Electricity measuring equipments Questions and Answers

The r m s value of induced voltage in a coil of 50 turns each of area 30 sq cm rotating at 1000 r p m about an axis at right angles to magnetic field is B 5 x 104 Wb m 4 A 555 mV C 5 55 mV 55 5 mV 55 mV B D

3 Two equal resistances when connected in series to a battery consume electric power of 60 W If these resistances are now connected in parallel combination to the same battery the electric power JEE Main 2019 Asumed will be 1 60 W 3 120 W 2 30 W 4 240 W

9 A potentiometer wire AB having length L and resistance 12r is joined to a cell D of emfe and internal resistance r A cell C having emf and internal resistance 3r is connected The length AJ at which the galvanometer as shown in fig shows no deflection is JEE Main 2019 1 3 1124 12 A Der N m 3r B 2 24 4 13 L 24

A 100 turn closely wound circular coil of radius 10 cm carries a current of 3 2A A uniform horizontal magnetic field of strength 2T is turned on The axis of the coil is initially in the direction of the field The coil rotates through an angle of 90 under the influence of the magnetic field The moment of inertia of the coil is 0 1 kg m What is the field at the centre of the coil

A uniform metallic wire has a resistance of 18 2 and is bent into an equilateral triangle Then the resistance between any two vertices of the triangle is JEE Main 2019 1 4 2 2 12 2 3 8 52 4 20

In the potentiometer circuit shown in figure the internal resistance of the 6V battery is 102 and length of the wire is 100 cm When AD 60 cm the galvanometer shows no deflection The emf of the cell C is the resistance of the wire AB is 202 s A 1 0 7 V 6 V 102 502 m the D For ons B 2 0 8 V

OO hem is first calculated assum point like charges a ing them t th Two charged spheres are kept at a finite centre to centre spacing as shown in the figure The force of electrostatic interaction between them is first calculated assuming them point like charges at their respective centres and then force is measured experimentally If the calculated and the measured values are F and F respectively which of the following conclusion can you certainly draw a ff F F for like charges and F F for unlike charges both the spheres must be made of insulating materials b If F F for like charges and F F for unlike charges both the spheres must be made of conducting materials e Irrespective of their materials F F for like charges and F F for unlike charges d Irrespective of their materials F F for like charges and F F for unlike charges Two charged spheres are kept at a finite cent

46 The circuit shown in figure employs a constant current source of 8 A which alway maintains the current through a load by varying its emf The value of R for which receives maximum power in the circuit in ohms is 182 wwwwww 322 8 A www 32 R 152 www

A moving coil galvanometer of resistance 20 gives a full scale deflection when a current of 1 mA is passed through it It is to be converted into an ammeter reading 20 A on full scale deflection If a shunt wire of 0 005 Q only is available then what resistance should be connected in series with the galvanometer coil 99 955 Q O 79 995 Q 59 295 Q

Moving Charges and Magnetism a 210 mA c 420 mA 92 In the given circuit a galvanometer with a resistance of 70 2 is converted to an ammeter by a shunt resistance of 0 05 2 total current measured by this device b 155 mA d 75 mA 0 05 2 70 52 is a 0 88 A b 0 77 A c 0 55 A d 0 99 A 93 A galvanometer having a resistance of 50 2 gives a full scale deflection for a current of 0 05 A The length in metres of a resistance wire of area of cross section 3 x 10 cm that can be used to convert the galvanometer into an ammeter which can read a maximum of 5 A current is Specific resistance of the wire p 5 x 1022m a 9 b 6 c 3 d 1 5 96 A voltmeter which can measure 2V is constructed by using a galvanometer of resistance 122 and that produces maximum 94 The conversion of a moving coil galvanometer into a voltmeter is done by a introducing a resistance of large value in series b introducing a resistance of small value in parallel c introducing a resistance of large value in parallel d introducing a resistance of small value in series 95 A galvanometer of resistance 10 2 gives full scale deflection when 1 mA current passes through it The resistance required to convert it into a voltmeter reading upto 2 5 V is a 24 9 2 b 249 2 c 2490 2 d 24900 2 R 91 deflection for the current of 2 mA then the resistance Ris a 888 92 c 898 2 97 The value of current in the given circuit if the ammeter is a galvanometer with a resistance RG 50 92 is b 988 2 d 999 2 a 0 048 A c 0 061 A 2 V 5 V b 0 023 A d 0 094 A 98 A galvanometer coil has a resistance of 15 2 and the metre shows full scale deflection for a current of 4 mA To convert the meter into a voltmeter of range 0 to 18 V the required resistance is a 5885 2 in series c 5885 2 in parallel b 44852 in series d 4485 92 in parallel 99 A galvanometer of resistance 50 2 is connected to a battery of 3 V along with a resistance of 2950 2 in series A full scale deflection of 30 divisions is obtained in the galvanometer In order to reduce this deflection to 20 divisions the resistance in series should be a 6050 2 c 5050 2 b 4450 92 d 5550 2 100 The range of voltmeter of resistance 300 2 is 5 V The resistance to be connected to convert it into am ammeter of range 5 A is a 152 in series c 0 1 S2 in series b 12 in parallel d 0 1 92 in parallel

