Physics Questions and Answers September 17, 2022

A short electric dipole has a dipole moment of 16 x 10 C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60 with the dipole axis is 1 4 0 9x10NmC (1) zero (3) 200 V (2) 50 V (4) 400 V

A ball is thrown vertically downward with a velocity of 20 ms from the top of a tower. It hits the ground after some time with a velocity of 80 ms. The height of the tower is (g 10 ms) (1) 300 m (2) 360 m (3) 340 m (4) 320 m

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 9 of the resistance wire is (1) 1.5 x 10 m (3) 1.0 x 10 m (2) 1.0 x 10 m (4) 1.5 x 10 m

When a uranium isotope a neutron, it generates (1) 3Kr 103 36 91 (3) Zr 235 92 U is bombarded with Kr, three neutrons and 36 (2) 44 Ba 56 (4) 10Kr 36

A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is (Ho 4 x 107 Tm A1) (1) 3.14 x 105 T (3) 3.14 x 104 T (2) 6.28 x 104 T (4) 6.28 x 105 T

The average thermal energy for a monoatomic gas constant and T, absolute is (kB is Boltzmann temperature) (1) KBT 7. 2 3 (3) kB T (2) kB T 5 (4) KBT

A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of the water in the capillary is 5g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is (1) 20.0 g (3) 5.0 g (2) 2.5 g (4) 10.0 g

The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is (c speed of electromagnetic waves) (1) 1 c (2) c 1 (3) 1 1 (4) 1 c

Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is (1) 6.00 x 107 rad (2) 3.66 x 107 rad (3) 1.83 x 107 rad (4) 7.32 x 107 rad

A wire of length L, area of cross section A is hanging from a fixed support. The length of the wire changes to L when mass M is suspended from its free end. The expression for Youngs modulus is (1) (3) MgL A(LL) Mg(LL) AL (2) (4) MgL AL MgL AL1

The energy required to break one bond in DNA is 1020 J. This value in eV is nearly (2) 6 (1) 0.006 (3) 0.6 (4) 0.06

In a certain region of space with volume 0.2 m the electric potential is found to be 5 V throughout. The magnitude of electric field in this region is (1) 5 NC (2) Zero (3) 0.5 NC (4) 1 NC

The mean free path for a gas, with molecular diameter d and number density n can be expressed as (1) 1 2nrd 1 (3) 2nnd 1 (2) 2 nnd 2 1 (4) 2nnd

An electron is accelerated from rest through a potential difference of V volt. If the de Broglie wavelength of the electron is 1.227 x 10 nm, the potential difference is (1) 104 V (3) 10 V (2) 10 V (4) 10 V

In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases to 7 Hz. If the frequency of A is 530 Hz, the original frequency of B will be (1) 537 Hz (3) 524 Hz (2) 523 Hz (4) 536 Hz

A 40 F capacitor is connected to a 200 V, 50 Hz ac supply. The rms value of the current in the circuit is, nearly (1) 25.1 A (3) 2.05 A (2) 1.7 A (4) 2.5 A

The increase in the width of depletion region in a pn junction diode is due to (1) increase in forward current (2) forward bias only (3) reverse bias only (4) both forward bias and reverse bias

The Brewsters angle it for an interface should be (1) ip 90 (2) 0 i 30 (4) 45 i 90 (3) 30 i 45

The phase difference between displacement and acceleration of a particle in a simple harmonic motion is (1) Zero (3) 3 2 rad (2) rad (4) KIN 2 rad

A spherical conductor of radius 10 cm has a charge of 3.2 x 107 C distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere 1 9x10 NmC 41 0 (1) 1.28 x 107 NC (2) 1.28 x 104 NC (3) 1.28 x 105 NC (4) 1.28 x 106 NC

The capacitance of a parallel plate capacitor with air as medium is 6 F. With the introduction of a dielectric medium, the capacitance becomes 30 F. The permittivity of the medium is (80 8.85 x 102 C N m) (1) 5.00 C2 N1 m2 (2) 0.44 x 1013 C N m (3) 1.77 x 1012 C N1 m2 (4) 0.44 x 1010 C N m2

