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One Kg of copper is drawn into a wire of 1mm diameter and a wire of 2 mm diameter. The resistance of the two wires will be in the ratio
An electrical cable having a resistance of 0.2 : delivers 10kw at 200V D.C. to a factory. What is the efficiency of transmission?
A wire of resistance 5Ω is drawn out so that its new length is 3 times its original length.What is the reistance of the new wire?
Two identical cells each of emf E and internal resistance r are connected in parallel with an external resistance R. To get maximum power developed across R, the value of R is
For max. power consumption. I should be max. So denominator should be min. for that
To write the decimal number 37 in binary, how many binary digits are required?
(100101) ⇒ 6 digits
A junction diode has a resistance of 25Ω when forward biased and 2500Ω when reverse biased. The current in the diode, for the arrangement shown will be
R_{eq} = 25 + 10 = 35Ω
Because diode is forward biased. So
If the electron in a hydrogen atom jumps from an orbit with level n_{1 }= 2 to an orbit with level n_{2} = 1 the emitted radiation has a wavelength given by
What is the particle x in the following nuclear reaction:
Hence X represents neutron
An alternating current of rms value 10 A is passed through a 12Ω resistor. The maximum potential difference across the resistor is
I_{rms} = 10A
Which of the following relation represent BiotSavart’s law?
are two vectors given by The magnitude of the component of is
Magnitude of components of
are antiparellel since
The acceleration ‘a’ (in ms^{–2}) of a body, starting from rest varies with time t (in s) following the equation a = 3t + 4 The velocity of the body at time t = 2s will be
a = 3t + 4
Figure below shows the distancetime graph of the motion of a car. If follows from the graph that the car is
Slope is increasing with constant rate. i.e motion is uniformaly accelerated
Two particles have masses m & 4m and their kinetic energies are in the ratio 2: 1. What is the ratio of their linear momenta ?
The force F acting on a particle moving in a straight line is shown below. What is the work done by the force on the particle in the 1st meter of the trajectory ?
Work done in 1 meter = area of shaded curve = 1/2 × 1×5 =2.5 J
If the kinetic energy of a body changes by 20% then its momentum would change by –
Therefore % increase = 9.5%
A bullet is fired with a velocity u making an angle of 60° with the horizontal plane. The horizontal component o the velocity of the bullet when it reaches the maximum height is
Horizontal velocity would be constant so the value of velocity at the highest point will be u/2
A particle is projected at 60° to the horizontal with a kinetic energy K. The kinetic energy at the highest point is
At highest point kinetic energy = 1/2m (v cos 60°)^{2} = 1/4 × 1/2m v^{2} = K/4
The poisson’s ratio of a material is 0.5. If a force is applied to a wire of this material, there is a decrease in the crosssectional area by 4%. The percentage increase in the length is :
Poisson ratio = 0.5
Therefore density is constant hence change in volume is zero we have
That is 4%
Two spheres of equal masses but radii r_{1} and r_{2 }are allowed to fall in a liquid of infinite column. The ratio of their terminal velocities is
We have
Two massless springs of force constants K_{1} and K_{2} are joined end to end. The resultant force constant K of the system is
A spring of force constant k is cut into two equal halves. The force constant of each half is
As
K' = 2K
Two rods of equal length and diameter have thermal conductivities 3 and 4 units respectively. If they are joined in series, the thermal conductivity of the combination would be
In series R = R_{1} + R_{2}
19 g of water at 30° C and 5 g of ice at – 20° C are mixed together in a calorimeter. What is the final temperature of the mixture? Given specific heat of ice = 0.5 cal g^{–1}(°C)^{–1} and latent heat of fusion of ice = 80 cal g^{–1}
5 × .5 × 20 + 5 × 80 + 5t = 19 × 1 × (30 – t)
t = 5°C
. It is difficult to cook rice in an open vessel by boiling it at high altitudes because of
At high altitude pressure is low and boiling point also low
The height of a waterfall is 50 m. If g = 9.8 ms^{–2} the difference between the temperature at the top and the bottom of the waterfall is:
The distance between an object and a divergent lens is m times the focal length of the lens. The linear magnification produced by the lens is
u = – mf
A 2.0 cm object is placed 15 cm in front of a concave mirror of focal length 10 cm. What is the size and nature of the image?
A beam of monochromatic blue light of wavelength 4200 Å in air travels in water of refractive index 4/3. Its wavelength in water will be:
Two identical light waves, propagating in the same direction, have a phase difference G. After they superpose the intensity of the resulting wave will be proportional to
The equation of state for n moles of an ideal gas is PV = nRT, where R is a constant. The SI unit for R is
JK^{–1} mol^{–1}
At a certain place, the horizontal component of earth’s magnetic field is √3 times the vertical component. The angle of dip at that place is
The current flowing through a wire depends on time as I = 3t^{2} +2t + 5. The charge flowing through the cross section of the wire in time from t = 0 to t = 2 sec. is
If the charge on a capacitor is increased by 2 coulomb, the energy stored in it increases by 21%. The original charge on the capacitor is
solving we get q_{i} = 20 coulomb
The work done in carrying a charge Q once around a circle of radius r about a charge q at the centre is
Work done by conservative force in a round trip is zero
Four capacitors of equal capacitance have an equivalent capacitance C_{1} when connected in series and an equivalent capacitance C_{2} when connected in parallel. The ratio is:
Magnetic field intensity H at the centre of a circular loop of radius r carrying current I e.m.u is
In e.m.u system
Which of the following materials is the best conductor of electricity?
