Electricity measuring equipments Questions and Answers

Two light bulbs in the circuit have rating A 24 V 48W and B 24V 36W as shown 127 O When switch is closed bulb A delivers 24 watt B delivers 18 watt O 12 O When switch is open A delivers 9 watt B delivers 12 watt approximately When switch is open A delivers 24 watt B delivers 18 watt approximately When switch is open A delivers 6 watt and B delivers 9 watt approximately A B

d 10A mass of 3 kg is placed on the massless piston of area 10 cm of a cylindrical vessel containing a gas Find the fractional change in surface area of sphere if its bulk modulus is 2 x 104 N m and placed in the given vessel 1 0 5 7 2 1 5 3 1 4 Zero 11 The thermal stress developed in the rod if it is held C See

Design a phase shift oscillator for given figure for fo 350Hz Assume C 0 1 F R1 22kQ R1 www Rf Vcc A O Vec C 16 Choose R 1kQ and Rf 1MQ www Choose R 2kQ and Rf 620kQ Choose R 1kQ and Rf 720kQ Choose R 3 3kQ and Rf 1MQ CO C www

Design a Wheatstone bridge circuit the values resistances are P 1000 Q 100 R 2005 and S 200 2 The battery has an emf of 5V ar negligible internal resistance The galvanometer has a current sensitivity of 10mm micro Amp a an internal resistance of 100 Q Calculate the deflection of galvanometer and the sensitivity c the bridge in the terms of deflection per unit change in resistance

9 b A 4 pole d c shunt generator with a shunt field resistance of 100 2 and armature resistance of 1 2 has 378 wave connected conductors in its armature The flux per pole is 0 02 Wb If a load resistance of 10 2 is connected across the armature terminals and the generator is driven at 1000 r p m calculate the power absorbed by the load

7 The combination of two bar magnets makes 5 oscillation second when like poles tied together while 1 oscillation second when unlike poles are tied together The ratio of magnetic moments of the magnets 1 2 3 SE IR RE 13 12 12 13 25

2 The figure shows part of certain circuit The magnitude of potential difference between points C and B is C 3A 1 8V www 192 12V www www 292 50 3V www www 4 Q 69 4A 2 10V 2A B

Identify the correct statements regarding power MOSFET You can select multiple correct options Power MOSFET has lower switching lobses but have more on resistance Power MOSFET is current controlled device with positive temperature coefficient In power MOSFET secondary breakdown occurs because it has positive temperature coefficient Power MOSFET in higher voltage ratings have more conduction loss

28 50 In a potentiometer circuit a cell of EMF 1 5 V gives balance point at 36 cm length of wire If another cell of EMF 2 5 V replaces the first cell then at what length of the wire the balance point occurs Final Results 0 1 60 cm 67 2 21 6 cm 33 3 64 cm 00 A CO

Q 4 In any industry it is having three phase 440V 50Hz ac supply and carrying some electrical equipments for working on a machine In a manager room there is a 4 pole induction motor and its slip is to found be 0 02 Then determine following a Rotor speed relative to the stator structure b Frequency of rotor currents at standstill

Which of the following is true for step up transformer Primary voltage is high Secondary current is small Primary current is small O Both 1 3 min

student is working on 3 phase 50 Hz 4 pole induction motor having slip 5 Then selecting the value slip determine following Determine frequecy of rotor cu OPTIONS 3 5 Hz 2 5 Hz

PASSAGE A student is working on 3 phase 50 Hz 4 pole induction motor having slip 5 Then selecting the value of slip determine following Choose the correct option Marks 2 Determine the rotor frequency if supply frequency is changed from 50 Hz to 60 Hz at slip 5 OPTIONS 5 Hz 3Hz 2Hz

5 Calculate the r m s value the form factor of a periodic voltage having the following values for equal time intervals changing suddenly from one value to the next 0 5 10 20 50 60 50 20 10 5 0 5 10 V etc What would be the r m s value of sine wave having the same peak value

Each question carries 10 Marks 10 X When two two port networks are connected in parallel which parameter should be found and why

4 A potentiometer wire of length L and a resistance r are connected in series with a battery of e m f E and a resistance r An unknown e m f E is balanced at a length of the potentiometer wire Re AIPMT 2015 The e m f E will be given by LE r 1 r r Er I 1 LE r 2 Tr El 4

The voltage across a load is controlled by using the circuit diagram shown in Fig 87 The resistance of the load and of the U Fig 87 R potentiometer is R The load is connected to the middle of the potentiometer The in put voltage is constant and equal to U Determine the change in the voltage across the load if its resistance is doubled

Circuit for the measurement of resistance by potentiometer is shown The galvanometer is first connected at point A and zero deflection is observed at length P J 10 cm In second case it is connected at point C and zero deflection is observed at a length 30cm from P Then the unknown resistance X is nR fill the value of n P www R ww A M

