General Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ

General Physics Quiz | objective questions | Physics General Knowledge Questions | MCQ

1 >>Four solid spheres each of diameter 5^1/2 cm and mass 0.5 kg are placed with their centers at the corners of a square of side 4cm. The moment of inertia of the system about the diagonal of the square is N x 10-4 kg -m² , then N is ?

• (A) 9
• (B) 8
• (C) 7
• (D) 6

Solution a

2 >>A long circular tube of length 10 m and radius 0.3 m carries a current I along its curved surface as shown. A wire-loop of resistance 0.005 ohm and of radius 0.1 m is placed inside the tube with its axis coinciding with the axis of the tube. The current varies as I = I_o cos(300 t) where I_o is constant. If the magnetic moment of the loop is Nu_oI_o sin 300t , then ’N’ is ?

• (A) 6
• (B) 7
• (C) 8
• (D) 9

Solution I = (4*2*MR2/5) + Ma2/2 =>N11*10-4 => N=9

3 >>Four point charges, each of +q, are rigidly fixed at the four corners of a square planar soap film of side ’ α ’. The surface tension of the soap film is γ . The system of charges and planar film are in equilibrium, the a =(q² /(γ))^1/N ,where ’˜k’ is a constant. Then N is ?

• (A) 3
• (B) 4
• (C) 5
• (D) 6

Solution ni=I/l => B=uo Io cos(300 t)/l => V = dB/dt => i= V/R => m = i /π R2

4 >>Radiocarbon is produced in the atmosphere as a result of ?

• (A) collision between fast neutrons and nitrogen nuclei present in the atmosphere
• (B) action of ultraviolet light from the sun on atmospheric oxygen
• (C) action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere
• (D) lightning discharge in atmosphere

Solution

5 >>It is easier to roll a stone up a sloping road than to lift it vertical upwards because ?

• (A) work done in rolling is more than in lifting
• (B) work done in lifting the stone is equal to rolling it
• (C) work done in both is same but the rate of doing work is less in rolling
• (D) work done in rolling a stone is less than in lifting it

Solution Fast moving neutron have a sufficient energy to penetrate the nitrogen nucleus and absorbedby it. Hence it make a intermdiate unstable element finallyit gives carbon-14 and a electron.

6 >>The absorption of ink by blotting paper involves ?

• (A) viscosity of ink
• (B) capillary action phenomenon
• (C) diffusion of ink through the blotting
• (D) siphon action

Solution Work done in rolling is less than lifting due to a extra work has been done in lifting due to gravity means against the gravity but in rolling on a inclined plane we get a work done by gravity in downward direction along the gravity.

7 >>Siphon will fail to work if ?

• (A) the densities of the liquid in the two vessels are equal
• (B) the level of the liquid in the two vessels are at the same height
• (C) both its limbs are of unequal length
• (D) the temperature of the liquids in the two vessels are the same

Solution Blotting paper provide a capillary tube for ink so ink fill in capillary tube and absorbed by blotting paper continuously.

8 >>Large transformers, when used for some time, become very hot and are cooled by circulating oil. The heating of the transformer is due to ?

• (A) the heating effect of current alone
• (B) hysteresis loss alone
• (C) both the heating effect of current and hysteresis loss
• (D) intense sunlight at noon

Solution Both the vessel has a liquid has a same heigt then the liquid are of the same desity, then work done will be zero.

9 >>Nuclear sizes are expressed in a unit named ?

• (A) Fermi
• (B) angstrom
• (C) newton
• (D) tesla

Solution In alternating current a power dissipation due to heating effect p=i2R so heat is produce and eddy current produce in transformer also and they absorbed by circulating oil so heat produce due to both phenomenon.

10 >>Light year is a unit of ?

• (A) time
• (B) distance
• (C) light
• (D) intensity of light

Solution Fermi - A unit of length equal to 10-15 meter (one femtometer), used in nuclear physics. It is similar to the diameter of a proton.

11 >>Mirage is due to ?

• (A) unequal heating of different parts of the atmosphere
• (B) magnetic disturbances in the atmosphere
• (C) depletion of ozone layer in the atmosphere
• (D) equal heating of different parts of the atmosphere

Solution 1 light year is equal to 9460730472580.8 km.

12 >>Light from the Sun reaches us in nearly ?

• (A) 2 minutes
• (B) 4 minutes
• (C) 8 minutes
• (D) 16 minutes

Solution The Above Phenomenon is a great example of TOTAL INTERNAL REFLACTION, Which comes in account when light travels from denser medium to rearer medium, after some specific angle it again reflacts into the denser medium. Similar kind of activity happens in desert area called Mirage or Marichica.

13 >>Stars appears to move from east to west because ?

