#neet
- An ideal gas undergoes four different processes from the same initial state as shown in the figure below. Those processes are adiabatic, isothermal, isobaric and isochoric. The curve which represents the adiabatic process among 1, 2, 3 and 4 is : Answer: 3. 2 On a P-V diagram, all processes start from the same point. Curve 1 is vertical (constant volume, isochoric) and curve 4 is hori... 1
- The ratio of the distances travelled by a freely falling body in the 1^st, 2^nd, 3^rd and 4^th second : Answer: 4. 1 : 3 : 5 : 7 For a body falling from rest, the distance in the n th second is s_n=1/2g(2n-1) . So the distances in 1st, 2nd, 3rd... 1
- Two objects of mass 10 kg and 20 kg respectively are connected to the two ends of a rigid rod of length 10 m with negligible mass. The distance of the center of mass of the system from the 10 kg mass is : Answer: 3. 20/3 m Place the 10 kg mass at the origin and the 20 kg mass at 10 m. x_cm=10(0)+20(10)/10+20=200/30=20/3\ m The centre of mass l... 1
- The energy that will be ideally radiated by a 100 kW transmitter in 1 hour is : Answer: 2. 36 × 10⁷ J Energy radiated equals power times time. E=Pt=100×10³\ W×3600\ s=3.6×10⁸\ J=36×10⁷\ J Option (2) is correct. 1
- An electric lift with a maximum load of 2000 kg (lift + passengers) is moving up with a constant speed of 1.5 ms^-1. The frictional force opposing the motion is 3000 N. The minimum power delivered by the motor to the lift in watts is : (g = 10 ms^-2) Answer: 4. 34500 At constant speed the motor force balances weight plus friction. F=mg+f=2000×10+3000=23000\ N P=Fv=23000×1.5=34500\ W Optio... 1
- A copper wire of length 10 m and radius (10^-2/√(π)) m has electrical resistance of 10 Ω. The current density in the wire for an electric field strength of 10 (V/m) is : Answer: 1. 10⁵ A/m ² Current density is J=σ E=E/ρ , so first find resistivity from R=ρ L/A . A=π r²=π·dfrac10⁻⁴π=10⁻⁴\ m² ρ=RA/L=dfrac10×10⁻... 1
- If a soap bubble expands, the pressure inside the bubble : Answer: 2. decreases Excess pressure inside a soap bubble is Δ P=4S/r , so it is inversely proportional to the radius. When the bubble expan... 1
- Given below are two statements :Statement I : Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element (Idl) of a current carrying conductor only.Statement II : Biot-Savart's law is analogous to Co… Answer: 4. Statement I is correct and Statement II is incorrect Statement I: Biot-Savart law gives the field due to a small current element... 1
- A shell of mass m is at rest initially. It explodes into three fragments having mass in the ratio 2 : 2 : 1. If the fragments having equal mass fly off along mutually perpendicular directions with speed v, the speed of the third (lighter) fragment is… Answer: 4. 2√(2) v The shell is at rest, so total momentum after explosion is zero. Masses are 2m/5,\ 2m/5 and m/5 . The two equal fragments... 1
- A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball (v) as a function of time (t) is : Answer: 3. B A ball dropped in a viscous liquid starts with acceleration g . As speed grows, viscous drag rises, so the acceleration falls t... 1
- The angular speed of a fly wheel moving with uniform angular acceleration changes from 1200 rpm to 3120 rpm in 16 seconds. The angular acceleration in rad/s^2 is : Answer: 3. 4π Convert rpm to rad/s using ω=2π N/60 . Δ N=3120-1200=1920 rpm, so Δω=2π×1920/60=64π\ rad/s . α=Δω/t=64π/16=4π\ rad/s² . Option... 1
- The peak voltage of the ac source is equal to : Answer: 4. √(2) times the rms value of the ac source For a sinusoidal ac, V_rms=V₀/sqrt2 , so the peak value is V₀=sqrt2 V_rms . Option (4)... 1
