Current Electricity Questions and Answers

Consider the following circuit where the capacitor is initially empty zero initial conditions the capacitance C is C 1mF and the voltage across the capacitor is vc t 5e 10t sin 3t 2 u t V C i Vin VC 1 R1 www i2 R2 www

18 12 The velocity of charge carriers of current about 1 ampere in a metal under normal conditions is of the order of a a fraction of mm sec b velocity of light c several thousand metres second d a few hundred metres per second 3 6 Limitations of Ohm s Law 13 The resistance of a discharge tube is a non ohmic b ohmic c zero Current 14 From the graph between current I and voltage V is shown Identify the portion corresponding to negative resistance d both b and c 1999 BC E A Voltage a CD b DE c AB d BC a 470 k2 5 c 4 7 k2 5 1991 3 7 Resistivity of Various Materials 15 The color code of a resistance is given below 1997 Yellow Violet Brown Gold The values of resistance and tolerance respectively are b 47 k2 10 d 470 92 5 NEET 2020 16 A carbon resistor of 47 4 7 kQ2 is to be marked with rings of different colours for its identification The colour code sequence will be a Violet Yellow Orange Silver b Yellow Violet Orange Silver c Yellow Green Violet Gold d Green Orange Violet Gold NEET 2018 17 Identify the set in which all the three materials are good conductors of electricity a Cu Hg and NaCl b Cu Ge and Hg c Cu Ag and Au d Cu Si and diamond WtGNEET AIPMT Chapterwise Topicwise Solutions Physic 3 8 Temperature Dependence of Resistivity 18 Which of the following graph represents the variation of resistivity p with temperature T for copper a c P P NEET 202 19 The solids which have the negative temperatu coefficient of resistance are a metals c semiconductors only d insulators and semiconductors b NEET 202 20 Specific resistance of a conductor increases with a increase in temperature b increase in cross section area d c increase in cross section and decrease in lengt d decrease in cross section area 200 21 Copper and silicon is cooled from 300 K to 60 K t specific resistance a fuse c inductor a b insulators only a decreases in copper but increases in silicon b increases in copper but decreases in silicon c increases in both d decreases in both c 3 9 Electrical Energy Power 22 Which of the following acts as a circuit protectie device a R 2b a R 6b 23 NEET 201 The charge flowing through a resistance R vari with time t as Q at bt where a and b are positi constants The total heat produced in R is a R b b b conductor d switch 200 d a R 3b NEET I 201 1994 24 Two cities are 150 km apart Electric power is se from one city to another city through copper wire The fall of potential per km is 8 volt and the avera resistance per km is 0 5 92 The power loss in the wire is a 19 2 W b 19 2 kW c 19 21 d 12 2 kW 201

the circuit shown the current through the 42 resistor is 1 A when the points P and M are connected to a d c voltage source The potential difference between the points M and N is P 42 3Q 0 52 0 5 Q N 12 M AIPMT Prelims 2008 2 1 5 V

value of the single equivalent resistor that could be used to replace the entire resistor network Assume the following values for the circuit elements 12 0 V Ra 18 00 Rb 4 50 Re 12 0 Rd 26 02 Re 10 02 Rj 12 70 W Rb W Rd W Image size S M L Max

73 When the key K is pressed at time t 0 then which of the following statement about the current in the resistor AB of resistance 1000 of the given circuit is true 24 Amm B K 1000 Q 1 F 1000 2 1 oscillates between 1 mA and 2 mA 2 Att 0 2 mA and with time it goes to 1 mA 3 1 mA at all t 4 2 mA at all t

C 2 28 In following diagram boxes may contain resistor or battery or any other element 1A I 10 V 10 A 1A i Electric power output across box 10 V 1Q B then determine in each case a E m f of battery b Battery is acting as a source or load c Potential difference across each battery d Power input to the battery or output by the battery e The rate at which heat is generated inside the battery f The rate at which the chemical energy of the cell is consumed or increased g Potential difference across box b

A heater coil connected across a given potential difference has power P Now the coil is cut into halves and joined in parallel Across the same potential difference this combination has power 1 P 2 4P 3 P 4 4 2P