• (A) all stars move from east to west
• (B) the earth rotates from west to east
• (C) the earth rotates from east to west
• (D) the background of the stars moves from west to east

Solution Speed of light = 3x108 m/s. Distance between the earth & the Sun is = 150000000 KM. So the time taken by light to cover this. Distance is = 150000000000 m/3x1108 m/s => 500 sec. /60 => 8 min. 20 sec.

14 >>Pa(Pascal) is the unit for ?

• (A) thrust
• (B) pressure
• (C) frequency
• (D) conductivity

Solution Earth revolve around the sun in anticlockwise direction and rotate about an its axis so the motion of earth is west to east with respect to star so according to the theorem of relativity we assume that star is moving east to west whenever the star is static with respect to earth and no one atmoshphere is moving.

15 >>Planets do not twinkle because ?

• (A) they emit light of a constant intensity
• (B) their distance from the earth does not change with time
• (C) they are very far away from the earth resulting in decrease in intensity of light
• (D) they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable

Solution This unit was discovered by Pascal so unit of pressure is Pascal.

16 >>Metals are good conductors of electricity because ?

• (A) they contain free electrons
• (B) the atoms are lightly packed
• (C) they have high melting point
• (D) All of these

Solution A star has its own light (Our SUN also one of the star). But a planet has no light of its own. It shines by reflecting the light of the sun.

17 >>Let a thin capillary tube be replaced with another tube of insufficient length then, we find water ?

• (A) will overflow
• (B) will not rise
• (C) depressed
• (D) change its meniscus

Solution Conductors have free electrons in valence band. There is no forbidden energy gap between valence band and conduction band. Thus the electrons can readily jump from valence band to conduction band. Thus motion of electrons implies flow of current and hence metals are good conductors.

18 >>Out of the following pairs, choose the pair in which the physical quantities do not have identical dimension? ?

• (A) Pressure and Young's modules
• (B) Planck's constant and Angular momentum
• (C) Impulse and moment of force
• (D) Force and rate of change of linear momentum

Solution Since in capillary tube liquid flows against the gravity where the liquid continuosly rises in the narrow space but it is not so in any other tube of insufficient lenth.

19 >>If two bodies of different masses, initially at rest, are acted upon by the same force for the same time, then the both bodies acquire the same ?

• (A) velocity
• (B) momentum
• (C) accelaration
• (D) kinetic energy

Solution Impulse means change in the momentum of a body i.e. Impulse = Ft = mv - mu The turning effect of force about the axis of rotation is called moment of force or torque. So they don't have any units... resulting no dimensions!!

20 >>Pick out the scalar quantity ?

• (A) force
• (B) pressure
• (C) velocity
• (D) accelaration

Solution 1)According to newton,s 2nd law force = rate of change of momentum i.e.,momentum=m*v F= M*(D*V/DT)=M*A so it is case of m1v1 and m2v2 m1 is not = m2 hence v1 is not = v2 now Newton's 3rd law come in pictutre during impact F1=F2 ......(equal and opposite reaction) hence m1a1=m2a2 momentum1=momentum2 2)it can be a case of special relativity increase in velocity= increase in inertia = increase in enrgy then apply law of conservation of energy again newtons 3rd law 3)concider it is case of closed system between two bodies

21 >>The wavelength of the first spectral line in the Balmer series of hydrogen atom is 6561 A^o,The wavelength of the second spectral line in the Balmer series of singly-ionized helium
atom is ?

• (A) 1215A^o
• (B) 1640A^o
• (C) 2430A^o
• (D) 4687A^o

Solution (1/(λ1)= (1)2((1/(22))-(1/(32))) =>(1/(λ2)= (2)2((1/(22))-(1/(42))) =>(λ2)/(λ1)=(5*4*16)/(4*4*9*12)= 5/27 =>(λ2) = (6561*5)/27 = 1215A o

22 >>A ball of mass (m) 0.5 kg is attached to the end of a string having length (L) 0.5 m. The ball is
rotated on a horizontal circular path about vertical axis. The maximum tension that the string
can bear is 324 N. The maximum possible value of angular velocity of ball (in radian/s) is ?

• (A) 9
• (B) 18
• (C) 27
• (D) 36

Solution 324=( 1/2)*( 1 /2)*w2 w = 2*18 => w= 36

23 >>A meter bridge is set-up as shown, to determine an unknown resistance ’X’ using a standard
10 ohm resistor. The galvanometer shows null point when tapping - key is at 52 cm mark.
The end-corrections are 1 cm and 2cm respectively for the ends A and B. The determined
value of ’X’ is ?

