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Physics Questions and Answers September 12, 2022

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Discuss how do levers create energy if the conservation of energy does not allow energy to be created?

Discuss how do free energy machines work? Give detailed answer

Discuss how do airplanes fly upside down if it's the shape of the wings that make them fly?

Discuss how did Archimedes use mirrors to burn up invaders' ships?

Discuss how can radioactive decay just happen with nothing triggering it? Discuss in detailed giving examples.

Discuss how can it be so hard to drag rubber across smooth glass if friction is caused by surface roughness? Give detailed answer with examples.

Explain how bad would a person's injuries be if an elevator's cables snapped at the 100th floor so that the elevator fell to the bottom? Explain in detailed giving exampes.

Does a source of electricity ever run out of electrons?

Explain why will a delivery truck filled with birds sitting on its floor be heavier than a truck with the same birds flying around inside.

Explain why were electrons chosen to be negatively charged? Wouldn't it make more sense to call electrons positively charged because when they move they make electricity?

Explain why is time frozen from light's perspective? Give detailed answer with examples

Discuss why is the lowest temperature called absolute zero if it's relative to the frame of reference?. Give detailed answer with examples.

Explain why is the centrifugal force talked about so much if it's not real?

Discuss why is physics scale invariant? Explain in detailed and give examples.

Discuss why don't scientists use fractal concepts more considering that fractals are everywhere? Discuss in detailed giving examples.

Explain why don't I feel the miles of air above me that are crushing me down?

Explain why don't electrons in the atom enter the nucleus? Explain in detailed giving examples.

Discuss why don't atoms collapse if they are mostly empty space?

Explain why does my room get dark when I turn the lights off even if my window is shut? Explain in detailed.

Discuss why does lightning push electricity through air, but common batteries do not? Explain in detailed giving examples.

Explain why does air friction affect a car's gas mileage? Discuss in detailed giving examples.

Explain why does a rainbow exist only in a narrow band?

Explain why does a rainbow contain a pure spread of spectral colors? Explain in detailed giving examples.

Explain why do quantum effects only happen on the atomic scale?. Explain in detailed giving examples.

Why are there only six fundamental colors: red, orange, yellow, green, blue, and violet? Discuss in detailed giving examples

Explain in detailed why are the microwaves in a microwave oven tuned to water?

Explain why all metals magnetic? Explain in detailed giving examples.

Calculate the breadth B (in degrees of 20), due to the small crystal effect alone, of the powder pattern lines of particles of diameter 1000,750, 500, and 250 . Assume 0 45 and 1.5 . For particles 250 in diameter, calculate the breadth B for 0 10, 45 and 80. Show that the reciprocal of reciprocal lattice gives direct lattice. Show that volume

A 747 jetliner lands and begins to slow to a stop as it moves along the runway. If its mass is 3.50 105 kg, its speed is 27.0 ms, and the net braking force is 4.30105 N, (a) what is its speed 7.50 s later (b) How far has it traveled in this time

0 Tsin T cos 1600 mg,A 0.075kg toy airplane is tied to the ceiling with a string. When the airplanes motor is started, it moves with a constant speed of 1.21 ms in a horizontal circle of radius 0.44 m, as illustrated in Figure 638. Find (a) the angle the string makes with the vertical and (b) the tension in the string.

Consider a flat piece of sheet metal located on the (x, y) plane and rotating about the z axis. Do not take the thickness into account. (a) Which entries of the inertia tensor are equal to zero?(b) Verify that the following relation holds: Izz = Ixx + Iyy. (c) Verify that z is a principal axis. Hint: show that if the angular velocity is aligned

Which of the following units denotes the dimensions MLQ2, where Q denotes the AIEEE 2006 electric charge (a) Wbm (c) Hm (b) henry (H) (d) weber (Wb)

The rad is the correct unit used to report the measurement of AIEEE 2006 (a) the ability of a beam of gamma ray photons to produce ions in a target (b) the energy delivered by radiation to a target (c) the biological effect of radiation (d) the rate of decay of a radioactive source

Out of the following pairs, which one does not have identical dimensions AIEEE 2005 (a) Angular momentum and Plancks constant (b) Impulse and momentum (c) Moment of inertia and moment of a force (d) Work and torque

Which one of the following represents the correct dimensions of the coefficient of AIEEE 2004 viscosity (a) MLT2 (c) MLT (b) MLT (d) MLT

Dimensions of 1oo, where symbols have their usual meaning, are AIEEE 2003 (a) LT (b) LT (b) LT2 (c) LT (d) LT