5 The mean length of an object is 5 cm Which of the following measurements is most accurate A 4 553 cm C 4 9 cm B 5 22 cm D 5 5 cm 45 A 5 B 2 C 4 D 3 au dus 5 cm 9 al llauriell sy ang d ay A 4 553 cm C 4 9 cm B 5 22 cm D 5 5 cm

21 In the lead storage battery 1 a reversible reaction can occur to recharge the battery 2 lead is oxidized to create a flow of electrons 3 lead forms the cathode when it is being reduced

Under the influence of a uniform magnetic field a charged particle moves with a constant speed v in a circle of radius R The time period of rotation of the particle 2009 2007 depends on R and not on v is independent of both v and R depends on both v and R depends on v and not on R

To make a voltmeter from a galvanometer which the following is required A A high resistance is a connected in parallel B A high resistance is connected in series C A low resistance is connected in parallel D A low resistance is connected in series

In the circuit diagram given below AB is a uni form wire of resistance 15 ohm and length one metre It is connected to a series arrangement of cell of emf 2 0 V and negligible internal resis tance and a resistor R Terminal A is also con nected to an electrochemical cell 2 of emf 75 mV and a galvanometer G In this set up a balancing point is obtained at 30 cm mark from A Calculate the resistance of R If 5 were to have an emf of 300 mV where will you expect the balancing point to be V XAB PAB PAR N ta RAB 15 LAB Im A E wi R www B

When a resistance of 20 is connected across a 32 cell a current of 0 5 amp flows If the resistance is increased to 50 the current increases to 0 25 ampere The internal resistance of the cell is 1 0 50 1 00 3 1 50

A milliammeter of resistance 5 ohm gives a full scale deflection for a current of 15 mA If the milliammeter is to be used to measure current upto 1 5 A then the resistance that must be attached to the milliammeter is usixs A 0 0505 9 C 5 05 2 B D 0 505 505

Galvanometer G having full scale deflection current lg and resistance R is use in combination with resistances to form an ammeter whose range i is given in Column II Match the entries in Column l with the entries in Column II Column l Q1 Q2 Q3 Q4 Q1 Q2 Q3 A1 R www 2R www www R R www R www R www 4R www A2 A3 A4 A5 Column II A1 i is maximum A2 3 ig A3 2 ig A4 6 ig A5 4 ig

A B and C are voltmeters of resistance R 1 5R and 3R respectively as shown in the figure When some potential difference is applied between X and Y the voltmeter readings are V VB and VC respectively then AIPMT 2015 X A 1 VA VB VC 3 VA VB VC B Y 2 VA VB Vc 4 VA VB VC

Consider a thin permanently interface of magnetic medium of permeability and vacuum If the magnetic medium near a point on the interface makes an angle with the normal to the interface The angle made by the magnetic field with the normal is a 0 tan 0 b tan c d Ho l l 10 cose tan tan

Q No 16 To increase the current sensitivity of a moving coil galvanometer we should 1 3 4 decrease number of turns in coil decrease area of cross section of the coil increase torsional constant of spiral springs None of the above Correct Answer 4 Status unattempted 27

31 If only 51 through a galvanometer then the shunt 1th required is R and if only of the main 11 voltage is to be developed across the galvanometer then the resistance required R Then a of the main current is to be passed 1 500 R R b 50 9 c 500 3 d 500