6 In the electric network shown when no current flows through the 402 resistor in the arm EB the potential difference between the points A and D will be 292 F ww A 2V 292 www 1 9V a 6V b b 4V 3V 3V E www 402 1H B 3V D ww C R c c 5V d 4V

22 In the situation shown the potential difference across the cell of smaller e m f is 12 V 1 2V 12 www 10 V ww 112 www 292 2 4V

1 Charge Q passing through a cross section of conductor at an instant is given by Q 0 5 t C where t is in second Current through the conductor at t 1 s is 1 Zero 3 2 A 2 1 A 4 1 A D

54 Two cells having the same emf are connected in series through an external resistance R Cells have internal resistances r and r r r respectively When the circuit is closed the potential difference across the first cell is zero The value of Ris see badk AIPMT Prelims 2006 1 1 1 3 1 12 2 1 1 2 4 r 1

A letter A is constructed of a uniform wire with resistance 1 02 per cm The sides of the letter are 20 cm and the cross piece in the middle is 10 cm long The apex angle is 60 The resistance between the ends of the legs is close to a 50 00 c 36 7 b 102 d 26 72

03 A resistance wire connected in the left gap of a metre bridge balances a 10 resistance in the right gap at a point which divides the bridge wire in the ratio 3 2 If the length of the resistance wire is 1 5 m then the length of 1 Q2 of the resistance wire is a 1 0 x 10 2 m b 1 0 x 10 m c 1 5 x 10 m d 1 5 x 10 2 m

The equivalent resistance of the resistors connected in the circuit as shown in following figure between the point A and Bis A R 3R 9R 2 R ww 3R www 3R W 3R B

Two bulbs of rated power 60 W and 100 W and same specified voltage 220 V are connected in series to a 440 V DC source 60 W bulb gives more brightness 100 W bulb gives more brightness 100 W bulb will get fused 60 W bulb gets fused

3 27 A piece of wire is cut into four equal parts and the pieces are bundled together side by side to from a thicker wire Compared with that of the original wire the resistance of the bundle is A The same C 1 8 as much B 1 4 as much D 1 16 as much

7 In the circuits shown below the readings of th voltmeters and the ammeters will be i 10 Q2 wwwww V 10 V Circuit 1 4 a V V and i b c V V and i d 102 wwwww 1022 www iz V A 10 V Circuit 2 V V and i 1 V V and i 1 NEET 2019

In the circuit given below current flowing in 6 Q resistor is 2 A The emf E of the battery is 2 A 692 4922 ww 84 V 24 V www 302 ww E 0 50 96 V ww ww 292 hr m 2 522 ww

An ideal voltmeter Vand ideal ammeter A are connected in a circuit as shown in the figure If the reading of the voltmeter is 32 V the reading of ammeter will be 4 A O 8 A 10 A 892 A

or has been 3 29 Variation of current and voltage in a cond shown in figure 3 304 The resistance of the conductor is A 40 392 I A A 5 4 3 2 1 0 61 1 1 1 2 3 Figure 3 304 I B 292 20 D 19 44 4 5 6 V volt 1 St C

The charge flowing through a resistor R 20 varies with time as q 3 4t The heat produced in 2 second is about where q is in C and tis in s 330 3 J 341 3 J 345 2 J DOC

3 7 Resistivity of Various Materials 5 The color code of a resistance is given below um Yellow Violet Brown Gold The values of resistance and tolerance respectively a a 470 k2 5 b 47 ks 10 c 4 7 km 5 d 470 5 NEET 2020

An N P N transistor in a common emitter mode is used as a simple voltage amplifier with a collector current of 4mA The terminal of a 8V battery is connected to the collector through a load resistance R and to the base through a resistance RB The collector emitter voltage VCE 4V base emitter voltage VBE 0 6V and base current amplification factor B 100 Calculate the value of R in A 4 IB RB B 3 www VBE ww Ic RL VCE VCE E C 2 8V D 1 KQ