The physical quantities not having same AIEEE 2003 dimensions are (a) torque and work (b) momentum and Plancks constant (c) stress and Youngs modulus (d) speed and ()2

Identify the pair whose dimensions an equal. AIEEE 200 (a) Torque and work (b) Stress and energy (c) Force and stress (d) Force and work

A circuit and the signal applied at its input terminals (V) are shown in figure below. Which one of the options correctly describes the output waveform (V). (Assume all the devices used are ideal). 2V 0 2V (a) 2v 0 2V (c) 4V 0 HH C V (b) 0 2V (d) 0 4VF D Jo t

In a crystalline solid, the energy band structure (Ek relation) for an electron of mass m k(2k 3) 2m is given by E (a) m 23 The effective mass of the electron in the crystal is (b) m (c) EN m 2 (d) 2m

The truth table for the given circuit is (a) (c) J 0 0 1 1 J 0 0 1 1 K 0 1 0 1 KO 0 1 0 1 K Q 1 0 1 0 Q 0 1 0 1 (b) (d) J 0 0 1 1 J 0 0 1 1 K Q 1 0 0 1 0 1 0 1 K 0 1 0 1 Q 0 1 1 0

In an intrinsic semiconductor, the free carrier concentration n (in cm3) varies with temperature T (in Kelvin) as shown in the figure below. The band gap of the semiconductor is (use Boltzmann constant k 8.62510 eVK) (a) 1.44 eV (b) 0.72 eV (c) 1.38 eV (d) 0.69 eV 36.5 35.5 In(n) 34.5 33.5 32.5 T Fa 2 3 1000T

Fermi energy of a certain metal M, is 5 eV. A second metal M has an electron which is 6 higher than that of M. Assuming that the free electron theory is valid for both the metals, the Fermi energy of M is closet to (a) 5.6 eV (b) 5.2 eV (c) 4.8 eV (d) 4.4 eV

The ratio of the secondneighbour distance to the nearestneighbour distance in an fcc lattice is (a) 22 (b) 2 (c) 3 (d) 2

Consider a doped semiconductor having the electron and the hole mobilities, and , respectively. Its intrinsic carrier density is n. The hole concentration p for which the conductivity is minimum at a given temperature is n Vp (a) n. (b) n. H H (c) n Hp (d) n n Hp P

The logic expression for the output Y of the following circuit is P Q R S (a) PQQR S (c) PQQR S Y 15 (b) PQQR S (d) PQQRS

Monochromatic Xrays of wavelength 1A are incident on a simple cubic crystal. The first order Bragg reflection from (311) plane occurs at angle of 30 from the plane. The 0 lattice parameter of the crystal in A is (a) 1 (b) 3 11 (d) II

Which one of the following is an INCORRECT Boolean expression (a) PQPQQ (b) (PO) (PQ) P (c) P(PQ) Q (d) (POR PORPOR POR) Q

A battery with a constant emf and internal resistance r provides power to an external circuit with a load resistance made up by combining resistance R and 2R, in parallel. For what value of R will the power delivered to the load be maximum (c) R r 2 (a) R 4 (b) R r 2 3 (d) R r 2

The value of at which the firstorder peak in Xray (1.53 ) diffraction corresponding to (111) plane of a simple cubic structure with the lattice constant, a 2.65 A, is approximately (a) 15 (b) 30 (c) 45 (d) 60

Consider the following truth table The logic expression for F is (a) AB BCCA (b) AB AC BC (c) CAB AB (d) C(AB) AB A B C F 0 0 1 0 1 0 1 00 0 0 1 0 0 1 0 0 0 1 0 1 0 1

An Xray diffraction (XRD) experiment is carried out on a crystalline solid having FCC structure at room temperature. The solid undergoes a phase transformation on cooling to 20C and shows orthorhombic structure with small decrease in its unit cell lengths as compared to the FCC unit cell lengths. As a result the (311) line of the XRD G pattern

Which of the following circuit does not satisfy the Boolean expression AB AB F A TO (a) B (c) F A B A (b) B (d) B PD F A D F

An Xray beam of wavelength 1.54 A is diffracted from the (110) planes of a solid with a cubic lattice of lattice constant 3.08 . The firstorder Bragg diffraction occurs at (a) sin (b) sin G 22 (c) sin 9 2 (d) sin

The Boolean expression PPQ, where P and Q are the inputs to a circuit, represents the following logic gate (a) AND (b) NAND (c) NOT (d) OR

