading of the ideal voltmeter b Now the switch is opened Find the reading of the voltmeter immedi ately after the switch is opened c Fid the heat dissipated in resistance R after the switch is opened E A 3R C ellee V G S wwww R D ellee B

37 In the network of five resistors what should be the value of v such that effective resistances between points y a and b does not change 1 x only 3 5x only a X ww www X y quind X ww www ww X b 2 4x only 4 y can have any value

figure shown what is the potential difference between the points A and B and between B and C respectively in steady state 3 F 16 3 F 20 2 www B 1 F 100 V 1 F HH 1 F HE A a VAB VBC Vac 100 V b VAB 75 V VBC 25 V 25 Y V 75 V 10 2 C

average current does this rotating charge represent A 2 ampere current flows in a uniform conductor which has 1 x 1024 free electrons per metre What is th average drift velocity 1 1 25 m s 3 3 x 10 m s 2 125000 m s 4 1 25 x 10 5 m s If the circuit in the above question i e Q 3 is a 20 feet long wire in your automobile approximately ho long would it take an electron to travel from the negative terminal to the positive terminal of the battery 1 1 second 2 2 hours 4 6 days 3 1 week

To study the dependence of current I on the potential difference V across a resistor R two students used the two set ups shown in the figure A and B respectively They kept the contact point I in four different positions marked i ii iii and iv in the two figures A Student A R Student B iv F A R wwwwwww Student A What will be the position of contact I when for the two students the readings of 1 ammeter and ii voltmeter will be maximum ii iii iv Voltmeter Voltmeter reading is reading is maximum at i maximum at iv Student B Ammeter Reading is Maximum at i Ammeter Reading is Maximum at iv r

4 nR 20 The electric resistance of a certain wire of iron is R If its length and radius are both doubled then 1 The resistance will be doubled and the specific resistance will be halved 2 The resistance will be halved and the specific resistance will remain unchanged 3 The resistance will be halved and the specific resistance will be doubled 4 The resistance and the specific resistance will both remain unchanged

When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value its resistance will becomes 1 Two times 2 Four times 3 Eight times 4 Sixteen times

2 A capacitor and a coil in series are connected to a 6 volt ac source By varying the frequency of the source maximum current of 600 mA is observed If the same coil is now connected to a cell of emf 6 V and internal resistance of 2 22 the current through it will be a 0 5 A b 0 6 A c 1 0 A d 2 0 A

50 Calculate the net resistance between A and B R R 1 3 3R 4 4R 7 A www R R R www R www R R R 2 R R 5R 6 4 R B 55

Two identical capacitors are connected in the circuit shown C is charged to 100 V and switch S is shifted from position 1 to position 2 The negative terminal of C is connected with the positive terminal of C Find the work done by the battery If the polarity of C were reversed what work would have been done by the battery 36 C 10 F Sw C 10 F 20 100 V

D The electron of a hydrogen atom revolves round the proton in a circular nth orbit of radius 2 r on h me with a speed v n 2 a e e 2 2 nh current due to the circulating charge is proportional to AMU 2012 c e 5 The b e 3 d e6 plied across an X ray tube what will be

Consider the four circuits shown in the figure below In which circuit power dissipated maximum Neglect the internal resistance of the power supply 1 E FI R www R www R 70 www R 2 ET wwwwwww R R M an

For different values of resistance R power consumptions in Rare given Then which of the following values are not possible a 2 W c 8 W 1 Only c 3 a b c 4 V WW 12 you R b 5 W d 4 W 2 b c 4 All

The voltage drop across a forward biased diode is 0 7 V In the following circuit the voltages across the 10 ohm resistance in series with the diode and 20 ohm resistance are K 10 V 1 0 70 V 4 28 V wwwww 10 92 www 20 22 10 2 2 3 58 V 4 28 V

A dielectric slab with 500 mm x 500 mm cross section is 0 4 m long The slab is subjected to a uniform electric field of E 6ax 8ay kV 6 x mm The relative permittivity of the dielectric material is equal to 2 The value of constant is 8 85 10 12 F m The energy stored in the dielectric in Joules is

36 A galvanometer of resistance RG is to be converted into an ammeter with the help of a shunt of resistance R If the ratio of the heat dissipated through galvanometer and shunt is 3 4 then 3 a R RG 4 RG c 9R 16 4 b RG R 16R 9 d RG

22 A conductor with rectangular cross section has as shown in figure dimensions a x 2a 4a Resistance across AB is x across CD is y and across EF is z Then A a x y z c y z x E 4a D F 2a a B b x y z d x z y 23 Which of the following has the maximum resistance

3 a 22 B b Calculate og 4 46 Find equivalent resistance between A and D 12 182 182 292 ww ww E b 32 www A c R 20 D 122 1 92 www www 1 2 192 F c 192 d 20 IN 2 d 52

c JE d None of these 17 The variation of current I and voltage V V across a resistance R is as shown in figure The variation of power P with current I is best shown by which of the following graph

a 30 Q b 40 C 15 Power generated across a uniform wire connected across a supply is H If the wire is cut into n equal parts and all the parts are connected in parallel across the same supply the total power generated in the wire is a H 7 c nh b n H d H

A galvanometer can be used as a voltmeter by connecting a Question Type Single Correct Type 1 High resistance in series 2 Low resistance in series 3 High resistance in parallel

a Someone watches TV on average 6 hours each day The TV is connected to a 220 Volt voltage so that the electric current flow through the TV is 0 5 Amperes If the electric company charges Rs 5 per kWh Determine the cost of using electric energy for TV for 1 month 30 days b In a house there are 4 lamps of 20 Watt 2 lamps of 10 Watt 3 lamps of 40 Watt are used 5 hours every day If the electric company charge Rs 5 per kWh find the cost of using electric energy during 1 month 30 days

The diagram below in fig shows a cell of emf 2 volt and internal resistance r 1 ohm to an external resistance R 4 ohm The ammeter A measure the current in the circuit and the voltmeter V measures the terminal voltage across the cell What will be the readings of the ammeter and the voltmeter when i key K is open ii key K is closed

A resistor is connected across a 15 V source What is the current in the resistor if the color code of the resistor is red orange orange silver A 110 V lamp dimming circuit is controlled by a rheostat and protected from excessive current by a 1 5 A fuse To what minimum resistance value can the rheostat be set without blowing the fuse Assume a lamp resistance of 50 ohms

Three 150 W 220V bulbs are connected first in parallel and then in series Each time the combination is connected to a 220 V supply The power drawn by the combination in each case respectively will be Question Type Single Correct Type 1 450 W 50 W 2 50 W 450 W 3 100 W 3000 W

A cell of emf 1 8 V and internal resistance 2 ohm is connected in series with an ammeter of resistance 0 7 ohm and resistance of 4 5 ohm as shown in figure A 0 7 2 292 4 5 a What would be the reading of the ammeter b What is the potential difference across the terminals of the cell

11 One end of a Nichrome wire of length 2L and cross sectional area A is attached to an end of another Nichrome wire of length L and cross sectional area 2A If the free end of the longer wire is at an electric potential of 8 0 volts and the free end of the shorter wire is at an electric potential of 1 0 volt the potential at the junction of the two wires is equal to a 2 4 V c 4 5 V b 3 2 V d 5 6 V