Six similar bulbs are connected as shown in the figure with a DC source of emf E and zero internal resistance The ratio of power consumption by the bulbs when i all are glowing and ii in the situation when two from section A and one from section B are glowing will be a 2 1 b 4 9 c 9 4 d 1 2 A 00 E B 00

If a cell of constant E M F produces the same amount of the heat during the same time in two in dependent resistors R and R when they are separately connected across the terminals of the cell one after the another find the internal resistance of the cell

plz explain its answer In the potentiometer arrangement shown the driving cell D has emf E and internal resistance r The cell C whose emf is to be measured has emfE 2 and internal resistance 2r The potentiometer wire is 100 cm long If balance is obtained the length AJ 1 A This question has multiple correct options B C 1 50cm 1 D e r I 50 cm C 8 2r balance will be obtained only if resistance of AB is r J B

3 51 A 10m long wire of resistance 2002 is connected in series with battery of EMF 3V and negligible internal resistance and a resistance of 10 2 The potential gradient along the wire is A 0 02V m 0 2V m LO bac B 0 1V m D 1 2V m

10 Find the effective resistance between points A and B www 192 192 www 1 92 1 3 1 c wwwwwwww 1 22 192 19 122 www 12 A D www 192 19 In wwww www 19 192 Lo wwww 192 B 12 RAL PABD 3 1 2 3 1 192

Why the direction is from Q to P 100 In the circuit shown the current in the 10 resistor is directa 6V 392 a 1 3 A from P to Q c 0 13 A from Q to P P 20 www www 192 Q 32 9V JEE Main 2015 b O A d 0 13 A from P to Q

iv The diagram above shows a circuit with a 12 v d c power supply an ammeter and two 4 2 resistors connected in parallel Calculate the total resistance of the circuit v Calculate the current flowing through the ammeter vi Calculate the current flowing through each resistor VIII De effect ct nese two 12 V HH 492 492 A

A galvanometer has a resistance of 25 n and given a full state deflection for a current of 10 mA This galvanometer is to be modified to give range of 1 25 A and 50 V what are resistances of shunt and high resistance needed to achieve this

If the ratio of the concentration of electrons that of holes in a semiconductor is 7 5 and the ratio o currents is 7 4 then what is the ratio of their drift velocities 2006 5 A C 7 5 B D 8 5 4

Figure shows a common emitter amplifier with B 100 What is the maximum peak to peak input signal v for which is distortion free output may be obtained Assume VBE 0 and r 2012 a 40 mV b 60 mY 500 k 10 V 2 k2 Vo 6 801

ix A solenoid of inductance L with resistance r is connected in parallel to a resistance R A battery of EMF E and of negligible internal resistance is connected across the parallel combination as shown in the figure 5 121 E L r momm R Figure 5 121 a Current through the solenoid after the switch is opened at t 0 b Amount of heat generated in the solenoid R r

Let resistance of PN junction be R then I Illustration 9 What is the value of current I in given circuits Solution I 20 10 10 R 30 10 1 A 20V 1002 www 8 100 Kimy 100 a in

18 In the circuit shown in figure 32 W13a E F G and H cells of emf 2 1 3 and 1V respectively The resistances 2 1 3 and 1 are their respective internal resistances Calculate a the potential difference between B and D and b the potential differences across the terminals of each of the cells G and H Con 1 V are A 192 D F 2 V E 202 Git 3 V 202 W a 32 B in 1 V 12 C A 1 V H 192 F i 2V E TEVILO A M 2 I DALE VERGI 202 1 12 5252 GIL 3 V b w 3Q B 1 V 152 1 C

A laptop and a hair trimmer of rating 40 W 220V and 10W 220V respectively ar e connected in series and across a sou rce of 440 volt The fuse of which of the two devices is likely to burn if current is made to flow for say 10 minutes justify your answer

acitance variable Current power alue of power viii A box contains L C and R When 250V DC voltage is applied to the terminals of the box a current of 1A flows in the circuit When an AC source of 250V 2250 rad s is applied across the box a current of 1 25A flows through it It is observed that the current rises with frequency and becomes maximum at 4500rad s Find the values of L C and R in the box Also draw the circuit diagram 4 2502 1 F H

