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Physics Questions and Answers September 24, 2022

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During polarization experiment, the plane of polarization is rotated using Half Wave Plate (HWP) if initially, light is perpendicularly polarized. Explain the procedure with respect to output intensity and state of polarization. (25) If Malf wave plate is replaced with Quarter Wave Plate (QWP) then find the output intensity and state of

In the experiment of spectrometer to find the wavelength of polychromatic source using grating, first find how to place grating normal to the collimator. (25) Table 2 Reading for angle of grating diffraction Position V V MSR VSC Total MSR VSC 381 5 Left side reading 301 29 Right side reading Using the above data to identify the specific wavelength

Which one of the following is similar between electrostatic force and gravitational force a) Force can be attractive or repulsive b) The force depends on the medium between the bodies c) Both the forces are strong forces d) Force is inversely proportional to the distance between the bodies

Two charges q1, q2 exert some amount of force on each other. What will happen to the force on q if another charge q3 is brought close to them a) The force will increase b) The force will decrease c) The force remains the same d) The force may increase or decrease depending on whether q3 is positive or negative

Three equal positive charges are kept at the corners of an equilateral triangle. What will be the vector sum of the forces acting on the particles? a) Directed towards the center b) Directed radially outside c) Acts along one of the sides of the triangle d) Zero

Which among the following is false? a) Coulomb force is a central force b) The force between two charges depend on the medium between them c) Coulomb force is a weak force d) The net force on a charge is the vector sum of the forces acting on it due to several other charges

A rod of length 2 cm makes an angle 3 principal axis of a thin convex lens. The lens has a focal length of 10 cm and is placed at a distance of 40 cm from the object as shown in the figure, The 3 rad with the height of the image is 303 and the angle made by it 13 with respect to the principal axis is a rad. The value of a is rad, where n is n 3 2

In the following circuit C 12 F, C C3 4 F and C4 C5 2 uF. The charge stored in C3 is C. 6V C C C3 C4 C5 2 J
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The minimum kinetic energy needed by an alpha particle to cause the nuclear reaction N He H O in a laboratory frame is n (in MeV). Assume that N is at rest in the 16 laboratory frame. The masses of N, He, H and O N, He, H and O can be taken to be 16.006 u, 4.003 u, 1.008 u and 19.003 u, respectively, where 1 u 930 MeVc2. The value of n is

Two spherical stars A and B have densities PA and PB, respectively. A and B have the same radius, and their masses M and M are related by MB 2 MA. Due to an interaction process, star A loses some of its mass, so that its radius is halved, while its spherical shape is retained, and its density remains PA. The entire mass lost by A is deposited as

An ideal gas of density p 0.2 kg m enters a chimney of height h at the rate of a 0.8 kg s from its lower end, and escapes through the upper end as shown in the figure. The crosssectional area of the lower end is A 0.1 m and the upper end is A 0.4 m. The pressure and the temperature of the gas at the lower end are 600 Pa and 300 K, respectively,

A medium having dielectric constant K 1 fills the space between the plates of a parallel plate capacitor. The plates have large area, and the distance between them is d. The capacitor is connected to a battery of,voltage V, as shown in Figure (a). Now, both the plates are moved by a distance d2 of from their original positions, as shown in Figure

A projectile is fired from horizontal ground with speed v and projection angle 0. When the acceleration due to gravity is g, the range of the projectile is d. If at the highest point in its trajectory, the projectile enters a different region where the effective acceleration due to gravity is g The value of n is g 0.81 then the new range is dnd.