• (A) 10.2 ohm
• (B) 10.6 ohm
• (C) 10.8 ohm
• (D) 11.1 ohm

Solution Y/(52 + 1) = 10/(48 + 2) X = 10 x (53/50) X =10.6ohm

24 >>A 2uF capacitor is charged as shown in figure. The percentage of its stored energy dissipated
after the switch S is turned to position 2 is ?

• (A) 0
• (B) 0.2
• (C) 0.75
• (D) 0.8

Solution q0= 2V =>(q1)/2 = (q2)/8 =>4q1 = q2 =>q1 + q2 = 2V =>5q1 = 2V =>q1 = (2/5) V =>q2 = (8/5)V => 4*(V2)/4 = ((4*(V2))/(25*4) +(64 *(V2))/(25*2*8) =>4(V2) = 4*(V2)/25 + 16*(V2)/25 =>4(V2) = 1 - (1/2) -(4/25) =>4(V2) = (25-1-4)/25 =(20/25) *100 = 80

25 >>A police car with a siren of frequency 8kHz is moving with uniform velocity 36km/hr towards
a tall building which reflects the sound waves. The speed of sound in air is 320 m/s. The
frequency of the siren heard by the car driver is ?

• (A) 8.50 kHz
• (B) 8.250 kHz
• (C) 7.750 kHz
• (D) 7.50 kHz

Solution frequency reflected by wall f’ f’ = 8 *103[ 320/(320 - 10)] frequency heared by car driver f″= [(320 + 10)/320]f’ f″ = 8* 103 (32/31) *(33/32) =8.50 kHz

26 >>5.6 liter of helium gas at STP is adiabatically compressed to 0.7 liter. Taking the initial temperature to be T¹ , the work done in the process is ?

• (A) 9/8 RT¹
• (B) 3/2 RT¹
• (C) 15/8 RT¹
• (D) 9/2 RT¹

Solution

27 >>Consider an electric field E= E_o xˆ, where E_o is a constant. The flux through the shaded area (as shown in the figure) due to this field ?

• (A) 2E_o a²
• (B) (2)^1/2E_o a²
• (C) E_o a²
• (D) E_o a²/((2)^1/2)

Solution

28 >>A metal rod of length’L’ and mass’m’ is pivoted at one end. A thin disk of mass ’M’ and radius’R’(

• (A) Restoring torque in case A = Restoring torque in case B
• (B) Restoring torque in case A < Restoring torque in case B
• (C) Angular frequency for case A > Angular frequency for case B
• (D) Angular frequency for case A = Angular frequency for case B

Solution Torque about point of suspenstion is same in both case case A : τ = ((MR2/2) + ( ML2) + (ml2/3)) α = k θ case B ; In case B ; Disc is not going to get any torque about its centre. all of its point have acceleration that is equal to acceleration of end point of rod. τ = ((ML2) + (ml2/3)) α = k θ =>W2 = k/((ML2) + (ml2/3)) =>W1 = k/((MR2/2) + ( ML2) + (ml2/3)) =>W2 > W1

29 >>A composite block is made of slabs A, B, C, D and E of different thermal conductivities (given in terms of a constant K) and sizes (given in terms of length, L) as shown in the figure. All slabs are of same width. Heat ’Q’ flows only from left to right through the blocks. Then in steady state ?

• (A) heat flow through A and E slabs are same
• (B) heat flow through slab E is minimum
• (C) temperature difference across slab E is largest
• (D) heat flow through C > (heat flow through B + heat flow through D)

Solution i1 = T/2 = 0.5 T => i2 = 1.2 T =>i3 = 0.7 T => i2 = i1 + i3

30 >>An electron and a proton are moving on straight parallel paths with same velocity. They enter a semi-infinite region of uniform magnetic field perpendicular to the velocity. Which of the following statement(s) is/are true ? ?

• (A) They will never come out of the magnetic field region
• (B) They will come out travelling along parallel paths
• (C) They will come out at the same time
• (D) None of these

Solution r = mv/qB They go in different direction but come out along parallel paths. T = 2(π) m/qB as m is different, so T is also different

31 >>A spherical metal shell A of radius R_A and a solid metal sphere B of radius R_B(< R_A) are kept far apart and each is given charge ’+Q’. Now they are connected by a thin metal wire.Then ?

• (A) E_A^inside > 0
• (B) Q _A < Q _B
• (C) ((σ_A)/(σ_B)) = ((R_A)/(R_B))
• (D) E_A^{on surface} > E_B^{on surface}

Solution 1) EA = 0 2)(QA/RA) = (QB/RQB) =>RA > RB =>QA > QB 3)σ R = V 4) E = σ/(2 Eo

32 >>A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let ’˜N’ be the number density of free electrons, each of mass ’˜m’. When the electrons are subjected to an to electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begin to oscillate about the positive ions with a natural angular frequency ' /omega_p' which is called the palsma frequency. To sustain the oscillations, a time varying electric field needs to be applied that has an angular frequency /omega , where a part of the energy is absorbed and a part of it is reflected. As /omega approaches /omega_p , all the free electrons are set to resonance together and all the energy is reflected. This is the explanation of high reflectivity metals. Taking the electric charge as 'e' and the permittivity as /omega _o' , use dimesional analysis to determine the correct expression for /omega_p . ?

