Electricity measuring equipments Questions and Answers

The symbolic representation of four logic gates are given below 2009 1 ii iii TII Do a iv i iii c i ii iv O iv The logic symbols for OR NOT and NAND gates are respectively b iv ii i d iii iv ii

3 16 Pote 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 C 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 determined

Q 7 Two tangent galvanometers A and B have coils of radii 8 cm and 16 cm respectively and resistance 8 each They are connected in parallel with a cell of emf 4 V and negligible internal resistance The deflections produced in the tangent galvanometers A and B are 30 and 60 respectively If A has 2 turns then B must have B 18 turns 12 turns Correct Answer 6 turns

200 3 A neutral particle of mass 28 g is at rest in a uniform magnetic field B T At t 0 particle decays into 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 t interaction force Calculate 100

Chandrayan 1 the lunar mission launched by India in 2008 had all gold wiring A particular instrument on board the mission was operating at the same temperature as the space surrounding the Chandrayan at 3 K Instrument specifications demanded that no wire in the instrument should offer a resistance more than 7 m2 All the instruments on Chandrayan were fabricated in ISRO lab at room temperature of 30 C If the radius of all wires in the instrument was 0 1 mm as measured in ISRO lab If the maximum allowable length as measured in ISRO 22 lab of any wire is approximately meter then find 1 Take 1 Assume that resistivity and length of gold wire change linearly with temperature You can use these properties of gold Resistivity at room temperature p 2 2 x 10 m Temperature coefficient of resistivity 0 0032 K Linear thermal expansion coefficient g 1 5 x 10 K

A ample 2 10 Two resistors of resistances R 100 3 ohm and R 200 4 ohm are connected a in series b in parallel Find the equivalent resistance of the a series combination b parallel combination Use for a the relation R R R and for b 11 1 R R R and AR AR AR R2 R R2

are usually made of 1 Metals with low temperature coefficient of resistivity 2 Semi conducting materials having low temperature coefficient of resistivity Metal oxides with high temperature coeffi cient of resistivity 4 Metals with high temperature coefficient c resistivity

In a potentiometer experiment the balancing length for a cell of emf 2 V and internal resistance 1 Q is 3 m Then the balancing length for a cell of emf 4 V and internal resistance 2 without changing the current in potentiometer wire is 3 m 6 m 2m 1 m

A voltmeter has a resistance of G ohm and a range of V volt The value of resistance that must be used in series to convert it into a voltmeter of range nV volt is 1 n 1 G 2 nG 3 3 G n 1 G

If nn and ne be the number of holes and conduction electrons in an extrinsic semiconductor then Question Type Single Correct Type 1 nh ne 2 nh ne 3 ne nh

A galvanometer has an internal resistance of 50 2 and current required for full scale deflection is 1 mA then the series resistance required to use it as a voltmeter with range as indicated in figure is 50 R Gwww 1 950 2 9 k 2 ko 1 V R www 10 V 2 950 2 10 ks 4 None of these

If an ammeter is to be used in place of a voltmeter then we must connect with the ammeter a Low resistance in parallel High resistance in parallel O High resistance in series Low resistance in series Marks 4

You are given a nichrome wire rheosta t 6V battery and ammeter a Draw a circuit diagram by connecting these in series b If ammeter reading is 2A then what will be the intensity of current c In order to change a 6V battery a 12 V battery is connected to the circuit what will be the ammeter reading

The surge absorb installed before the lightning arreste on the line side in order to Answer minimize the post discharge L voltage of lightning arrester reduce the cost of surge B absorber C improve the efficiency of lightning arrester nflect the traveling waves

2 In a step up transformer transformation ratio is 100 The primary voltage is 200 V and input is 1000 watt The number of turns in primary is 100 Calculate 1 Number of turns in the secondary 2 Current in the primary 3 The voltage across the secondary 4 Current in the secondary 5 Write the formula for transformation ratio

21 A half wave rectifier is used to convert PINNA AC n Hz A C into D C then the number of pulses per second present in the rectified voltage is a n c 2n 22 A full wave rectifier is used to convert n Hz A C into D C then the number of pulses per second present in the rectified voltage is b n 2 d 4n a n c 2n b n 2 d 4n 23 The applied A C power to a half wave rectifier is 200W The D C power output obtained is 50W The rectification efficiency is a 12 5 c 37 5 b 25 d 50

a Identify whether the following is a multiplexer or a demultiplexer Define both in your own words Mux or Demux Select Inputs S Data out 44 Data in b In the given 4 to 1 multiplexer if c1 1 and c0 0 then the output M is