Consider an LC circuit, with inductance L0.1 H and capacitance C 10F, kept on a plane. The area of the circuit is 1 m. It is placed in a constant magnetic field of strength Bo which is perpendicular to the plane of the circuit. At time t 0, the magnetic field strength starts increasing linearly as BB t with B0.04Ts. The maximum magnitude of the
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A solid sphere of mass 1 kg and radius 1 m rolls without slipping on a fixed inclined plane with an angle of inclination 030 from the horizontal. Two forces of magnitude 1N each, parallel to the incline, act on the sphere, both at distance r 0.5 m from the center of the sphere, as shown in the figure. The acceleration of the sphere down the plane

At time t0, a disk of radius 1 m starts to roll without slipping on a horizontal plane with an angular 2 acceleration of rad s. A small stone is stuck to the disk. At t 0, it is at the contact point of the 3 disk and the plane. Later, at time t s, the stone detaches itself and flies off tangentially from the disk. 1 X . 2 10 The value of
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Six charges are placed around a regular hexagon of side length a as shown in the figure. Five of them have charge q, and the remaining one has charge x . The perpendicular from each charge to the nearest hexagon side passes through the center O of the hexagon and is bisected by the side. JO q O H q 90 X a 9 Which of the following statement(s)

Three plane mirrors form an equilateral triangle with each side of length L. There is a small hole at a distance 0 from one of the corners as shown in the figure. A ray of light is passed through the hole at an angle 0 and can only come out through the same hole. The cross section of the mirror configuration and the ray of light lie on the same

Investigate the properties of the polynomial equation f(x) x 5x6 x4 x x 2 0, by proceeding as follows. (a) By writing the fifthdegree polynomial appearing in the expression for f(x) in the form 7x5 30x4 a(x b) c, show that there is in fact only one positive root of f(x) 0. (b) By evaluating f(1), f(0) and f(1), and by inspecting the

Describe working principle of heterojunction semiconductor laser.

The past 18 weekly sales (y,) for a product are given in the following table. Week Sales Week Sales 1 98 10 170 200 190 220 210 2345 6 7 8 9 100 110 150 140 160 200 150 156 12 13 14 15 16 17 18 260 258 270 240 Assume that the model applicable to these data is given by the equation y, Bo Bt , where t indicates time (here week) with t 1, 2, . .

A cars bumper is designed to withstand a 4.0kmh (1.1ms) collision with an immovable object without damage to the body of the car. The bumper cushions the shock by absorbing the force over a distance. Calculate the magnitude of the average force on a bumper that collapses 0.200 m while bringing a 900kg car to rest from an initial speed of 1.1 ms.

Find the radii of convergence of the following Taylor series 00 nlz )a( DO In n (b) (c) )znn, (d) n1 n1 (z) n1 z, with p real.

Find an analytic function of z xiy whose imaginary part is (y cos y x sin y) exp x.

Consider this diagram in which ethyl acetate is contained in a container with a piston If the system is maintained at 50C describe what happens inside the cylinder when the piston is withdrawn Be brief.

Qualitatively indicate how attractive intermolecular forces are related to a) Hvap.m b) boiling point vapour pressure Also, show an example, like mercury vs water

Consider a stone of irregular shape. Which property of the stone can be found by lowering it into a measuring cylinder halffilled with water A length B mass C volume D weight

On Mars, the acceleration of free fall g is 3.7 ms. What is the weight of a 2.0 kg mass on Mars A 0.54 N B 1.9 N C 7.4 N D 20 N

The mass of an empty flask is 34 g. The volume of liquid added to the flask is 20 cm. The total mass of the flask and the liquid is 50 g. What is the density of the liquid A. 0.80 gcm B. 1.25 gcm C. 2.50 gcm D. 4.20 gcm

The diagram shows a solid object on a flat surface, with two forces acting on the object. 3N 4N What is the resultant force on the object A 1 N to the left BIN to the right C 7 N to the left D 7 N to the right

Find the equivalent resistance for the circuit shown in Figure 7.20. R1 R 2.2 Figure 7.20 R3 30 R 60 R 18 R6 40

A parallel plate capacitor has 19 interleaved plates each 75 mm by 75 mm separated by mica sheets 0.2 mm thick. Assuming the relative of the mica is 5, calculate the of the capacitor. permittivity capacitance

Capacitances of 1 F, 3 F, 5F and 6 F are connected in parallel to a direct voltage supply of 100 V. Determine (a) the equivalent circuit capacitance, (b) the total charge and (c) the charge on each capacitor.