Taking into account of the significant figures, what is the value of 9.99 m 0.0099 m (1) 9.9 m (3) 9.98 m (2) 9.9801 m (4) 9.980 m

T A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is If instead C is removed from the circuit, the phase difference is again between current and 3 voltage. The power factor of the circuit is 3 (1)1.0 (3) 0.5 (2) zero (4) 1.0

Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled (1) zero (2) doubled (3) four times (4) onefourth

A charged particle having drift velocity of 7.5 x 104 ms is an electric field of 3x1010 Vm, has a mobility in m V s of (1) 2.25 x 1015 (2) 2.25 x 1015 (3) 2.5 x 106 (4) 2.5 x 106

Which of the following graph represents the variation of resistivity (p) with temperature (T) for copper (1) (3) P T T (2) (4) P P T T

Two bodies of mass 4kg and 6kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity (g) is (1) g10 (3) g2 4kg 6kg (2) g (4) g5

A screw gauge has least count of 0.01 mm and there are 50 divisions in its circular scale. The pitch of the screw gauge is (1) 1.0 mm (3) 0.25 mm (2) 0.01 mm (4) 0.5 mm

In Youngs double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes (1) onefourth (2) double (3) half (4) four times

For the logic circuit shown, the truth table is A B (1) (2) (3) (4) A 0 0 1 1 A 0 0 1 1 A 0 0 1 1 A 0 0 1 1 B 0 1 0 1 B 0 1 0 1 B 0 1 0 1 B 0 1 0 1 Y 1 0 0 0 Y 0 0 0 1 Y 0 1 1 1 Y 1 1 1 0 Y

The energy equivalent of 0.5 g of a substance is (1) 0.5 x 103 J (2) 4.5 x 106 J (3) 4.5 x 1013 J (4) 1.5 x 103 J

The quantities of heat required to raise the of two solid copper spheres of radii r and r (r 1.5 r2) through 1 K are in the ratio temperature (1) (3) 53 9 4 (2) (4) 27 8 3 2

When I step out of the shower, what makes the tile floor so much colder than the bathroom mat? Explain in detailed giving examples.

When I bump one end of a long metal bar, the other end instantaneously moves. Can I use this to send messages faster than light? Explain in detailed.

When does a light beam have only a single frequency? Explain in detailed.

What psychological effect makes notes on a piano that are an octave apart sound the same? 30 marks.

What makes radioactive atoms get old so quickly and decay? Explain in detailed giving examples.

Problem 18. A twoport network has parameters A2j, B502, C(1j2)S and D4. If the output is a current of 80mA through a 2012 resistive load, determine (a) the input voltage and (b) the input current.

Problem 25. A symmetricalnetwork has a series impedance of 1060 2 and shunt admittances of 0.01275 S. Determine (a) the transmission matrix and (b) the input voltage and current when there is a load resistance of 2012 across the output and the input voltage produces a current of 1 mA through it.

Determine the cutoff frequency and the nominal impedance of each of the lowpass filter sections shown in Figure 45.19. 100 H m Figure 45.19 (a) 100 DAH (b) 200

The nominal impedance of a lowpass section filter is 500 22 and its cutoff frequency is at 100 kHz. Determine (a) the value of the characteristic impedance of the section at a frequency of 90 kHz and (b) the value of the characteristic impedance of the equivalent lowpass T section filter

A lowpass section filter has a nominal impedance of 600 52 and a cutoff frequency of 2 MHz. Determine the frequency at which the characteristic impedance of the section is (a) 600 12 (b) 1 kf2 (c) 10 km2,

Asymmetricalattenuator pad has a series arm of 500 12 resistance and each shunt arm of 1 k2 resistance. Determine (a) the characteristic impedance and (b) the attenuation (in dB) produced by the pad.

For each of the attenuator networks shown in Figure 44.11, determine (a) the input resistance when the output port is opencircuited, (b) the input resistance when the output port is shortcircuited and (c) the characteristic impedance. 150 Figure 44.11 Dupl ped bod pon 14 50 oupe port

The attenuator shown in Figure 44.18 feeds a matched load. Determine (a) the characteristic impedance Ro and (b) the insertion loss in decibels R 3000 V 4 R 450 Figure 44.18 R 3000 V 42 Ro

strat Under the action of force, 2 kg body moves such that its position as a f 13 of time t is given by x x is in metre and t in second. Calculate the wor 3 by the force in the first 2 second.

