NEET UG

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The capacitance of a parallel plate capacitor with air as medium is 6 μF. With the introduction of a dielectric medium, the capacitance becomes 30 μF. The permittivity of the medium is :(ε_0 = 8.85×10^-12 C^2 N^-1 m^-2) Answer: 3. 0.44×10⁻¹⁰ C ² N ⁻¹ m ⁻² Capacitance with a dielectric of relative permittivity K is C=KC₀ . So K=30/6=5 Permittivity of the medi... Capacitors, series and parallel combination, parallel plate capacitor with/without dielectric 1 answer
A short electric dipole has a dipole moment of 16×10^-9 C m. The electric potential due to the dipole at a point at a distance of 0.6 m from the centre of the dipole, situated on a line making an angle of 60^° with the dipole axis is :≤ft(1/4πε_0 = 9… Answer: 2. 200 V Potential of a short dipole: V=1/4πε₀pcosθ/r² . V=frac9×10⁹×16×10⁻⁹×cos60^°(0.6)²=144×0.5/0.36=200\ V Answer: option 2. Electric dipole, field due to dipole, torque in uniform field 1 answer
A ball is thrown vertically downward with a velocity of 20 m/s from the top of a tower. It hits the ground after some time with a velocity of 80 m/s. The height of the tower is : (g = 10 m/s^2) Answer: 4. 300 m Use v²=u²+2gh (downward motion, g positive). h=v²-u²/2g=80²-20²/2×10=6400-400/20=300\ m Answer: option 4. Uniformly accelerated motion relations 1 answer
The average thermal energy for a mono-atomic gas is : (k_B is Boltzmann constant and T, absolute temperature) Answer: 2. 3/2k_BT A monoatomic gas molecule has only 3 translational degrees of freedom. By the equipartition law each gives 1/2k_BT . E=3×... Kinetic interpretation of temperature, RMS speed 1 answer
Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity (g) is : Answer: 3. g/5 Atwood machine: the heavier mass moves down, and both masses share the same acceleration. a=(m₂-m₁)g/m₁+m₂=(6-4)g/6+4=g/5 Ans... Newton's laws, force and inertia, momentum, impulse 1 answer
A long solenoid of 50 cm length having 100 turns carries a current of 2.5 A. The magnetic field at the centre of the solenoid is :(μ_0 = 4π×10^-7 T m A^-1) Answer: 1. 6.28×10⁻⁴ T Field inside a long solenoid: B=μ₀nI , with n turns per metre. n=100/0.5=200\ m⁻¹ B=4π×10⁻⁷×200×2.5=6.28×10⁻⁴\ T Answ... Ampere's law: straight wire and solenoid 1 answer
An iron rod of susceptibility 599 is subjected to a magnetising field of 1200 A m^-1. The permeability of the material of the rod is :(μ_0 = 4π×10^-7 T m A^-1) Answer: 1. 2.4π×10⁻⁴ T m A ⁻¹ Relative permeability μ_r=1+chi=1+599=600 . μ=μ₀μ_r=4π×10⁻⁷×600=2.4π×10⁻⁴\ T m A⁻¹ The magnetising field 1200... Para-, dia- and ferromagnetism, effect of temperature 1 answer
In Young's double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes : Answer: 3. four times Fringe width β=λ D/d . With d→ d/2 and D→2D : β'=λ(2D)/d/2=4β The fringe width becomes four times. Answer: option 3. Interference and Young's double-slit experiment 1 answer
Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is : Answer: 1. 3.66×10⁻⁷ rad Limit of resolution of a telescope: Δθ=1.22λ/D . Δθ=frac1.22×600×10⁻⁹2=3.66×10⁻⁷\ rad Answer: option 1. Microscope and astronomical telescope 1 answer
Dimensions of stress are : Answer: 4. [ML⁻¹T⁻²] Stress =force/area . [stress]=frac[MLT⁻²][L²]=[ML⁻¹T⁻²] This is the same as the dimensions of pressure. Answer: option... Dimensions and dimensional analysis 1 answer
Taking into account of the significant figures, what is the value of 9.99 m - 0.0099 m ? Answer: 2. 9.98 m For subtraction, the result keeps as many decimal places as the number with the fewest decimal places. 9.99 has 2 decimals... Least count, significant figures and errors in measurement 1 answer
The energy required to break one bond in DNA is 10^-20 J. This value in eV is nearly : Answer: 3. 0.06 Convert joules to eV using 1\ eV=1.6×10⁻¹⁹ J. E=frac10⁻²⁰1.6×10⁻¹⁹=0.0625≈0.06\ eV Answer: option 3. Units of measurement, SI units, fundamental and derived units 1 answer