Resolve 23x2 fractions. into partial

A singlephase 500V100 V, 50 Hz transformer has a maximum core flux density of 1.5T and an effective core crosssectional area of 50 cm. Determine the number of primary and secondary turns.

A 4500 V225 V, 50 Hz singlephase transformer is to have an approximate e m.f.per turn of 15 V and operate with a maximum flux density of 1.4 T. Calculate (a) the number of primary and secondary turns and (b) the crosssectional area of the core.

A 5kVA, 200 V400 V, singlephase transformer has a secondary terminal voltage of 387.6 volts when loaded. Determine the regulation of the transformer.

The opencircuit voltage of a transformer is 240 V. A tapchanging device is set to operate when the percentage regulation drops below 2.5. Determine the load voltage at which the mechanism operates. (no load voltan

A 200 kVA rated transformer has a fullload copper loss of 1.5 kW and an iron loss of 1 kW. Determine the transformer efficiency at full load and 0.85 power factor.

Determine the efficiency of the transformer in worked Problem 16 at half full load and 0.85 power factor.

A singlephase auto transformer has a voltage ratio 320 V 250 V and supplies a load of 20kVA at 250V. Assuming an ideal transformer, determine the current in each section of the winding.

Determine the saving in the volume of copper used in an auto transformer compared with a doublewound transformer for (a) a 200 V150 V transformer, and (b) a 500 V100 V transformer.

A current transformer has a single turn on the primary winding and a secondary winding of 60 turns. The secondary winding is connected to an ammeter with a resistance of 0.152. The resistance of the secondary winding is 0.25 12. If the current in the primary winding is 300 A, determine (a) the reading on the ammeter, (b) the potential difference

A steady voltage of 0.75 V is applied to an op amp integrator having component values of R200 ks and C2.5 F. Assuming that the initial capacitor charge is zero, determine the value of the output voltage 100 ms after application of the input.

In the differential amplifier shown in Figure 20.17, R 10k2, R 10ks, R3 100 ks2 and Ry100kn. Determine the output voltage V, if (a) V5 mV and V0 (b) V0 and V5mV (c) V50mV and V25 mV (d) V 25 mV and V50mV

Three 1212 resistors are connected in star to a 415 V, threephase supply. Determine the total power dissipated by the resistors. Be

A 415 V threephase a.c. motor has a power output of 12.75 kW and operates at a power factor of 0.77 lagging and with an efficiency of 85. If the motor is deltaconnected, determine (a) the power input, (b) the line current and (c) the phase current.

Two wattmeters are connected to measure the input power to a balanced threephase load by the twowattmeter method. If the instrument readings are 8 kW and 4 kW, determine (a) the total power input and (b) the load power factor.

Two wattmeters indicate 10kW and 3kW, respectively, when connected to measure the input power to a threephase balanced load, the reverse switch being operated on the meter indicating the 3 kW reading. Determine (a) the input power and (b) the load power factor

An ideal transformer has a turns ra of 81 and the primary current is 3 A when it is supplied at 240 V. Calculate the secondary voltag and current.

A transformer takes a current of 0.8 when its primary is connected to a 240 volt, 50 Hz supply, the secondary being on open circuit. If the power absorbed is 72 watts, determine (a) the iron loss current, (b) the power factor on noload and (c) the magnetizing current.