A voltmeter of resistance 1000 2 gives full scale deflection when a current of 100 mA flow through it The shunt resistance required across it to enable it to be used as an ammeter reading 1A at full scale deflection is 1 10000 2 3 222 N 2 9000 4 111 22

A galvanometer can withstand safely a maxin converted into voltmeter of range 40 V by connecting in series an external resistance of 3880 Q The resistance of galvanometer is O 600 O 1200 440 0 360

A galvanometer having 30 divisions has a current sensitivity of 20 A per division It has a resistance of 25 ohms a How will you convert it into an ammeter measuring upto 1 A b How will you convert this galvanometer into a voltmeter reading upto 1 V

02 To convert galvanometer into voltmeter the a high resistance is connected in series with galvanometer b high resistance is connected in parallel with galvanometer c low resistance is connected in series with galvanometer d low resistance is connected in parallel with galvanometer

in the shown network of resistive wire current enters at O and leaves out at A Resistances Ro4 Ros Roc RoD RAB Rec RcD R0A R Choose the correct option s Equivalent resistance between 0 and A is 7R 15 7R Equivalent resistance between 0 and A is 8 Potential of points A and Care same Potential of points B and D are same 54 1 6 11 16 21 26 31 36 Not Answ 2 7 12 17 22 27 32 37

A galvanometer can withstand safely a maximum current of 10 mA It is converted into voltmeter of range 40 V by connecting in series an external resistance of 3880 Q The resistance of galvanometer is O 60 Q O 120 Q O 440 36 0

10 With a resistance R connected in series with a galvanometer of resistance 100 92 it acts as a voltmeter of range 0 to 10 V To double the range a resistance of 1000 Q is to be connected in series with R Then the value of R in is a 1100 b 1000 c 900 d 800

PHYSICS 35 The resistance of the metre bridge AB in given figure is 4 92 With a cell of emf 0 5 V and rheostat resistance R 2 2 the null point is obtained at some point J When the cell is replaced by another one of emf the same null point J is found for R 6 22 The emf is JEE Main 2019 A A M 6 V 1 0 6 V 3 0 3 V 36 A galvanometer having a resistance of 20 2 and 30 divisions on both sides has figure of merit 0 005 ampere division The resistance that should be connected in series such that it can be used as a voltmeter upto 15 volt is JEE Main 2019 1 100 2 2 125 2 3 80 2 4 120 2 37 In the circuit shown the potential difference between A and B is JEE Main 2019 592 WW 192 www 1 92 www R 2 0 5 V 4 0 4 V 192 N www 1 V 2 V HH 3 V 10 52 www B C B A 1 6 V 2 3 V 3 2 V 4 1 V 38 In the experimental set up of metre bridge shown in the figure the null point is obtained at a distance of 40 cm from A If a 10 2 resistor is connected in series with R the null point shifts by R R Divisions of Ask 1 60 2 3 40 2 39 The galvanometer deflection when key K is closed but K is open equal 8 see figure On closing K also and adjusting R to 5 9 the deflection in The resistance of the R 220 2 www galvanometer becomes galvanometer is then given by Neglect the internal resistance of battery JEE Main 2019 R akas Med ndations Service 42 ARCHIVE JEE Main 2 30 92 4 20 2 K B K ww 2 2592 4 12 2 In a meter bridge the wire of length 1 m has a non uniform cross section such that the variation dR dl of its resistance R with length is dl dR 1 Two equal resistances are connected as shown in the figure The galvanometer has zero deflection when the jockey is at point P What is the length AP JEE Main 2019 B

Listen When attempting to measure current flow the ammeter should be inserted directly into the circut so as to force each and every charge through the meter itself 1 True 2 False

Slip Rings Brush Load Q 52 The energy conversion taking place in the above set up is a Magnetic energy into electrical energy b Electrical energy into magnetic energy c Electrical energy into mechanical energy d Mechanical energy into electrical energy Q 53 The output of the device is known as ac because S a It continuously changes its magnitude only b It continuously changes its direction only c It continuously changes its magnitude and direction d It continuously changes its magnitude and periodically Q 54 The working principle of the above device is a Faraday s law of electromagnetic induction b Lenz s law c Both the above d Kirchoff s laws Q55 In the above device instead of full slip rings if half slip ri known as a A C b DC

X is unknown resistance as shown in the potentiometer circuit The length of wire AB is 100 cm When P and Y are connected then balance is obtained at 40 cm and when P and Z are connected then balance is obtained at 58 8 cm The value of X is Vo A 100 Q Y X Z B Sop Im

0 A galvanometer shows full scale deflection when I mA current passes through it How can t galvanometer be converted into an ammeter to measure a current upto a maximum of 10A A 0 0522 is to be connected in parallel with the galvanometer B 0 012 is to be connected in parallel with the galvanometer C 0 0552 is to be connected in series with the galvanometer D 0 012 is to be connected in series with the galvanometer

In a circuit instantaneous voltage and c urrent are V 15 sin 314t volt and i 5 cos 314t ampere respectively The nature of circuit and the power dissipated in complete cycle is A Inductive zero B Capacitive 75 W C Inductive 3 W D Capacitive zero