What is free body diagram? What are the steps to be followed for developing free body diagram.

The force applied on both the objects is same, but the acceleration experienced by each object differs, Why? Give an example.

Determine the strength of a uniform electric field if it is to have the same energy as that established by a magnetic field of flux density 0.8 T. Assume that the relative permeability of the magnetic field and the relative permittivity of the electric field are both unity.

The current output of an attenuator is 50mA. If the current ratio of the attenuator is 1.32 Np, determine (a) the current input and (b) the current ratio expressed in decibels. Assume that the input and load resistances of the attenuator are equal.

A coaxial cable has an inner core of radius 1.0mm and an outer sheath of internal radius 4.0mm. Determine the inductance of the cable per metre length. Assume that the relative permeability is unity.

A coaxial cable 7.5 km long has a core 10 mm diameter and a sheath 25 mm diameter, the sheath having negligible thickness. Determine for the cable (a) the inductance, assuming nonmagnetic materials, and (b) the capacitance, assuming a dielectric of relative permittivity 3.

A singlephase power line comprises two conductors each with a radius 8.0mm and spaced 1.2 m apart in air. Determine the inductance of the line per metre length ignoring internal linkages. Assume the relative permeability, 1

Determine (a) the loop inductance and (b) the capacitance of a 1 km length of single phase twin line having conductors of diameter 10 mm and spaced 800 mm apart in air.

The total loop inductance of an isolated twin power line is 2.185 Hm. The diameter of each conductor is 12 mm. Determine the distance between their centres.

Calculate the value of the energy stored when a current of 50mA is flowing in a coil of inductance 200 mH. What value of current would double the energy stored

Calculate the Einstein's frequency for a solid of which Einstein's temperature is 236 K. (h=6.610 -34 J s, k= 1.3810 -23 J/K )

The airgap of a moving coil instrument is 2.0mm long and has a crosssectional area of 500 mm. If the flux density is 50mT, determine the total energy stored in the magnetic field of the airgap

Two identical bodies, one of them initially at rest, make elastic oblique collision, show that after collision they will move mutually perpendicular.

Two blocks A and B of mass m and 2m respectively are connected by a spring of force constant k. The masses are moving to the right with uniform velocity v each, the heavier mass, leading the lighter one. The spring is of natural length in the motion. Block B collides head on with a third block C of mass m, at rest, the collision being completely

A concentric cable has a core diameter of 32 mm and an inner sheath diameter of 80 mm. The core potential is 40 kV and the relative permittivity of the dielectric is 3.5. Determine (a) the capacitance per kilometre length of the cable, (b) the dielectric stress at a radius of 30 mm and (c) the maximum and minimum values of dielectric stress.

A singlecore concentric cable is to be manufactured for a 60kV, 50 Hz transmission system. The dielectric used is paper, which has a maximum permissible safe dielectric stress of 10MVm rms. and a relative permittivity of 3.5. Calculate (a) the core and inner sheath radii for the most economical cable, (b) the capacitance per metre length and (c)

Two parallel wires, each of diameter 5 mm, are uniformly spaced in air at a distance of 50 mm between centres. Determine the capacitance of the line if the total length is 200m.

A singlephase circuit is composed of two parallel conductors, each of radius 4 mm, spaced 1.2 m apart in air. The p.d between the conductors at a frequency of 50 Hz is 15 kv. Determine, for a 1 km length of line, (a) the capacitance of the conductors, (b) the value of charge carried by each conductor and (c) the charging current.

The step pulley shown in figure starts from rest and accelerates at 2 rads. What time is required for block A to move 20m Find also the velocity of A and B at that time.

A 400 pF capacitor is charged to a p.d. of 100V. The dielectric has a crosssectional area of 200 cm and a relative permittivity of 2.3. Calculate the energy stored per cubic metre of the dielectric.