- The displacement-time graphs of two moving particles make angles of 30° and 45° with the x-axis as shown in the figure. The ratio of their respective velocity is : Answer: 1. 1 : √(3) On a displacement-time graph, velocity equals the slope, v=tanθ . v₁/v₂=tan30^°/tan45^°=1/sqrt3/1=1:sqrt3 . The 30 degre... 1
- In the given circuits (a), (b) and (c), the potential drop across the two p-n junctions are equal in : Answer: 1. Both circuits (a) and (c) Two diodes in series with a battery see the same current, so their voltage drops are equal when both ar... 1
- The angle between the electric lines of force and the equipotential surface is : Answer: 4. 90° Work done in moving a charge along an equipotential surface is zero, so the field has no component along the surface. Hence e... 1
- In a Young's double slit experiment, a student observes 8 fringes in a certain segment of screen when a monochromatic light of 600 nm wavelength is used. If the wavelength of light is changed to 400 nm, then the number of fringes he would observe in… Answer: 1. 12 Fringe width is β=λ D/d . For a fixed region of the screen, the number of fringes is N∝ 1/β∝ 1/λ . N₂=N₁λ₁/λ₂=8×600/400=12 Opt... 1
- A light ray falls on a glass surface of refractive index √(3), at an angle 60°. The angle between the refracted and reflected rays would be : Answer: 4. 90° Use Snell's law: sin60^°=sqrt3sin r⇒sin r=1/2⇒ r=30^° . The reflected ray makes 60^° with the normal, the refracted ray 30^°... 1
- In half wave rectification, if the input frequency is 60 Hz, then the output frequency would be : Answer: 4. 60 Hz A half-wave rectifier conducts only in one half of each ac cycle, so there is one output pulse per input cycle. Output freq... 1
- A body of mass 60 g experiences a gravitational force of 3.0 N, when placed at a particular point. The magnitude of the gravitational field intensity at that point is : Answer: 3. 50 N/kg Gravitational field intensity is force per unit mass: E=F/m . m=60\ g=0.06\ kg⇒ E=3.0/0.06=50\ N/kg . Option (3). Using 6... 1
- A square loop of side 1 m and resistance 1 Ω is placed in a magnetic field of 0.5 T. If the plane of loop is perpendicular to the direction of magnetic field, the magnetic flux through the loop is : Answer: 3. 0.5 weber Flux is φ=BAcosθ . The plane of the loop is perpendicular to the field, so the normal is parallel to B and θ=0 . φ=0.5×... 1
- Let T_1 and T_2 be the energy of an electron in the first and second excited states of hydrogen atom, respectively. According to the Bohr's model of an atom, the ratio T_1 : T_2 is : Answer: 1. 9 : 4 In Bohr's model the energy magnitude is E_n∝ 1/n² . First excited state is n=2 and second excited state is n=3 . T₁/T₂=1/4/... 1
- A long solenoid of radius 1 mm has 100 turns per mm. If 1 A current flows in the solenoid, the magnetic field strength at the centre of the solenoid is : Answer: 3. 12.56 × 10⁻² T Field at the centre of a long solenoid is B=μ₀ nI . n=100 turns/mm =10⁵ turns/m. B=4π×10⁻⁷×10⁵×1=0.1256\ T=12.56×1... 1
- Two pendulums of length 121 cm and 100 cm start vibrating in phase. At some instant, the two are at their mean position in the same phase. The minimum number of vibrations of the shorter pendulum after which the two are again in phase at the mean pos… Answer: 2. 11 Time period T∝sqrt l , so T₁₂₁:T₁₀₀=11:10 . They are next in phase when the shorter pendulum has made one more vibration than... 1
- The Adenosine deaminase deficiency results into : Answer: 1. Dysfunction of Immune system Adenosine deaminase (ADA) deficiency damages lymphocytes and causes severe combined immunodeficiency... 1