A cell is balanced at 100cm of a potentiometer wire when the total length of the wire is 400cm If the length of the potentiometer wire is increased by 100cm then the new balancing length for the cell will be Assume pd across potentiometer wire is constant

Circuit for the measurement of resistance is shown in the figure The is first connected at point Aand potentiometer galvanometer zero deflection is observed at length PJ 10cm In the second case it is connected at a point C and zero deflection is observed at alength 30cm from P the unknown resistance X is P RA ww ww X C

In the experiment of calibration of voltmeter a standard cell of e m f 1 1 Volt is balanced against 440 cm of potentiometer wire The potential difference across the ends of a resistance is found to balance against 220 cm of the wire The corresponding reading of voltmeter is 0 5 volt The error in the reading of voltmeter will be 1 0 15 volt 3 0 5 volt 2 0 15 volt 4 0 05 volt

30 State the advantages and disadvantages of a moving coil galvanometer A moving coil galvanometer M C G has 10 turns each of length 12 cm and breadth 8 cm The coil of M C G carries a current of 125 A and is kept perpendicular to the uniform magnetic field of induction 10 2T The twist constant of phosphor bronze fibre is 12x10 Nm degree Calculate the deflection produced

1 The potential difference across the 100 resistance in the circuit is measured by a voltmeter of 900 2 resistance The percentage error made in reading the potential difference is a 10 9 b 0 1 1092 c 1 0 900 S 100 S2 till d 10 0 V

7 A resistance of 202 is connected across one gap of a metre bridge and unknown resistance greater than 202 is connected across the other gap When these resistances are interchanged the balance point shifts by 20 cm neglecting any end correction the unknown resistance is 1 30 2 40 3 50 4 602

O uit diagrams A B C and D shown below R is a high resistance and S is a resistance of the order of galvanometer resistance G deflection method for finding the resistance and figure of merit of the galvanometer is the circuit The correct circuit corresponding to the half labelled as 2014 A C S www S www G wwww K K K www R 1 Circuit B with G S 3 Circuit D with G K RS R S B D R www www G www K www S K K K 2 Circuit C with G S 4 Circuit A with G RS R S

During an experiment with a meter bridge the galvanomete shows a null point when the jockey is pressed at 40 0 cm using a standard resistance of 90 2 as show in the scale use in the meter bridge is 1 mm The unknown resistance is 2014 Adv ATOS a 60 0 15 2 c 60 0 25 2 40 520 R www 40 0 cm 90 Q www Dan Gleicot 1 b 135 0 56 0 d 135 0 23 Q Isa

To know the resistance G of a galvanometer by half deflection method a battery of emf V and resistance R is used to deflect the galvanometer by angle 0 If a shunt of resistance S is needed to get half deflection then G R and S related by the equation a S R G RG c 2G S b 2S R G RG d 2S G

In the arrangement shown in figure when the switch S is open the galvanometer shows no deflection for 1 L 2 When the switch S is closed the galvanometer shows no deflection for 5L 12 The internal resistance r of 6 V cell and the emf E of the other battery are respectively

A galvanometer has a resistance of 3002 and a current of 2mA is needed to give a full scale deflection What is the resistance needed to convert the galvanometer Into an voltmeter of 0 2 V range A 2002 B 70 2 C 120 2 D 150 2

3 In a potentiometer experiment a wire AB of length 1 2 m is used For the circuit shown the current through galvanometer becomes zero when the jockey is touched at point P If AP 1 0m the resistance per unit length of the wire AB is 22 m A 40 V 19 292 www P A B

A B C D he output of the given circuit in figure Um sin ot O would be zero at all times would be like a half wave rectifier with position cycles in ou would be like half wave rectifier with negative cycles in out would be like that of a full rectifier

P Q lz If we now interchange the positions of galvanometer and cell will the bridge work If yes what will be balance condition l l l 1 yes Ql Plz 3 ves P www P Q 2 no no null point

or Example 23 27 Resistance of a milliammeter is R of an ammeter is R of a voltmeter is R and of a kilovoltmeter is R Find the correct order of R R R and R tonce has to be connected in parallel