The winding of an electromagnet has an inductance of 3 H and a resistance of 15 2. When it is connected to a 120 V d.c. supply, calculate (a) the steady state value of current flowing in the winding. (b) the time constant of the circuit, (d) (e) the value of the induced e.m.f. after 0.1s, the time for the current to rise to 85 of its final value

The field winding of a 110V d.c. motor has a resistance of 15 22 and a time constant of 2s. Determine the inductance and use the tangential method to draw the currenttime characteristic when the supply is removed and replaced by a shorting link. From the characteristic, determine (a) the current flowing in the winding 3s after being shortedout and

A coil having an inductance of 6 H and a resistance of R 2 is connected in series with a resistor of 102 to a 120V d.c. supply. The time constant of the circuit is 300 ms. When steady state conditions have been reached, the supply is replaced instantaneously by a shortcircuit. Determine (a) the resistance of the coil, (b) the current flowing in

An inductor has a negligible resistance and an inductance of 200 mH and is connected in series with a 1 k2 resistor to a 24 V d.c. supply. Determine the time constant of the circuit and the steady state value of the current flowing in the circuit. Find (a) the current flowing in the circuit at a time equal to one time constant, (b) the voltage

Determine the commonmode gain of an op amp that has a differential voltage gain of 150 x 10 and a CMRR of 90 dB.

A differential amplifier has an openloop voltage gain of 120 and a common input signal of 3.0 V to both terminals. An output signal of 24 mV results. Calculate the commonmode gain and the CMRR.

The op amp shown in Figure 20.6 has an input bias current of 100 nA at 20C. Calculate (a) the voltage gain, and (b) the output offset voltage due to the input bias current. (c) How can the effect of input bias current be minimized

For the op amp shown in Figure 20.9, R 4.7k2 and R10k52. If the input voltage is 0.4 V, determine (a) the voltage gain (b) the output voltage. Input voltage Figure 20.9 R R Output voltage OOV

For the summing op amp shown in Figure 20.12, determine the output voltage, Vo 0.5Vo 0.8Vo 1.2V o 10k 20k 30k 777 50k

Devise a lightoperated alarm circuit using an op amp, an LDR, an LED and a 15V supply.

A coil of inductance 0.20 H and resistance 602 is connected in parallel with a 20 F capacitor across a 20 V, variable frequency supply. Calculate (a) the resonant frequency, (b) the dynamic resistance, (c) the current at resonance and (d) the circuit Qfactor at resonance.

A coil of inductance 100 mH and resistance 800 2 is connected in parallel with a variable capacitor across a 12 V, 5 kHz supply. Determine for the condition when the supply current is a minimum (a) the capacitance of the capacitor, (b) the dynamic resistance, (c) the supply current and (d) the Qfactor.

In the circuit of Figure 18.16, what value of capacitor is needed to improve the power factor from 0.6 lagging to unity IM50AA Figure 18.16 IA lc M C V240 V, 50 Hz

An inductive load takes a current of 60 A at a power factor of 0.643 lagging when connected to a 240 V, 60 Hz supply. It is required to improve the power factor to 0.80 lagging by connecting a capacitor in parallel with the load. Calculate (a) the new supply current, (b) the capacitor current and (c) the value of the power factor correction

A motor has an output of 4.8 kW, an efficiency of 80 and a power factor of 0.625 lagging when operated from a 240 V, 50 Hz supply. It is required to improve the power factor to 0.95 lagging by connecting a capacitor in parallel with the motor. Determine (a) the current taken by the motor, (b) the supply current after power factor correction, (c)

A 250 V, 50 Hz singlephase supply feeds the following loads (i) incandescent lamps taking a current of 10A at unity power factor, (ii) fluorescent lamps taking 8 A at a power factor of 0.7 lagging, (iii) a 3 kVA motor operating at full load and at a power factor of 0.8 lagging and (iv) a static capacitor. Determine, for the lamps and motor, (a)

A circuit consists of a resistor connected in series with a 0.5 F capacitor and has a time constant of 12ms. Determine (a) the value of the resistor, and (b) the capacitor voltage 7 ms after connecting the circuit to a 10 V supply.

A circuit consists of a 10F capacitor connected in series with a 25 k2 resistor with a switchable 100V d.c. supply. When the supply is connected, calculate (a) the time constant, (b) the maximum current, (c) the voltage across the capacitor after 0.5s, (d) the current flowing after one time constant, (e) the voltage across the resistor after 0.1

A 0.1 F capacitor is charged to 200 V before being connected across a 4 ks2 resistor. Determine (a) the initial discharge current, (b) the time constant of the circuit and (c) the minimum time required for the voltage across the capacitor to fall to less than 2 V.