In the circuit shown the reading of the Ammeter is doubled after the switch is closed Each resistor has a resistance 1 Q and the ideal cell has an e m f 10 V Then the Ammeter has a coil resistance equal to ww 1 Question Type Single Correct Type 20 ww 2 10

iv The equivalent inductance of two inductors is 2 4H when connected in parallel and 10H when connected in series What is the value of inductance of the individual inductors Neglect mutual inductance between the two inductors 4H 6H

Consider a Wheatstone bridge with resistance and capacitance connected as shown Find the condition on the resistance and the capacitance such that the bridge remains balanced at all times A R B R G R D C2 C

In an p n junction diode change in temperature due to heating 1 Does not affect resistance of p n junction 2 Effects only forward resistance 3 Effects only reverse resistance 4 Affects the overall V I characteristic of p n

A circuit is composed of ten identical batteries and a resistor R 10 2 Each batteries has an emf of 2 V and internal resistance 0 1 22 The voltage difference across the resistor R is E 2x10 1 3 V 3 6 V 2 2 V 4 Zero May 1

Potential at a point is 500 volt How much work we will have to perform to shift electron from to this point B D 500J 500 500eV 500eV

a A resistor has colour band sequence Orange Violet orange gold and another resistor Orange Violet orange silver Find the range in which its value must lie so as to satisfy the manufacturer s tolerance of both resistor

Three identical bulbs are connected in series as shown When switch is closed A B 3 C Question Type Single Correct Type Q 1 Both bulbs A and B become dimmer 2 Both bulbs A and B become brighter Brightness of bulbs remains unchanged 4 A becomes brighter and B becomes dimmer

92 Current Electricity nichrome is 1 7 x 104C 1 The temperature of nichrome now is NCERT Pg 105 1 700 C 3 850 C 10 The incorrect statement among the following statements is INCERT Pg 111 2 750 C 4 900 C 1 Emf of a cell is the potential difference between its positive and negative electrodes in an open circuit 2 Internal resistance of dry cells is much higher than common electrolyte cells 3 The terminal potential difference of a cell can be zero 4 When current passes from positive to negative terminal of a cell inside it terminal potential difference is less than its emf 11 When a current of 2 A flows in a battery from its negative to positive terminal the potential difference across it is 12 V If a current of 3 A is flowing in opposite direction it produces a potential difference of 15 V the emf of the battery is NCERT Pg 111 1 12 6 V 2 13 5 V 3 14 0 V 4 13 2 V 12 In the combination of two cells in parallel by joining positive terminals together and similarly two negative ones the value of Eq in circuit is NCERT Pg 115 8 V 15 F 6 V F 252 www 292 ww R 1 7 A 3 2 A 13 When a metal conductor connected to right gap of meter bridge is heated the balancing point from left end NCERT Pg 120 1 Shifts towards left 2 Shifts towards right 3 Remains unchanged 4 Shift to zero position 14 Resistance P Q S and R are arranged in clockwise cyclic order to form a balanced wheatstone bridge The ratio of electric power consumed in the branches P Q and R S is INCERT Pg 109 1 1 1 2 R P 2 10 A 4 8 A cal IIT s 4 Q S A battery of e m f 5 V and negligible interna resistance is connected across the diagonally opposite corners of a cubica network consisting of 12 resistors of networ each of resistance 1 2 The current alon INCERT D

45 A galvanometer of resistance 100 2 gives full scale deflection at 10 mA current What should be the value of shunt so that it can measure a current of 100 mA 1 11 11 Q 3 9 9 Q 2 1 1 Q 4 4 4 Q

8 In a potentiometer of 8 wires the balance point is obtained on fifth wire To shift balance point to 6th wire we should NCERT Pg 122 1 Decrease resistance in main circuit 2 Increase resistance in main driver circuit 3 Decrease resistance in series with cell whose emf is to measure 4 Taking driver battery with higher emf

47 A 10 m long potentiometer wire is connected to a battery having a steady voltage A Leclanche cell is balanced at 4 m length of the wire If the length is kept the same but its cross section is doubled the null point will be obtained at 1 8 m 2 4 m 3 2 m 4 None of these