Current Electricity Questions and Answers

The circuit was in the shown state from a long time Now the switch S is closed The amount of charge that flown through the switch S is 25x C then the value of x is Assume all the capacitors are uncharged before connecting in the circuit 50 V 4 F 2 F 2 F F

Consider the ladder network shown in figure What should be the value of resistance R so that effective resistance between A B becomes independent of number of elements in the combination B 292 29 222 wwwwwwwwwwww www 292 1 292 3 8 Q 892 892 www www 29 292 wwww 822 292 www ww 292 wwww 2 49 4 16 O 892 www wwwww 292 29 www R

DIFFERENTIAL EQUATIONS PROVIDE FORMULA OF DIFFERENTIALS FOR KVL A piece of electrical component inside a gaming laptop uses a source of electromotive force resistor and inductor If the voltage resistance and inductance are 4sin4t volts 2 ohms and 1 henry respectively what is the current along the circuit after 2 seconds when the initial current applied to the circuit is 0 6 amperes Assume Kirchhoff s Voltage Law applies which states that travelling around any loop circuit the gains and losses of voltage across the elements add up to zero Do not round off intermediate steps Round off the final answer to two decimal places Choose the correct answer from among the given choices 0 03 amperes 0 21 amperes 0 41 amperes 0 45 amperes 0 54 amperes 0 59 amperes 0 95 amperes

Five hundred cells of same emf E and same internal resistance rare connected in series to form a loop in same order without external resistance The potential drop across 199 cell is found to be 199E 500 E 301 E

Find the equivalent resistance of the networks shown in figure between the points a and b b 1 2 r r Question Type Single Correct Type 4r 3 r www r

Q1 define SI unit of electric current Q2 what happens to the resistance of a conductor when it turns into a circular loop Q3 three resistances 1 Ohm 3 ohm and 5 Ohm connected in series with the battery of 20 volt calculate the potential drop across each resistance also find the electric current

Q2 what happens to the resistance of a conductor when it turns into a circular loop Q3 three resistances 1 Ohm 3 ohm and 5 Ohm connected in series with the battery of 20 volt calculate the potential drop across each resistance also find the electric current Q4 which electrical instrument is used to measure the electric current and voltage how they are connected in the circuit also write their properties Q5 five identical resistance are connected in series and after in parallel what do you think at which configuration the current will more follow and why Q6 define electric power and derive the formula for its various form

Comprehension ill In the circuit shown an ideal battery of terminal voltage V 10 V is connected to the circuit Current in the circuit is recorded on changing the value of external resistor R as shown R R R 02 43 1 5 11 R www www 1 R V 10 V R www R amp Value of R and R for the given condition is 1 R 10 02 2 R 602 3 R 512

Solu Example 158 In the network as shown in Fig 3 168 each resistance r is of 2 Find the effective resistance between between points A and B www A Z ww B represe shown shown

The current flowing through the 32 resistor in circuit shown below is 40 V 10 www 1 15 A from a to b 2 15 A from b to a 3 25 A from a to b 110 20 V 302 b 202 www 20

azes ni bolster Charge Flown due to a Time Varying Current The current in a wire varies with time according to relation I 4 21 Determine the quality of charge which has passed through a cross section of the wire during the time t 2s to t 6s

WHICH OF THE FOLLOWING STATEMENTS IS INCORRECT 1 point WHEATSONE BRIDGE CAN BE USED TO MEASURE RESISTANCE FROM TENS TO A FEW HUNDREDS CORRECTLY WHEATSONE BRIDGE CAN BE USED TO MEASURE INTERNAL RESISTANCE OF A CELL WHEATSONE BRIDGE CAN BE USED TO MEASURE VER LOW RESISTANCE PRECISELY WHEATSONE BRIDGE CAN BE USED TO MEASURE GALVANOMETER RESISTANCE INDUCTANCE CAPACITANCE

Four identical cells each of e m f 2 V are joined in parallel providing current to an external circuit consisting two 15 2 resistors joined in parallel The terminal voltage of the equivalent cell as read by an ideal voltmete is 1 6 V Calculate the internal resistance of each cell 1 6 16 2 2 ution potential Total int 1 5 r 2 4 El 7x4 r G Illust The e m f of a cell is E terminal remains 3 v Solution Internal resistar

58 Calculate the equivalent resistance between points A and B in the following circuit 1 75 5 22 ww 22 www 1 92 222 102 www A www B 202 wwwww 202 wwww www 292 www 292 www 152 2 Q 25 6 6

A Galvanometer can be converted into ammeter by connecting Question Type Single Correct Type 1 2 3 4 Low resistance in series High resistance in parallel Low resistance in parallel High resistance in series