End corrections in a meter bridge arise due to extra resistances at the two ends of the wire If the end corrections in both ends of a meter bridge are 4 cm and the balancing length below the known resistance 300 is measured to be 20cm then the true value of the unknown resistance in is

of e m f E is connected to a resistance R for time t and the amount of heat generated in it is H If the resistance R is replaced by another resis tance R and is connected to the cell for the same time t the amount of heat generated in R is 4H Then the internal resistance of the cell is 1 2R R 2 3 R R R 2 R 2 R R 2 R R 4 R R 2 R R R 2 R R R R R

Fig of Q 45 54 21 4 51 PM A DUPL E E Mark only one oval wwww R www i When the key K is open how does the balance point change if the current from the driver cell decreases Mark only one oval shifts towards right shifts towards left remains unchanged first shifts towards right and then towards left s docs google com forms d 10 T14 2NW7po1y3416jbj0thxxoFmz2mA 210 yLro edit HALF YEARLY EXAMINATION B 55 ii When the key K is closed how does the balance point change if F 21 29 increased keeping the current from the driver cell constant shifts towards right shifts towards left remains unchanged first shifts towards right and then towards left 56 iii Sensitivity of potentiometer can be increased by Mark only one oval increasing the current flowing through the wire decreasing the length of the wire decreasing the current flowing through the wire 1 point 1 point

To draw the reverse characteristics of a zener diode and to study its voltage regulation characteristics using a variable load Breakdown region should be identified in the graph Percentage voltage regulation has to be calculated for given load currents

94 In a potentiometer of 10 wires the balance point is obtained on the 7th wire To shift the balance point to 9th wire we should a decrease resistance in the main circuit b increase resistance in the main circuit c decrease resistance in series with the cell whose emf is to be measured d increase resistance in series with the cell whose emf is to be determinad

EXAMPLE 2 14 A 502 loss less transmission line is connected to a load of 50 j50 2 The maximum voltage measured on the line is 50 V Find the power delivered to the load and the peak voltage at the load end of the line

In a NPN transistor common emitter mode 1010 electrons enter the emitter in 1 s Only 1 of electrons are lost in the base what will be collector current 1 584 mA O 1 54 MA O 1 273 MA

200 T At t 0 particle decays into 3 A neutral particle of mass 28g is at rest in a uniform magnetic field B two particle of equal mass and one of them having charge 3 C Both of them move in separate paths lying in the plane perpendicular to magnetic field B At later time t the particle collides Neglecting the interaction force Calculate t 100

6 The pieces of Aluminium and Silicon are placed in closed room at 280 K temperature then which of the following statement is corrent Initial temperature is 300 K A Resistance of both decreases B Resistance of both increases C Resistance of Aluminium decreases but resistance of silicon increases D Resistance of Aluminium increases but resistance of silicon decreases

15 In the following question choose proper pairs from Column 1 and Column 2 Column 1 Column 2 a b c d Zener Diode Photo Diode LED Solar cell A a p B aq C a r b q b r b q c r CS C P p q r s In photography In control of traffic light In cd player In Voltage Regulated power supply d s d P d s

a 0 88 A 3A galvanometer having a resistance of 50 2 gives a full scale deflection for a current of 0 05 A The length in metres of a resistance wire of area of cross section 3 x 10 cm that can be used to convert the galvanometer into an ammeter which can read a maximum of 5 A current is Specific resistance of the wire p 5 x 10 22 m a 9 b 6 c 3 d 1 5 The conversion of a moving coil galvanometer into a

A galvanometer of resistance 70 2 is converted to an ammeter by a shunt resistance r 0 03 2 The value of its resistance will become a 0 025 92 c 0 035 2 b 0 022 02 d 0 030 2

A micrometer has a resistance of 1000 and a full scale range of 50 A It can be used as a voltmeter or a higher range ammeter provided a resistance is added to it Pick the correct range and resistance combination s 0 E 50 V range with 10k resistance in series 10 V range with 200k resistance in series 5mA range with 10 resistance in parallel 10mA range with 1k0 resistance in parallel

98 In a potentiometer the balancing with a cell at length of 220 cm On shunting the cell with resistance of 3 22 balance length becomes 130 What is the internal resistance of this cell a 4 502 b 7 89 c 6 30 d