Arod PQ of mass m is kept suspended in horizontal position as shown. Linear mass density of rod varies with distance x from its left end P as kx (k is constant). Left string is now cut. Torque about point Qjust after the string is cut is string (a) mg 2 (b) mgl 3 P (c) string mgl 4 (d) mgl 6

A uniform rod of mass m is bent into the form of a semicircle of radius R. Th moment of inertia of the rod about an axis passing through A and perpendicula to the plane of the semicircle is A (a) mR (b) mR R (c) 2mR2 (d) 5 mR

Given a semicircular disc of mass M and radius R. Find its MI about an axis passing through CM and parallel to its diameter.,M 4 R R CM 4R

A uniform rod of length is given an impulse P at a distance x from its CM as shown in figure. The position of the IAOR from the centre of mass is (a) (b) 1 12x (c) 12( (d) 3.x P X

The work function for metal A is 2.74 eV. If metal A is illuminated with light of wavelength 112.4 nm Calculate the maximum kinetic energy (in eV) of the ejected electrons.

In a single atom, how many electrons can be fitted in all the orbitals with principal quantum number n12

The area of a hysteresis loop obtained from a ferromagnetic specimen is 12.5 cm. The scales used were horizontal axis 1 cm500 Am vertical axis 1 cm0.2 T. Determine (a) the hysteresis loss per m per cycle and (b) the hysteresis loss per m at a frequency of 50 Hz

A ferromagnetic ring has a uniform crosssectional area of 2000 mm and a mean circumference of 1000 mm. A hysteresis loop obtained for the specimen is plotted to scales of 10mm0.IT and 10mm400 Am and is found to have an area of 10 mm. Determine the hysteresis loss at a frequency of 80 Hz.

The eddy current loss in a particular magnetic circuit is 10 Wm. If the frequency of operation is reduced from 50 Hz to 30 Hz with the flux density remaining unchanged, determine the new value of eddy current loss per cubic metre.

The core of a transformer operating at 50 Hz has an eddy current loss of 100 Wm and the core laminations have a thickness of 0.50 mm. The core is redesigned so as to operate with the same eddy current loss but at a different voltage and at a frequency of 250 Hz. Assuming that at the new voltage the maximum flux density is onethird of its original

When a transformer is connected to a 500 V, 50 Hz supply, the hysteresis and eddy current losses are 400 W and 150 W, respectively. The applied voltage is increased to 1 kV and the frequency to 100 Hz. Assuming the Steinmetz index to be 1.6, determine the new total core loss.

The total core loss of a ferromagnetic cored transformer winding is measured at different frequencies and the results obtained are Total core loss, P. (watts) 45 105 190 305 Frequency, (hertz) 30 50 70 90 Determine the separate values of the hysteresis and eddy current losses at frequencies of (a) 50 Hz and (b) 60 Hz.

The equivalent series circuit for a particular capacitor consists of a 1.552 resistance in series with a 400 pF capacitor. Determine for the capacitor, at a frequency of 8 MHz, (a) the loss angle, (b) the power factor, (c) the Qfactor and (d) the dissipation factor.

A capacitor has a loss angle of 0.025 rad, and when it is connected across a 5kV, 50 Hz supply, the power loss is 20 W. Determine the component values of the equivalent parallel circuit.

You stand in a flat meadow and observe two cows (Fig. P1.73). Cow A is due north of you and 15.0 m from your position. Cow B is 25.0 m from your position. From your point of view, the angle between cow A and cow B is 20.0, with cow B appearing to the right of cow A. (a) How far apart are cow A and cow B (b) Consider the view seen by cow A.

An a.c. source of 300 V and internal resistance 20 ks2 is matched to a load by a 201 ideal transformer. Determine for maximum power transfer (a) the value of the load resistance and (b) the power dissipated in the load. The network diagram is shown in Figure 38.21. a.c. source 300 V r20 kn Figure 38.21 N R

The values of the voltage v volts at different moments in a cycle are given by e degrees 30 60 90 120 150 180 v (volts) 62 35 38 64 63 52 e degrees 210 240 270 300 330 360 v (volts) 28 24 80 96 90 70 Draw the graph of voltage v against angle and analyse the voltage into its first three constituent harmonics, each coefficient correct to 2 decimal

Without calculating Fourier coefficients state which harmonics will be present in the waveforms shown in Figure 40.4. 400 2 AMA www. f(x) (b) Figure 40,4 2