The fraction of volume unoccupied in the unit cell of the body centered cubic lattice is 837 3r (a) 627 8 8 6 (b) (c) (d) 32

For an ideal opamp circuit given below, the dc gain and the cut off frequency respectively are (a) 1 and 1kHz (b) 1 and 100 Hz (c) 11 and 1kHz (d) 11 and 100 Hz 1kQ www 1 UF 2 www 1kQ www 10 kQ2

A variable power supply 5V20V is connected to a Zener diode specified by a breakdown voltage of 10V (see figure). The ratio of the maximum power to the minimum power dissipated across the load resistor is 500 92 5V20V www. 1kQ

Octal equivalent of decimal number (478), is (a) 736, (b) 673, (c) 637g (d) 367, 8

In an ideal operational amplifier depicted below, the potential at node A is (a) IV 5 WMA OIV (b) OV www 25 W (c) 5V 5 V (d) 25V

To operate a npn transistor in active region, its emitterbase and collector base junction respectively, should be (a) forward biased and reversed biased (b) forward biased and forward biased (c) reversed biased and forward biased (d) reversed biased and reversed biased

Diamond lattice can be considered as a combination of two fcc lattice displaced along the body diagonal by one quarter of its length. There are eight atoms per unit cell. The packing fraction of the diamond structure is (a) 0.48 (b) 0.74 (c) 0.34 (d) 0.68

in A sine wave of 5V amplitude is applied at the input of the V circuit shown in the figure. Which of the following waveforms represents the output most closely www (a) (c) 5V 5V 3V 3V (b) (d) SV 3V 3V 5V A WWW 1kQ P 3 V out

1011 binary input have been applied at X3XXX, input in the shown logic circuit made of XOR gates. The binary output Y,YYY of the circuit will be Y X3 Y (a) 1101 X0 X Xo (b) 1010 (c) 1111 Y Yo (d) 0101

Temperature dependence of resistivity of a metal can be described by (a) (b) RA (c) RA R4 T T (d) RA T T

Which of the following circuits represent the Boolean expression SPOROP (a) p. Q (c) R D S S (b) p (d) 0 D D R S Do

Miller indicates of a plane in cubic structure that contains all the directions 100, 011 and 111 are (a) (011) (b) (101) (c) (100) (d) (110)

In an ideal OpAmp circuit shown below R 3kQ, R 1kQ and V0.5 sin cot (in Volt). Which of the following statements are true (a) The current through R The current through R (b) The potential at P is Vo R R (c) The amplitude of V, is 2V (d) The output voltage V, is in phase with V 1 P www R www R LoVo

In the given circuit Vcc10V and B100 for npntransistor. The collector voltage Vcc Vc (in volts) is....... fiz 5V 100 K www SIK o Vc

GaAs has a diamond structure. The number of GaAs bonds per atom which have to be broken to fracture the crystal in the (001) plane is..........

The solution of the Boolean equation Y A B AB is (a) 1 (b) AB (c) AB (d) A B

If a constant voltage V is applied to the input of the following OPAMP circuit for a time t, then the output voltage V, will (a) V exponentially (c) V linearly V approach C R ww V (b)V exponentially (d) V linearly

A pn junction was formed with a heavily doped (108 cm ) pregion and lightly doped (104 cm) n region. Which of the following statement (s) is (are) correct (a) The width of the depletion layer will be more in the n side of the junction (b) The width of the depletion layer will be more in the p side of the junction (c) The width of the depletion

The number of secondnearest neighbor ions to a Nation in NaCl crystal is

The output voltage V, of the OPAMP circuit given below is.................V 2R www R 1Vo W R 2V0WW R. 3VoWW OV

In the circuit given below, the collector to emitter voltage V is.. is........ (Neglect VBE, take 100) Vcc 10V 5kQ 35 S 5kQ VCE 10kQ V.