98060 Pre Medical Physics 51 QUIPOTENTIAL 50 Potential inside a charged spherical shell is 1 uniform WEEN FIELD 2 proportional to the distance from the centre 3 inversely proportional to the distance

Figure shows a circuit in which three identical diode are used Each diode has forward resistance of 20 2 and infinite backward resistance Resistors R R R3 50 2 Battery voltage is 6V The current through R3 is A 50mA C 60 mA B 100 mA D 25 mA Dww D R D2 KH D3 www M R

11 A cycle wheel with 20 metallic spokes each 1 m long is rotated with speed of 60 rad s in a plane normal to horizontal component of earth s magnetic field BH 0 5 G at a place The emf induced between axle and rim of wheel is NCERT Pg 215 1 1 5 mV 3 3 0 mV 2 12 3 mV 4 0 75 mV

44 In the meter bridge shown negative temperature coefficient of resistance Neglecting the variation in other resistors when current is passed for some time in the cirucit balance point should shift towards A R www 1 A 2 B 3 First A then B G C X wwwwww B

The given potentiometer has its wire of resistance 10 When the sliding contact is in the middle of the potentiometer wire the potential drop across 2 resistor is 20 VIL A A 10 V B 5 V 202 www B

The graph shows variation of v with change in u for a mirror Points plotted above the point P on the curve are for values of v 45 A A Smaller then f C Larger then 2f B Smaller then 2f D Larger than f For a concave mirror if virtual images formed the graph between m and u is of the form P m B m

24 The resistance of a tungsten filament at 150 C is 133 2 What will be its resistance at 500 C The temperature coefficient of resistance of tungsten is 0 0045 per C 1 258 9 2 300 Q 3 158 9 4 58 Q

8 Two short magnets have equal pole strength but one is twice as long as the other The shorter magnet is placed at 20 cm in tanA position from the compass needle The longer magnet must be placed on the other side of the magnetometer for no deflection at a distance equal to 1 20 2 1 3 cm 2 20 2 2 3 cm 3 40 cm 4 20 cm

A galvanometer of resistance 50 0 gives full scale deflection at 3 mA current What should be value of shunt so that it can measure a current of 28 mA 30 20 60

Read the following text and answer Q53 to Q55 questions on the basis of the same MOVING COIL GALVANOMETER A galvanometer is a device which is used to detect the presence of current The moving coil galvanometer consist of a coil with many turns and free to rotate about a fixed axis in a uniform magnetic field Q The galvanometer works on the principle O a That a rotating coil when placed in a uniform magnetic field emf is induced in the coil O b That when a current carrying coil is placed in a uniform magnetic field it experiences a torque c Of mutual inductance 1 point d None of these

1 point A resistance of 5 ohms is connected across the gap of a Meter Bridge and an unknown resistance greater than 5 ohms is connected across the other gap When these resistances are interchanged the balance point shifts by 50 cm Neglecting any correction what is the unknown resistance The length of the wire is 150 cm a 3 ohms b 10 ohms c 7 ohms d 5 ohms

Please explain each and every option in detail also why fo rth is wrong 1 Choose the correct statement than pervers breakdows vondaryo transforentifier circuit must be sufficiently higher peak A C voltage at of 2 In full wave rectifier bothcycles are reversed at output 3 In centre tap full wave rectifier four diodes are used 4 If half wave rectifier only positive cycle is present at output

Obtain the output voltage across the 15k resistance measured with the help of a voltmeter VM having an internal resistance of 30 kQ How much is the percentage loading due to inte resistance offered by the VM 100v 15 KJ2 www www 15K2 30K VM

In a meter bridge the balancing length from the left end standard resistance of two ohm is in the right gap is found to be 40 cm The value of unknown resistance is 040 13 CI 020

A galvanometer of resistance 50 Q gives full scale deflection at 3 mA current What should be value of shunt so that it can measure a current of 28 mA 0 30 0 20 0 60

Online Mock Test Series for NEET 2020 43 A cell is balanced on a length of 150 cm of a potentiometer wire Now a resistance of 50 is connected in parallel to the cell then the balance point is obtained at 100 cm The value of internal resistance of cell is 1 2 52 2 2012 3 1022 4 25 2

In the experiment of calibration of voltmeter a 1 1 V standard cell gets balanced at 440 cm length of wire The balancing length corresponding to a potential difference between the end of a resistance comes out to be 190 cm A voltmeter shows 0 5 V for this potential difference The error in the reading of voltmeter will be 5k x 10 V Find the value of k

A moving coil galvanometer of resistance 200 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 79 9950

A galvanometer may be converted into ammeter or voltmeter In which of the following cases the resistance of the device will be largest Assume the maximum range of galvanometer 1 mA 1 An ammeter of range 10 A 2 A voltmeter of range 5 V 3 An ammeter of range 5 A 4 A voltmeter of range 10 V