NEET UG
- In an experiment, the percentage of error occurred in the measurement of physical quantities A, B, C and D are 1%, 2%, 3% and 4% respectively. Then the maximum percentage of error in the measurement X, where X = A^2 B^1/2C^1/3 D^3, will be : Answer: 2. 16% For a product or quotient, the maximum fractional error is the sum of each power times its fractional error. Δ X/X×100=2(1)+1... 1
- In which of the following processes, heat is neither absorbed nor released by a system ? Answer: 2. adiabatic In an adiabatic process Δ Q=0 by definition: no heat enters or leaves the system. In isothermal, isobaric and isochoric... 1
- The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively : Answer: 3. 3.4 eV, -6.8 eV For an electron in a bound orbit, KE=-E and PE=2E . With E=-3.4 eV: KE=+3.4 eV and PE=-6.8 eV. Check: 3.4-6.8=-3.... 1
- α-particle consists of : Answer: 1. 2 protons and 2 neutrons only An α -particle is the nucleus of a helium atom, ⁴₂He : 2 protons and 2 neutrons, with no electrons. 1
- Which of the following acts as a circuit protection device ? Answer: 4. fuse A fuse contains a thin wire that melts when the current exceeds a safe limit, breaking the circuit and protecting the applia... 1
- Six similar bulbs are connected as shown in the figure with a DC source of emf E, and zero internal resistance.The ratio of power consumption by the bulbs when (i) all are glowing and (ii) in the situation when two from section A and one from section… Answer: 2. 9 : 4 From the figure, the three bulbs of section A are in parallel with each other, as are the three bulbs of section B. The two... 1
- In the circuits shown below, the readings of the voltmeters and the ammeters will be : Answer: 3. V₁ = V₂ and i₁ = i₂ Treat the voltmeters as ideal (infinite resistance), so they draw no current. Circuit 1: the 10 Ω resistor is... 1
- An electron is accelerated through a potential difference of 10,000 V. Its de Broglie wavelength is, (nearly) : (m_e = 9×10^-31 kg) Answer: 2. 12.2×10⁻¹² m de Broglie wavelength of an electron accelerated through V : λ=h/√(2meV) . Substituting h=6.63×10⁻³⁴ , m=9×10⁻³¹ , e... 1
- For a p-type semiconductor, which of the following statements is true ? Answer: 2. Holes are the majority carriers and trivalent atoms are the dopants. A p-type semiconductor is made by doping silicon or germaniu... 1
- Two point charges A and B, having charges +Q and -Q respectively, are placed at certain distance apart and force acting between them is F. If 25% charge of A is transferred to B, then force between the charges becomes : Answer: 2. 9F/16 25% of A's charge is 0.25Q . After transfer: q_A=0.75Q and q_B=-Q+0.25Q=-0.75Q . Coulomb force F∝ q_Aq_B at the same distan... 1
- Two parallel infinite line charges with linear charge densities +λ C/m and -λ C/m are placed at a distance of 2R in free space. What is the electric field mid-way between the two line charges ? Answer: 3. λ/πε₀ R N/C The field of an infinite line charge at distance r is E=λ/2πε₀r . Midway, r=R for each line. The + λ line pushes away... 1
- A hollow metal sphere of radius R is uniformly charged. The electric field due to the sphere at a distance r from the centre : Answer: 2. zero as r increases for r < R, decreases as r increases for r > R For a uniformly charged hollow sphere, by Gauss's law: Inside (... 1
- A body weighs 200 N on the surface of the earth. How much will it weigh half way down to the centre of the earth ? Answer: 4. 100 N Inside the earth at depth d , g'=g(1-d/R) . Halfway to the centre means d=R/2 , so g'=g/2 . Weight =200/2=100 N. 1
- The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth, is : Answer: 3. 1/2mgR Work done = change in gravitational potential energy. W=-GMm/R+h+GMm/R . With h=R : W=GMm(1/R-dfrac12R)=GMm/2R . Using GM=... 1
- The speed of a swimmer in still water is 20 m/s. The speed of river water is 10 m/s and is flowing due east. If he is standing on the south bank and wishes to cross the river along the shortest path, the angle at which he should make his strokes w.r.… Answer: 1. 30^° west To cross along the shortest path (straight north), the swimmer's velocity component along the river flow must cancel th... 1
- Two particles A and B are moving in uniform circular motion in concentric circles of radii r_A and r_B with speed v_A and v_B respectively. Their time period of rotation is the same. The ratio of angular speed of A to that of B will be : Answer: 4. 1 : 1 Angular speed ω=2π/T . Both particles have the same period T , so they have the same angular speed. ω_A:ω_B=1:1 . (Their li... 1
- When an object is shot from the bottom of a long smooth inclined plane kept at an angle 60^° with horizontal, it can travel a distance x_1 along the plane. But when the inclination is decreased to 30^° and the same object is shot with the same veloci… Answer: 3. 1:√(3) On a smooth incline the retardation is gsinθ . For the same launch speed v , the distance up the plane is x=v²/2gsinθ , so... 1
- Increase in temperature of a gas filled in a container would lead to : Answer: 2. increase in its kinetic energy The temperature of a gas measures the average kinetic energy of its molecules. Raising the tempera... 1
- A particle moving with velocity V is acted by three forces shown by the vector triangle PQR. The velocity of the particle will : Answer: 3. remain constant In the figure the three vectors overrightarrowPQ,overrightarrowQR,overrightarrowRP are placed head to tail and fo... 1
- A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to ke… Answer: 3. 10 rad/s The wall's normal force supplies the centripetal force: N=mω²r . Friction balances weight: μ N=mg . μ mω²r=mg⇒ω=√(g/μ r)... 1
- At a point A on the earth's surface the angle of dip, δ = +25^°. At a point B on the earth's surface the angle of dip, δ = -25^°. We can interpret that : Answer: 3. A is located in the northern hemisphere and B is located in the southern hemisphere. The angle of dip is positive (the north pole... 1
- Two similar thin equi-convex lenses, of focal length f each, are kept coaxially in contact with each other such that the focal length of the combination is F_1. When the space between the two lenses is filled with glycerin (which has the same refract… Answer: 2. 1 : 2 Two thin lenses in contact: dfrac1F₁=1/f+1/f , so F₁=f/2 . When the gap is filled with glycerin of the same index as glass,... 1
- Pick the wrong answer in the context with rainbow. Answer: 3. An observer can see a rainbow when his front is towards the sun. We pick the wrong statement. Two internal reflections give the s... 1
- In total internal reflection when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction ? Answer: 4. 90^° At the critical angle C , Snell's law gives μ₁sin C=μ₂sin r with sin C=μ₂/μ₁ . So sin r=1 and r=90^° : the refracted ray gra... 1