Phenol does not liberate CO_{2} from Na_{2 }CO_{3} solution
Note : Strong acid is not formed by weak acid
In which of the following reactions new carboncarbon bond is not formed :
In cannizaro’s reaction no new C–C bond is formed
A compound is formed by substitution of two chlorine for two hydrogens in propane. The number of possible isomeric compounds is
following isomers of C_{3}H_{6 }Cl_{2} is possible
Due to presence of chiral carbon compound (IV) is optically active and forms an enantiomer. So total no of isomers =5
Which one of the following is called a carbylamine?
For making distinction between 2pentanone and 3pentanone the reagent to be employed is
In 2pentanone ie., group is present due to which it can show iodoform test. i.e.,
Which one of the following formulae does not represent an organic compound?
Unsaturation factor = 0, 1, 1, 0.5 Hence (D)
TiCl_{3} + (C_{2}H_{5} )_{3} Al
Which of the following contributes to the double helical structure of DNA
Orlon or PAN
Monomer ⇒ CH_{2} =CH–CN
1 mole of photon, each of frequency 2500 S^{1}, would have approximately a total energy of :
Total Energy = Nhv = 6.022 × 10^{23} × 6.626 × 10^{–34} J.S. × 2500 s^{–1} = 9.9 erg ≈ 10 erg
In (A) option, it should be 10 erg instead of 1 erg.
If nt number of radioatoms are present at time t, the following expression will be a constant :
Hence (C)
The following graph shows how T_{1/2} (halflife) of a reactant R changes with the initial reactant concentration a_{0} .
The order of the reaction will be:
Hence (C)
The second law of thermodynamics says that in a cyclic process :
Because 0 K temperature is unattainable
The equilibrium constant (K) of a reaction may be written as :
ΔGº = –RT lnK
K_{P} = K_{C}(RT)x
If it is assumed that decays only by emitting α and β particles, the possible product of the decay is :
New mass no. = 235 – 2 × 4 = 227
New at. no. = 92 – 2 × 2 + 1 = 92 – 4 + 1 = 89
The time taken for 10% completion of a first order reactin is 20 mins. Then, for 19% completion, the reaction will take
equation (i) / (ii)
∴ t = 40 min.
Which of the following will decrease the pH of a 50 ml solution of 0.01 M HCl?
50 ml 0.01 M ≡ 50 × 0.01 = 0.5
millimole 5 ml 1 (M) ≡ 5 × 1 = 5 millimole
Total millimoles = 5.5 millimole
Total volume = 55 ml.
pH = 1
Equal volumes of molar hydrochloric acid and sulphuric acid are neutralised by dilute NaOH solution and x kcal and y kcal of heat are liberated respectively. Which of the following is true?
Enthalpy of 1 g equivalent of strong acid and 1 g equivalent strong base = 13.7 kcal
Equal volume contains double eq. of H_{2}SO_{4} than HCl
In a group as we go downwards, the oxide basic character increases hence maximum acidic oxide is P_{2}O_{5}
The halflife of a radioactive element is 10 hours. How much will be left after 4 hours in 1 g atom sample?
N = 7.575 × 10^{–1} g atoms
∴ No. of atoms = 7.575 × 10^{–1 }× 6.023 × 10^{23 }atoms = 4.56 × 10^{23 }atoms
For the Paschen series the values of n_{1} and n_{2} in the expression
In Paschen series electron shifting to third shell i.e., n_{1} = 3 to n_{2} = 4, 5, 6,
Under which of the following condition is the relation ΔH = ΔE + PΔV valid for a closed system?
This is applicable when pressure remains constant
An organic compound made of C, H and N contains 20% nitrogen. Its molecular weight is :
Nitrogen at. wt. = 14 in a molecule minimum one atom of N is present
i.e., 20% ≡ 14 Molecular weight = 70
100% ≡ 14 × 5 = 70
In Cuammonia complex, the state of hybridization of Cu^{+2} is
In [Cu(NH_{3})_{4}]^{+}
Cu^{+2} is in a state of dsp^{2} hybridization and shape of the complex is square planar. (One e^{– }is excited from 3d to 4p during complex formation)
The reaction that takes place when Cl_{2} gas is passed through conc. NaOH solution is :
Hence the reaction is disproportionation
Electron is an alloy of Mg(95%) + Zn(4.5%) and Cu(0.5%)
Blackened oil painting can be restored into original form by the action of :
Blackening of oil painting is due to PbS which is oxidised by H_{2}O_{2} to form white PbSO_{4}
PbS + H_{2}O_{2} → PbSO_{4} + H_{2}O
(Black) (white)
Of the following acids the one which has the capability to form complex compound and also possesses oxidizing and reducing properties is :
Here oxidation state of N lies between –3 to +5
Atoms in a P4 molecule of white phosphorus are arranged regularly in the following way :
Silicon exist in nature in combined state as SiO_{2}
4. In aluminium extraction by the Bayer process, alumina is extracted from bauxite by sodium hydroxide at high temperature and pressures :
Solid impurities such as Fe_{2}O_{3} and SiO_{2} are removed and then is reprecipitated :
In the industrial world :
Ethelene can be separated from acetylene by passing the mixture through :
In the compound HC ≡ C  CH = CH_{2} the hybridization of C–2 and C–3 carbons are respectively :
(Double bond is preferred)
I & II are same Fischer projection because 180º rotation doesn't change configuration
Which of the following carbocations will be most stable ?
(Highly resonance stabilized)
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