39 When a current I flows through a wire the drift velocity of the electrons is V When current 21 flows through another wire of the same material having double the length and double the area of cross section and same temperature the drift velocity of the electrons will be 1 100 8 2 4

Aakash Institute 49 In an electrostatic machine a belt of width w having a surface charge density o travels with velocity v As the belt passes a certain point all the charge are removed and is carried away as an electric current The magnitude of this current is 1 wvo 2 Wa V

In the given figure initially all switches are open and the capacitor has charge q At t 0 switch S is closed alongwith S or S or both The values of currents I 1 at t 0 as shown in figure R 10 If the S and S both are closed and q 1 C S R A I 21 B I 1A C I IA D 1 1A www C 1uF RL 2v So R S R

3 Current of 3 A flows from D to C 4 Both 2 and 3 2 A heater coil connected across a given potential difference has power P Now the coil is cut into two equal halves of its length and joined in parallel Across the same potential difference this combination has power 1 P 3 P 4 2 4P 4 2P

For the circuit shown in figure potential difference of 12 V is applied across AB 292 E wwww 2925 21 www wwwwwwwwwww 32 D 20 F 12 192 ww 2523 12 V Current drawn through cell is Ne Vol 2 2 v V 352 OVA Vcl 3 V 912 A B

Figure shows a network of eight resistors e equal to 20 connected to a 3V battery of negligible internal resistance The current in the circuit is A 3V www b wwww www a 0 25 A b 0 50 A c 0 75 A d 1 0 A

A potentiometer wire AB is 2 m long and has total resistance of 10 2 Galvanometer shows zero deflection at C when switch S is closed and at point D when switch is open If E 10 V and R 9r then CD is equal to X cm Find the value of 20 V Answer ww r

In Figure 1 the battery has negligible internal resistance and E 45 0 V R R2 3 60 2 and R4 3 90 0 What must the resistance R3 be for the resistor network to dissipate electrical energy at a rate of 295 W R R3 R4 R

44 A beam of electrons moving at a speed of 10 6 m s along a line produces a current of 1 6 10 Then the number of elections in 1 metre of the beam is 1 106 2 107 3 1013 4 1019 SET 29 2

5 A potentiometer wire of length 10 m and resistance 102 per metre is connected in series with a resistance box and a 2 volt battery If a potential difference of 100 mV is balanced across the whole length of potentiometer wire then the resistance introduced in the resistance box will be a 1900 2 c 190S2 b 900 d 90N MP PMT 2013 yn 22 10 hod to four times its length then 2

a 4 5 A millivoltmeter of 25 mV range is to be converted into an ammeter of 25 A range The value in ohm of necessary shunt will be b 0 01 fa 0 001 CBSE AIPMT 2012 d 0 05 6 Ig S c 1 If voltage across a bulb rated 220 V 100 W drops by ad value then the percentage of the P V 11 Loroase is Ja F R 9

63 An electrical cable of copper has just one wire of radius 9 mm Its resistance is 5 ohm This single copper wire of the cable is replaced by 6 different well insulated copper wires each of radius 3 mm The total resistance of the cable will now be equal to 1 7 5 ohm 2 45 ohm 11270ohm

72 You are given a wire of length 100 cm and linear resistance of 1 ohm cm If it is cut into two parts sos that when they are in parallel the effective resistance is 24 ohm The lengths of the two parts are 1 30cm 70cm 3 70cm 30cm 2 60cm 40cm 4 20cm 80cm

9 The temperature coefficient of resistance of conductor varies as a T 372 27 If Ro is resistance at T 0 and R is resistance at T then 1 R R 6T 2 2 R 2R 3 27 772 73 m2 31

1 A cell of e m f E and internal resistance r is connected to an external resistance R The variation of potential difference V across the resistance Ras a function of R as shown in the figure is best represented by curve 1 A 0 A B C 2 B R

45 In the circuit given below all resistances are of values 5 ohm each The currents i and i given that the e m f of the cell is 11V are 11V i 50 M Iem i 50 mx 5Q 1 0 6 A 0 2A 3 0 8 A 0 4A 12 50 41 50 2 0 4A 0 6A 4 0 2A 0 4A 50

47 In the circuit R 400 ohm and R 200 ohm If the resistance of the voltmeter V 10 000 ohm Then the voltmeter reading is R R ATT

5 The electrical resistance of a mercury column i a cylindrical container is R The mercury i poured into another cylindrical container with hal the radius of cross section The resistance o the mercury column is 1 R 2 2R 3 16R 4 5R