A coil of inductance 0.04 H and resistance 102 is connected to a 120 V d.c. supply. Determine (a) the final value of current, (b) the time constant of the circuit, (c) the value of current after time equal to the time constant from the instant the supply voltage is connected, and (d) the expected time for the current to rise to within 1 of its

A coil of negligible resistance and inductance 100 mH is connected in series with a capacitance of 2 F and a resistance of 102 across a 50 V, variable frequency supply. Determine (a) the resonant frequency, (b) the current at resonance, (c) the voltages across the coil and the capacitor at resonance and (d) the Qfactor of the circuit.

A series circuit of resistance 60 and inductance 75 mH is connected to a 110V, 60 Hz supply. Calculate the power dissipated.

A circuit consisting of a resistor in series with a capacitor takes 100 watts at a power factor of 0.5 from a 100 V, 60 Hz supply. Find (a) the current flowing, (b) the phase angle, (c) the resistance, (d) the impedance and (e) the capacitance.

A 2012 resistor is connected in parallel with an inductance of 2.387 mH across a 60 V, 1 kHz supply. Calculate (a) the current in each branch, (b) the supply current, (c) the circuit phase angle, (d) the circuit impedance, and (e) the power consumed.

A 30F capacitor is connected in parallel with an 80 2 resistor across a 240 V, 50 Hz supply. Calculate (a) the current in each branch, (b) the supply current, (c) the circuit phase angle, (d) the circuit impedance, (e) the power dissipated and (f) the apparent power.

A capacitor C is connected in parallel with a resistor R across a 120 V, 200 Hz supply. The supply current is 2 A at a power factor of 0.6 leading. Determine the values of C and R.

A pure inductance of 150 mH is connected in parallel with a 40F capacitor across a 50 V, variable frequency supply. Determine (a) the resonant frequency of the circuit and (b) the current circulating in the capacitor and inductance at resonance.

A capacitor C is connected in series with a 4022 resistor across a supply of frequency 60 Hz. A current of 3 A flows and the circuit impedance is 50 2. Calculate (a) the value of capacitance, C, (b) the supply voltage, (c) the phase angle between the supply voltage and current, (d) the p.d. across the resistor and (e) the p.d. across the

A coil of resistance 52 and inductance 120 mH in series with a 100F capacitor is connected to a 300 V, 50 Hz supply. Calculate (a) the current flowing, (b) the phase difference between the supply voltage and current, (c) the voltage across the coil and (d) the voltage across the capacitor.

Analyze the following circuit using LKV B) Change the NPN transistor to an PNP (so the 2 transistors are PNP) reanalize the circuit C) After the 2 analysis Explain what does this circuit do,330K B NPN AK IK m E PNP 10u E LED 22.0 3V

In the US, the allocation of vaccines follows a public-private partnership, where government purchases account for more than 50% of the vaccine market (NCBI, 2003). 1) Would the market price alone work as a good allocation method for vaccines in the U.S.? Yes/No 2) From the list of methods of allocations, mention two used in the U.S. to allocate

An ideal monatomic gas expands quasistatically to twice its volume. If the process is isothermal, the work done by the gas is W. If the process is adiabatic, the work done by the gas is Wa. Which is the following is true A. W Wa B. o Wi Wa C. o W Wa D. o Wa

A threedimensional harmonic oscillator is in thermal equilibrium with a temperature reservoir at temperature T. The average total energy of oscillator is A. 12kT B. KT C. 32kT D. 3kT E. 6kT

In a non relativistic, onedimensional collision, a particle of mass 2m collides with a particle of mass m at rest. If the particles stick together after the collision, what fraction of the initial kinetic energy is lost in the collision A. o B. 14 C. 13 D. 12 E. 23