• (A) ((Ne)/(mE_o))^1/2

(B) ((mE_o)/(Ne))^1/2

(C) ((Ne²)/(mE_o))^1/2

(D) ((mE_o)/(Ne²))^1/2

Solution ω = θ/T = T-1 =>D.f. of ((Ne2)/(mEo))1/2 = (((1/L³)*(I²T²)*(ML³T^-2))/(M*(I²T²)))
=> D.f = T^-1

33 >>A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let &#8217N’ be the number density of free electrons, each of mass ’˜m’. When the electrons are subjected to an to electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begin to oscillate about the positive ions with a natural angular frequency ' /omega_p' which is called the palsma frequency. To sustain the oscillations, a time varying electric field needs to be applied that has an angular frequency /omega , where a part of the energy is absorbed and a part of it is reflected. As /omega approaches /omega_p , all the free electrons are set to resonance together and all the energy is reflected. This is the explanation of high reflectivity metals. Estimate the wavelength at which plasma reflection will occur for a metal having the density of electrons N = 4*10²⁷ m^-3 . Take E_o = 10^-11and m =10^-30 , where these quantities are in proper SI units. ?

• (A) 800nm
• (B) 600nm
• (C) 300nm
• (D) 200nm

Solution ω = 2π n => n= (ω)/(2π) =>c=nλ =>λ = c/n = (c2π)/(ω) = 66nm

34 >>Newton's 1st Law is the law of ?

• (A) Inertia
• (B) Force
• (C) Momentum
• (D) Acceleration

Solution Newton's first law of motion - sometimes referred to as the law of inertia. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

35 >>For additional info, click on the i button above. The phase space diagram for simple harmonic motion is a circle centered at the origin. In the figure, the two circles represent the same oscillator but for different initial conditions, and E1 and E2 are the total mechanical energies respectively. Then, ?

• (A) E₁ = 2^1/2E₂
• (B) E₁ = E₂
• (C) E₁ = 4E₂
• (D) E₁ = 16E₂

Solution E = ka2/2 =>E is proportional to a2 =>E1/E2 = 4

36 >>The conduction current in a chemical cell is ?

• (A) By Positive and negative ions
• (B) By Positive ions
• (C) By Negative ions
• (D) By Positive Holes

Solution In the process of the reaction, electrons can be transferred from the zinc to the copper through an electrically conducting path as a useful electric current. An electrochemical cell can be created by placing metallic electrodes into an electrolyte where a chemical reaction either uses or generates an electric current

37 >>Steel wire of length ’L’ at 40°C is suspended from the ceilling and then a mass ’m’ is hung from its free end. The wire is cooled down from 40°C to 30°C to regain its original length ’˜L’. The coefficient of liner thermal expansion of the steel is 10’“5/°C, Young’s modulus of steel is 1011 N/m² and radius of the wire is 1mm. Assume that L>> diameter of the wire. Then the value of ’˜m’ in kg is nearly ?

• (A) 3
• (B) 4
• (C) 5
• (D) 6

Solution Y = mgL/Ae , e=α L δ t =>m=3.14

38 >>The activity of a freshly prepared radioactive sample is 10¹⁰ disintegrations per second, whose mean life is 10⁹s. The mass of an atom of this radioisotope is 10^-23 kg. The mass (in mg) of the radioactive sample is ?

• (A) 1
• (B) 2
• (C) 3
• (D) 4

Solution 1010 = N*1/109 =>N = 1019 =>total mass = 10-25*1019 = 1mg

39 >>A block moving on an inclined plane making an angle 45° with the horizontal and the coefficient of friction is u . The force required to just push it up the inclined plane is 3 times the force required to just prevent from sliging down. If we define N = 10u then N is ?

• (A) 5
• (B) 6
• (C) 7
• (D) 9

Solution

40 >>A boy is pushing a ring of mass 2 kg and radius 0.5 m with a stick a shown in the figure. Then stick applies a force of 2 N on the ring and rolls it without slipping with an acceleration of 0.3m/s2. The coefficient of friction between the ground and the ring is large enough that rolling always occurs and the coefficient of friction between the stick and the ring is (P/10). The value of P is ?

• (A) 4
• (B) 5
• (C) 6
• (D) 7

Solution

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