3 399 10 ms 1 1 When a potential difference of 1 5 V is applied across a wire of length 0 2 m and area of cross section 0 3 mm a current of 2 4 A flows through the wire If the number density of free electrons in the wire is 8 4 x 1028 m 3 calculate the average relaxation time Given that mass of electron 9 1 x 10 311 electron kg and charge on 1 6 x 10 19

a meter bridge experiment the circuit diagram and the corresponding observation table are shown in figure 2019 SI NO I cm 1 2 3 4 R Q 1000 100 10 1 Which of the readings is inconsistent 2 B 4 A 60 13 1 5 1 0 C 1 R Resistance box E D 3 G Unknown resistance K X

n given circuit determine I I and I 1 2 km k2 10 V 14 k 12 k 14

The length of a wire of a potentiometer is 100 cm and the emf of its standard cell is E volts It is employed to measure the e m f of a battery whose internal resistance is 0 5 Q2 If the balance point is obtained at l 30 cm from the positive end the e m f of the battery is 1 2 3 30E 100 30E 100 5 30E 100 05

paramagnetic sample shows a net magnetization of 8 Am when placed in external magnetic field of 0 6 T at a temperature of 4K When the same sam placed in an external magnetic field of 0 27 at a temperature of 16K the antion will bo

The input signal giver TU voltage gain of 150 is V 2cos 15t 3 corresponding output signal will be 1 300 cos 15t 2 300 cos 15t 5 3 3 75 cos 15t 4 2 cos 2 cos 15 41 3 15t 2 3 5n The Re AIPMT 2015

x Find the value of resistances for the following colour code 1 Blue Green Red Gold Ans 6 5 k2 5 2 Brown Black Red Silver Ans 1 0 k2 10 3 Red Red Orange Gold Ans 2 2 k2 5 4 Orange White Red Gold Ans 3 9 kn 5 5 Yellow Violet Brown Silver

A resistance of R2 draws a current from a potentiometer The potentiometer has a total resistance Ro 2 Figure A voltage V is supplied to the potentiometer Derive an expression for the voltage across R when the slide is in the middle of the potentiometer N C E R T C B S E 2014 Ad Ro www

3 7 with S 9 The resistances in two arms of a metre bridge are R 502 and S respectively When the resistance S is shunted with an equal resistance the new balance length is found to be 1 5 4 where I is the initial balancing length Calculate the value of S RrRB cm B 100 cm ttle

In a common emitter transistor amplifier the audio signal voltage across the collector is 3V The resistance of collector is 3 k If current gain is 100 and the base resistance is 2 kn the voltage and power gain of the amplifier is 1 15 and 200 3 20 and 2000 2 150 and 15000 4 200 and 1000

The resistance of a potentiometer wire is 82 and its length is 8 m A resistance box and a 2 V battery are connected in series with it What should be the resistance in the box if it is desired to have a potential drop of 1 V mm

The output across the diode in the given circuit in figure V sincot ww R 1 Would be zero at all times 2 Would be like a half wave rectifier with positive cycles in output 3 Would be like a half wave rectifier with negative cycles in output 4 Would be like that of a full wave rectifier

16 A dip circle is placed perpendicular to the magnetic meridian then the magnetic needle will align 1 Horizontally 3 In the direction of earth s magnetic field 17 At a place dip angle is known to be 45 The annarent din whom 2 Vertically 4 Perpendicular to earth s magnetic field

In a potentiometer experiment it is found that no current passes through the galvanometer when the terminals of the cell are connected across 125 cms of the potentiometer wire On shunting the cell by a 2W resistance the balancing length reduces to half The internal resistance of the cell is A 4W B 2W C 1W D 0 5W

10V IMQ ww VR BE R 4k www CE NCE T10V 3 2 7 00 V 4 6 00 V y In the given circuit VBE 0 7 V and B 100 then find V CE 1 6 28 V 3 6 5 V

Example A A D 12 1 222 www www 692 20 V 8 V C 22 www G IG 0 11 B ES alqmex3 Pr Fig 23 83 In the figure shown wire AB has a length of 100 cm and resistance 892 Find th balance point length l

32 The reading of the ammeter in the circuit below is 222 22 wwwwwwwww 1 5 A 2 15 A 3 20 A 22 www 22 wwww 20 V 222 A

56 Consider the potentiometer circuit arranged as in figure 32 E29 The potentiometer wire is 600 cm long a At what distance from the point A should the jockey touch the wire to get zero deflection in the galvanometer b If the jockey touches the wire at a distance of 560 cm from A what will be the current in the galvanometer A 12 R 15r G