The Eigen values of a observable associated with a physical quality are 0 and 1. The expectation value of measurement is Zero Either zero or one Between zero and one One

a)300 Hz b)360 Hz c)480 Hz d)420 Hz

A standing wave on a string, with a frequency of 240 Hz. is shown in the top figure panel. In the bottom figure panel, another standing wave on the same string is shown. What is the frequency of this standing wave f 240 Hz An

For the circuit shown in Figure 38.2 the load impedance Z is a pure resistance. Determine (a) the value of R for maximum power to be transferred from the source to the load and (b) the value of the maximum power delivered to R. E1200 V z (15 120) 02 Figure 38.2

If the load impedance Z in Figure 38.2 of Problem 1 consists of variable resistance R and variable reactance X, determine (a) the value of Z that results in maximum power transfer and (b) the value of the maximum power.

In the network shown in Figure 38.4 the load consists of a fixed capacitive reactance of 792 and a variable resistance R. Determine (a) the value of R for which the power transferred to the load is a maximum, and (b) the value of the maximum power. 60.00 Figure 38.4 492 10 (2 0 A 170

Determine, for the network shown in Figure 38.8, (a) the values of R and X that will result in maximum power being transferred across terminals AB and (b) the value of the maximum power. 10030 Figure 38.8 50 100 0

Determine the optimum value of load resistance for maximum power transfer if the load is connected to an amplifier of output resistance 448 2 through a transformer with a turns ratio of 81

A singlephase, 240 V1920 V ideal transformer is supplied from a 240 V source through a cable of resistance 592. If the load across the secondary winding is 1.60 k2, determine (a) the primary current flowing and (b) the power dissipated in the load resistance. The network is shown in Figure 38.20. 240 V R R 50 Figure 38.20 N Load R 1.60 k

A generator has an output impedance of (450j60) 2. Determine the turns ratio of an ideal transformer necessary to match the generator to a load of (40j19) 22 for maximum transfer of power.

Determine the value of the load resistance R shown in Figure 38.5 that gives maximum power dissipation and calculate the value of this power. Figure 38.5 20 v 50 150

a) 3cm b) c) Find the electric field at the origin due to the two point charges if q is 2nC. (8 points) 29 2cm 1q Indicate the force (magnitude and direction) on a 10nC charge placed at the origin. (2 points) If the two original charges are fixed in place and the 10C charge at the origin is placed there at rest, show in which direction it will

The wire in the figure carries a current i and consists of a circular are of radius R and central angle 12 radians, and two straight sections whose extensions intersect the center C of the arc. What magnetic field B (magnitude and direction) does the current produce at C 3 R C (a) 2

For the function below, find (A) f(x). (B) the partition numbers for f, (C) the critical numbers of f. 9 f(x) x7 (A) f(x) 9 (x7) (B) Find the partition numbers for f. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. OA. The partition number(s) isare x OB. There are no partition numbers. (C) Find

Looking toward the Moon with a telescope, you want to be able to see a crater that is 100 km wide. If the distance from the Earth's surface to the Moon's surface is 3.8 108 m, how wide must your telescope aperture diameter be in order to see the edges of the crater clearly? Assume that white light is reflected off the Moon (?avg = 550 nm). A. 2.5

Q28. 5, denotes the spin operator defined S (a) The eigenstates of spin operator S, are (b) The eigenstates of spin operator S, are (c) In the spin state u 1 (d) in the spin state 23 Which one of the following is correct et). (0) and ). and . upon the measurement of S., the probability for obtaining ) is I upon the measurement of S., the

A block with a mass of 10 kg is at rest on a horizontal surface. The coefficient of static friction between the block and the surface p-0.30, and the coefficient of kinetic friction ja -0.25. A force of 20 N acts on the block toward the left. The magnitude of the frictional force on the block is: A) 10 N B) 3.0 N C) 0.10 KN D) 30 N E) 20 N

A block with a mass of 10 kg is at rest on a horizontal surface. The coefficient of static friction between the block and the surface p0.30, and the coefficient of kinetic friction ja 0.25. A force of 20 N acts on the block toward the left. The magnitude of the frictional force on the block is A) 10 N B) 3.0 N C) 0.10 KN D) 30 N E) 20 N