A wire of length L, area of cross section A is hanging from a fixed support. The length of the wire changes to L_1 when mass M is suspended from its free end. The expression for Young's modulus is : Answer: 4. MgL/A(L₁ - L) Young's modulus Y=stress/strain . Stress =Mg/A Strain =L₁-L/L , since the extension is L₁-L and the original length... Elastic behaviour, stress-strain, Hooke's law, Young's, bulk and rigidity moduli 1 answer
The quantities of heat required to raise the temperature of two solid copper spheres of radii r_1 and r_2 (r_1 = 1.5 r_2) through 1 K are in the ratio : Answer: 1. 27/8 Heat needed for a 1 K rise is Q=mcΔ T . Both spheres are copper, so c is the same and Q∝ m∝ r³ . Q₁/Q₂=(r₁/r₂)³=(1.5)³=27/8... Specific heat capacity, calorimetry, change of state, latent heat 1 answer
A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of the water in the capillary is 5 g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is : Answer: 3. 10.0 g Capillary rise: h=2Tcosθ/rρ g , so h∝1/r . Mass of water in the tube m=ρπ r²h∝ r²·1/r=r . Radius doubled gives mass double... Surface energy, surface tension, angle of contact, excess pressure, drops, bubbles, capillary rise 1 answer
The rate constant for a first order reaction is 4.606×10^-3 s^-1. The time required to reduce 2.0 g of the reactant to 0.2 g is : Answer: 3. 500 s For a first-order reaction t=2.303/klog[A]₀/[A] . t=frac2.3034.606×10⁻³log2.0/0.2=frac2.3034.606×10⁻³×1=500\ s Answer: opti... Integrated rate equations and half-life (zero and first order) 1 answer
Match the following :Oxide | Nature(a) CO (i) Basic(b) BaO (ii) Neutral(c) Al_2O_3 (iii) Acidic(d) Cl_2O_7 (iv) AmphotericWhich of the following is correct option ? Answer: 2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii) CO: neutral oxide (a)-(ii). BaO: basic oxide of an s-block metal (b)-(i). Al₂O₃ : amphoter... Valence, oxidation states and chemical reactivity 1 answer
An alkene on ozonolysis gives methanal as one of the product. Its structure is : Answer: 3. Cyclohexyl-CH ₂ -CH=CH ₂ Ozonolysis cleaves C=C and gives a carbonyl on each carbon. Methanal (HCHO) comes only from a terminal =... Alkenes: ozonolysis and polymerization 1 answer
Which of the following alkane cannot be made in good yield by Wurtz reaction ? Answer: 3. n-Heptane The Wurtz reaction ( 2RX+2Na→ R-R ) gives good yield only when both alkyl groups are the same, so one alkyl halide is u... Classification, isomerism, nomenclature, preparation 1 answer
Anisole on cleavage with HI gives : Answer: 1. Phenol (C ₆ H ₅ OH) + CH ₃ I Aryl alkyl ethers are cleaved by HI at the alkyl-oxygen bond. The ether oxygen is protonated, then I... Ethers 1 answer
For which one of the following, Bohr model is not valid ? Answer: 4. Singly ionised neon atom (Ne ^+ ) The Bohr model works only for one-electron (hydrogen-like) systems, where the electron feels ju... Bohr model, energy levels, hydrogen spectrum 1 answer
The energy equivalent of 0.5 g of a substance is : Answer: 2. 4.5×10¹³ J Use Einstein's mass-energy relation E=mc² . E=0.5×10⁻³×(3×10⁸)²=4.5×10¹³\ J Answer: option 2. Remember to convert gram... Mass-energy relation, mass defect, binding energy per nucleon 1 answer
The solids which have the negative temperature coefficient of resistance are : Answer: 4. insulators and semiconductors Metals have a positive temperature coefficient of resistance: resistance rises with temperature as... Resistivity, conductivity and temperature dependence of resistance 1 answer
Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled ? Answer: 4. zero Photoelectric emission needs frequency ν≥ν₀ , whatever the intensity. Initially ν=1.5ν₀ . Halved, it becomes 0.75ν₀<ν₀ , bel... Photoelectric effect, Hertz and Lenard's observations 1 answer

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