Five positive charges of magnitude q are arranged symmetrically around the circumference of a circle of radius r. What is the magnitude of the electric field at the center of the circle (k 147E) A. o B. kqr C. 5kg1 D. (kqr) cos (275) E. (5kqr) cos (275)

A positive charge Q is located at a distance L above an infinite grounded conducting plane, as shown in the figure above. What is the total charge induced on the plane A. 2Q B. Q C. O D. Q E. 2Q

Electromagnetism Magnetic Field N N Two long identical bar magnets are placed under a horizontal piece of paper, as shown in the figure above. The paper is covered with iron fillings. When the two north poles are a small distance apart and touching the paper, the iron filings move into pattern that shows the magnetic field lines. Which is the

Four Springs are Connected in series Connection which have Spring constants respectively 30 Nm, go Nm What will be the effective Spring Constant Find the effective Spring Constant when these arre 50 Nm 70 Nm 1 1 connected in parallel Connection.

A student makes 10 onesecond measurement of the disintegration of a sample of a long lived radioactive isotope and obtains a following values 3, 0, 2, 1, 2, 4, 0, 1, 2, 5. How long should the student count to establish the rate to an uncertainty of 1 percent A. 80 s B. 160 s C. 2000 S D. 5000 s E. 6400 s

Five classes of students measure the height of a building. Each classes uses a different method and each measures the height many different times. The data for each class are plotted below. Which class made the most precise measurement (A) (B) 0 (D) (E) Number of Trials Number of Trials Number of Trials Number of Trials Number of Trials 30 20 10

An 8cm diameter by 8cm long NAI(TI) detector detects gamma rays of a specific energy from a point source of radioactivity. When the source is placed just next to the detector at the center of the circular face, 50 percents of all emitted gamma rays at that energy are detected. If the detector is moved to 1 meter away, the fraction of detected

A spherical concave mirror is shown in the figure above. The focal point F and the location of the object O are indicated. At what point will the image be located A. I B. II C. III FO INV D. IV E. V

A particle is initially at rest at the top of a curved frictionless track. The x and ycoordinate of the track are related in dimensionless units by y x4, where the positive yaxis is in the vertical downward direction. As the particle slides down the track, what its tangential acceleration A. o B. g C. gx2 Track D. gx(x4) E. (gx2)(x16)

Two small spheres of putty, A and B of mass M and 3M, respectively, hang from the ceiling on strings of equal length 1. Sphere A is drawn aside so that it is raised to a height ho as shown above and then released. Sphere A collides with sphere B they stick together and swing to a maximum height h equal to A. (116) ho B. (18) ho C. (14) ho D. (13)

The equation y Asin 2, G constants, represents a wave whose T where A, T, and are positive A. Amplitude is 24 B. Velocity is in the negative xdirection C. Period is TX D. Speed is xt E. Speed is T

For blue light, a transparent material has a relative permittivity (dielectric constant) of 2.1 and a relative permeability of 1.0. If the speed of light in vacuum is e, the phase velocity of blue light in an unbounded medium of this material is A. 3.1 c B. 2.1 c C. cV1.1 D. cV2.1 E. c3.1

A Satellite orbits the Earth in a circular orbit. An Astronaut on board perturbs the orbit slightly by briefly firing a control jet aimed toward the Earths center. Afterward, which of the following is true of the satellites path A. It is an ellipse B. It is a hyperbola C. It is a circle with larger radius D. It is a spiral with increasing radius

A rock is thrown vertically upward with initial speed vo. Assume a friction force proportional to v, where u is the velocity of the rock, and neglect the buoyant force exerted by air. Which of the following is correct A. The acceleration of the rock is always equal to g. B. The acceleration of the rock is equal to g only at the top of the flight.

In the production of Xrays, the term bremsstrahlung refers to which of the following A. The cutoff wavelength, Amin, of the Xray tube B. The discrete Xray lines emitted when an electron in an outer orbit fills a vacancy in an inner orbit of the atoms in the target metal of the Xray tube C. The discrete Xray lines absorbed when an electron in an