00 A potentiometer wire of length 100 cm has a resistance of 10 2 It is connected in series with a resistance and a cell of emf 2 V and of negligible internal resistance A source of emf 10mVis balanced against a length of 40 cm of the potentiometer wire What is the value of external resistance a 790 52 b 890 2 c 990 2 d 1090 2 4

The following set of figures shows components of a mechanical system in figure 1 and assembled system in figure 2 There are two small balls of mass m and 2m a massless tube of length L a spring of natural length L and an inextensible massless rope of length L In the assembly the string holds the two balls in position keeping the spring compressed The arrangement lies on a smooth horizontal table x y plane as shown At this moment the velocity of centre of mass of system is voi and angular velocity is ok Take this moment as t 0 y axis hollow tube 2 m 2V0 2 C mL Vo 1 2m Figure 1 The kinetic energy of the system in centre of mass frame is A maL B moL No x L string reeeeeeeeeeee spring m D mL Angular momentum of the system about origin of the table frame where the point 2m is located at origin at t 0 is L A 3 mL 0 L B 0 0 2m Figure C mexL 1 ML v 0 LK x axis D mL vo L

mtG Objective NCERT P 44 Combine three resistors 5 2 4 5 92 and 3 22 in sach a way that the total resistance of this combinations a 12 52 b 13 52 c 14 592 d 16 50 maximum 45 The total resistance in the pall

23 The output characteristics of a transistor is shown in the figure When VCE is 10 V and le 4 0 mA then value of Bac is lc in ma 9 2 2 468 10 12 14 Ver in volts 60 A 50 A 40 A 30 A 20 A 10 A

Let there be a spherically symmetric charge distribution with charge density varying as p r P uptor R and p r 0 for r R where r is the distance from the origin The electric field at a distance r r R from the origin is given by A P T 38 4 R 4xp r5 r

In the circuit shown the reading of the ammeter ideal is the same with both switches open as with both closed find the value of resistance R in ohm 10092 1 600 www R A WH 3000 1 5V 2 800 Q 5092

Consider the protection system shown in figure below The circuit breakers numbered from 1 to 7 are of identical type A single line to ground fault with zero fault impedance occurs at the mid point of the line at point F but circuit breaker 4 fails to operate stuck breaker If the relays are coordinated correctly a valid sequence of circuit breaker operation is 1 2 Transmission Line 3 5 BUS C te boo 7

The figure shows a two generator system applying a load of PD 40 MW connected at bus 2 G Bus 1 PG1 Bus 2 testbook PD 40MW The fuel cost of generators G and G2 are C PG1 10000 Rs MWh and C PG2 12500 Rs MWh and the loss in the line is P loss Pu 0 5P Where the loss G G1 Pu coefficient is specified in pu on a 100 MVA base The most economic power generation schedule in MW is

1 A potentiometer is connected across A and B balance is obtained at 64 0 cm When potenti lead to B is moved to C a balance is found cm If the potentiometer is now connected ac and C a balance will be found at a c A 8 0 cm 64 0cm B b C 56 0 cm

19 A common emitter amplifier circuit is shown in the figure below For the transistor used in the circuit the current amplification factor B 100 Other parameters are mentioned in the figure dc 2017 Gujarat RB 220k 2 BE BC We find that a VBE 18 2 V V b VE 18 5 V V BE BC R 4 7k 92 1 5 mA HIDE Vcc 24 V 3 45 V and amplifier is working 2 85 V and amplifier is not working C VRE 20 7 V VRC 3 75 V and amplifier is not working BE BC d VBE 21 5 V V 2 75 V and amplifier is working

17 06 2021 Sr Super60 All Jee Adv 2019 P1 GTA ci angos V and V oro put in the left hand and right hand gone in ya IIT Academy Then two

A cell of constant e m f is first connected to a resistance R and then connected to a resistance R If power delivered in both cases is equal then the internal resistance of the cell is 1 R R 3 R R 2 2 4 R R2 R R 2

In the shown arrangement of a meter bridge distance of galvanometer jockey on wire AB from A corresponding to null deflection of the galvanometer is x What would be its value if the radius of wire AB is doubled R 4 R www w AXC 2x 4x Y G B

an ini speed v ap Three charges 0 1 coulomb each are placed on the corners of an equilateral triangle of side 1 m If the energy is supplied to this system at the rate of 1 kW how much time would be required to move one of the charges onto the midpoint of the line joining the other two