30 Three wires having resistances 122 222 and 62 are joined in parallel across a battery If a current 0 1A flows through 62 resistor the total current drawn by the combination is 1 0 6A 2 0 3A 3 0 1A 4 1A

Two wires have their lengths in the ratio 1 3 diameters in the ratio 2 3 and their materials have specific resistances in the ratio 2 1 Then the ratio of their resistances is 1 1 3 2 3 1 3 2 3 4 3 2

1 A carbon filament has resistance of 12002 at 0 C What must be the resistance of a copper filament connected in series with carbon so that the combination has same resistance at all temperatures a carbon 7 x 10 4 C a copper 4 x 10 C 1 12092 2 2122 3 602 4 21092

Two large non conducting plates having surface charge densities to and o respectively are fixed d distance apart A small test charge q of mass m is attached to two non conducting identical springs of spring constant k as shown in the adjacent figure The charge q is now released from rest with springs in natural length Then a will neglect gravityl

A conducting wire of cross sectional area 1 cm has 3 x 1023 charge carrier per m If wire carries a current of 24 mA the drift velocity of carriers is 1 5 x 10 2 m s 1 2 0 5 m s 1 3 5 x 10 3 m s 1 4 4 x 10 m s 1

24V 4mH 00000 R W 50002 In given circuit switch is in position a for what value of R will the circuit have a time constant of 10 s 1 2 0 Kn 2 2 5 KQ 3 1 0 KQ 4 None of these 29 24V 4mH 00000 R L 50002 fy my affer s at ff a Hadid i HT 10 us B T R H 2 B NH 1 2 0 KQ 2 2 5 KQ 3 1 0 Kn 4

56 It is required to construct a resistor of 80 ohm resistance having temperature coefficient of resistance 0 0021 C For this purpose wires of two materials of proper cross sectional area are available For first material the resistance is 80 ohm per 100 metre and the temperature coeffi of resistance is 3 x 10 3 C For the second material the corresponding values are respectively 60 ohm per 100 m and 1 5 x 10 3 C Find out the length of the two wires which can be connected in series so as to have the required resistor Ans 40 metre and 80 metre respectively 3 1

The circuit below is made up using identical light bulbs The light bulbs of maximum brightness of the following will be EQ DQ 1 3 4 Correct Answer 2 Your Answer 4 A CD E A B

For the circuit shown in figures what is the current flows from b to a when a and b are short circuited 2 kn B V IBCBE PORC B 0 0004 Vc 1 12 5 mA 3 25 mA O E 25 IB a 40 kn Vc 2 6 25 mA 4 50 mA b

77 The metre bridge shown is in balance position P with of galvanometer and cell will the bridge work If yes what will be balanced condition NEET 2019 ODISHA L If we now interchange the positions Q 1 2 1 yes 12 1 Q 1 1 P www P 1 11 3 yes Q www 12 2 no no null point P 1 4 yes T

A parallel combination of following cells is connected to an external load If all the cells are connected in same polarity then the value of resistance of the external load such that the power transfer to the load is maximum is S No EMFInternal Resistance 1 2 3 4V 40 6 V 40 2V 20 3Q 20 40

500 10 MQ 34 A uniform wire of resistance 92 is joined end to end to form a circle Then the resistance of the circular wire between any two diametrically points is a 6 Kerala CEE 2014 b 3Q e 10 The equivalent resint 693 20 4 ea d R 3 2 2 Q R q HL H

Question No 13 A galvanometer of resistance 50 02 gives full scale deflection at 3 mA current What should be value of shunt so that it can measure a current of 28 m O 30 0 20 0 60 View O 10

The reading of a high resistance voltmeter when a cell is connected across it is 4 2 V When the terminals of the cell are also connected to a resistance of 10 Q the voltmeter reading drops to 4 0 V Find the internal resistance of the cell 200 11 10 20 2

5 4 0 5 15 20 A t s 2 A vehicle is traveling at an initial speed va of 20 mi h when the driver attempts to accelerate as quickly as possible to its maximum speed Given that the vehicle can accelerate according to a 4 8 0 06v ft s Plot the acceleration speed and distance as a function of time for this vehicle

A cell of e m f 4 V and of negligible internal resistance is connected in series with a potentiometer wire of length 400 cm The e m f of a Leclanche cell is found to be balanced at 150 cm from the positive end of the potentiometer wire What is the e m f of the Leclanche cell YOU A 1 V B 1 5 V C O 2 V

58 There is an infinite wire grid with cells in the form of equilateral triangles The resistance of each wire between neighboring joint connections is R The net resistance of the whole grid between the points A and B as shown in Fig 5 296 is a R b Ro B Fig 5 296 C Ro 3 d Ro