Xray diffraction of a cubic crystal gives an intensity maximum for Bragg angle 20 corresponding to the (110) plane. The lattice parameter of the crystal is.......... nm . (Consider wavelength of Xray 0.15 nm)

Consider the following circuit with two identical Si diodes. The input ac voltage waveform has the peak voltage V 2V, as shown (a) V (c) in 2V The voltage waveform across PQ will be represented by V PO V PQ R www (b) D. Z (d) V PO V PO KIM R D OP

If the Boolean function (a) PQR(STU) (c) PQ ZPQPQRPORSPORSTPQRSTU, then Z is (b) PQ (d) PQRST

Shown in the figure is a combination of logic gates. The output values at P and Q are correctly represented by which of the following 1 (a) 0 0 0 (b) 11 KIS (c) 01 (d) 10

2a A plane in a cubic lattice makes intercepts of a, and 3 crystallographic axes, respectively. The Miller indices for this plane are (a) (243) (b) (342) (c) (634) (d) (123) with the three

Which one of the following schematic curves best represents the variation of conductivity o of a metal with temperature T (a) (c) b 0 T T (b) (d) b T K 0 T

KCl has the NaCl type structure which is fcc with twoatom basis, one at (0,0,0) and the other at (12,12,12). Assume that the atomic form factors of K and Clare identical. In an Xray diffraction experiment on KCl, which of the following (hkl) peaks will be observed (a) (100) (b) (110) (c) (111) (d) (200)

An npn transistor is connected in a circuit as shown in the figure. If Ic1mA, B50,VBE 0.7V and the current through R is 101, where, I, is the base current. Then the ratio RR is (a) 0.375 (b) 0.25 (c) 0.5 (d) 0.275 R R www 6V 2.5k 0.5 k Vc VCE 3V V 0.5V

An intrinsic semiconductor of band gap 1.25 eV has an electron concentration 10 cm at 300 K. Assume that its band gap is independent of temperature and that the electron concentration depends only exponentially on the temperature. If the electron concentration at 200 K is Y10 cm (1

An OPAMP is connected in a circuit with a Zener diode as shown in the figure. The value of resistance R in ko for obtaining a regulated output V9V is. (Specify your answer to two digits after the decimal point) R M 1kQ V 12V in 1kQ2 V 4.7V V.

Which one of the following graphs shows the correct variation of V with V Here, V is the voltage drop across the diode and the OPAmp is assumed to be ideal. VA (a) (c) Vo 0 V V (b) (d) V. D 74 Vo 0 Va Vo 0 V Vo R L

The Boolean expression (AB)(AB)(AB) can be simplified to (a) AB (c) AB (b) AB (d) AB

Which of the combinations of crystal structure and their coordination number is (are) correct (a) body centered cubic 8 (c) diamond 4 (b) face centred cubic 6 (d) hexagonal closed packed12

For the given circuit, value of the base current (I) of the npn transistor will be (B is the current gain and assume OpAmp as ideal.) (Specific your answer in mA upto two digits after the decimal point.) 10V 1k www 5V Ib B 50 1k www. mA.

The lattice constant of unit cell of NaCl crystal is 0.563 nm. Xrays of wavelength 0.141 nm are diffracted by this crystal. The angle at which the first order maximum occurs is degrees.

For the following circuit, the collector voltage with respect to ground will be V. (Emitter diode voltage is 0.7V and Bpc of the transistor is large) (Specify your answer in volts upto one digit after the decimal point). 10V 3k www. 3k 1k 3V

In the following circuit, the time constant RC is much greater than the period of the input signal. Assume diode as ideal and resistance R to be large. The dc output voltage across resistance R will be V. (Specify your answer in volts upto one digit after the decimal point) C 24V rms R

For a metal, the electron density is 6.41028 m3. The Fermi energy is (h6.626x1034 Js, m 9.11103 kg, 1 eV 1.610 J) (Specify your answer in electron volts (eV) upto one digit after the decimal point) eV.

Which one of the following crystallographic planes represent (101) Miller indices of a cubic unit cell (a) ZA (b) ZA x (c) 1. (d) y y

The output of following logic circuit can be simplified to X Y (a) XYZ (b) Y XZ (c) XYZ S (d) XYZ

The location of Cs and CI ions inside the unit cell of cacl crystal is shown in the figure. The Bravais lattice of CaCl is az (a) Simple cubic (c) Face centred cubic a OCT Cs (b) Body centred orthorhomble (d) Base centred orthorhombic

In the Xray diffraction pattern recorded for a simple cubic solid (lattice) parameter a1) using Xrays of wavelength 1, the first order diffraction peak(s) would appear for the (a) (100) planes (b) (112) planes (c) (210) planes (d) (220) planes

Sodium (Na) exhibits bodycentred cubic (BCC) crystal structure with atomic radius 0.186 nm. The lattice parameter of Na unit cell is nm.

For the input voltage V (200 mV) sin (400t), the amplitude of the output voltage (V) of the given OPAMP circuit is V. (Round off to 2 decimal places) 10kQ2 R 35 R 10 IM R 35 R 10k R 35 ww R Vo