The efficiency of transformer is very high because
An electron and a proton have the same wave length. Which one of the following statements is correct about them?
The work function of metals A and B are in the ratio 1 : 2. If light of frequencies f and 2f are incident on metal surfaces of A and B respectively, the ratio of the maximum kinetic energies of photo electrons emitted is (f is greater than threshold frequency of A, 2f is greater than thershold frequency of B)
A sheet of aluminium is inserted in the air gap between the parallel plate capacitor, without touching any the two plates of the capacitor. The capacitance the capacitor is:
If sky wave with a frequency of 50 MHz is incident on D-region at an angle of 30o, then angle of refraction is
The resistance of a cell does not depend upon
Two resistance wires on joining in parallel the resultant resistance is 6/5 ohms. One of the wire breaks, the effective resistance is 2 ohms. The resistance of the broken wire is
When a wire of resistance R is stretched and its radius becomes r/2, then the new resistance will be
Two resistances 4 Ω and 6 Ω are in series and another 10Ω resistance is in parallel to the series combination. The resultant resistance is
Which of the following materials is the best conductor of electricity?
Particle nature is shown by
A transformer is used to light a 100W and 110V lamp from a 220V mains. If the main current is 0.5A, the efficiency of the transformer is approximately
A coil carrying electric current is placed in uniform magnetic field, then
The coil carrying current held in a magnetic field experiences a torque.
When the no. of turns in a coil is triplled, without any change in the length of coil, its self-inductance becomes
Which rays are not the portion of electro magnetic spectrum?
If the electric flux entering and leaving an enclosed surface respectively is φ₁ and φ₂, the electric charge inside the surface will be
n small drops of same size are charged to V volt each. They coalesce to form a bigger drop. The potential of the bigger drop is
A spherical shell of radius a with charge Q is expanded to radius b. The work done by the electric force in the process is
A charge q is located at the centre of a cube. The electric flux through any face is
A body of mass 1g and carrying a charge 10-8, C passes from two points P and Q. P and Q are at electric potentials 600V and 0V respectively. The velocity of the body at Q is 20 c m s-1 . Its velocity in m s-1 at P is
The electrical conductivity of the earth's atmosphere increases with altitude due to
A current carrying coil when freely suspended will allign itself
The first atomic reactor was constructed by
In two isotopes of an element the number of protons in their nuclei will be --- and number of neutrons in their nuclei will be
Which one of the following is a possible nuclear reaction?
When the photons of energy hv fall on a photo-sensitive surface (work function hv₀) electrons are emitted from the metallic surface. This is known as photoelectric effect. The electron coming out of the surface have a kinetic energy. Then it is possible to state that
The threshold wavelength is 2000 Å. The work function is
A symmetric double convex lens is cut in two equal parts by a plane perpendicular to the principal axis. It the power of the original lens is 4D, the power of a cut lens will be
The difference in the number of wavelengths, when yellow light propagates through air and vacuum columns of the same thickness, is one. The thickness of the air column is
(Refractive index of air μa = 1.0003 ; Wavelength of yellow light in vacuum 6000 Å )
Let λa and λ be the wavelengths of yellow light in air and vacuum respectively and va and c be their respective speeds in air and vacuum.
Since the frequency of light is the same in both media, we have
Now, if t is the thickness of each columm, then the number of wavelengths in the two media are
Given μ a = 1.0003 and λ = 6000 Å = 6000 x 10 − 8 cm. Using these values in (3), we have
When Boron is added as impurity to silicon, the resulting material is -------- semiconductor.
In the middle of the depletion layer of a reverse-biased p-n junction, the
In a p - type semiconductor, the electrical conduction is due to
At OK temperature, a p-type semiconductor
The band gap in germanium and silicon in eV respectively is
When the electrical conductivity of a semiconductor is due to the breaking of its covalent bonds, then the semiconductor is said to be
A example of a semiconductor is
A train is approaching a platform with a velocity ν. The frequency heard by an observer standing at the station is
A wave front is the locus of all the particles of a medium, which are vibrating in the
If the two slits in Young's experiment have width ratio 1:4, the ratio of intensity at maxima and minima in the interference pattern in
Two slits, 4 mm apart, are illuminated by light of wavelength 6000 Å. What will be the fringe width on a screen placed 2 m from the slits?
Which of the following processes is employed to convert alkyl halide into alcohol?
In which reaction aromatic aldehyde is treated with acid anhydride in presence of corresponding salt of the acid to give unsaturated aromatic acid?
Which of the following will give Cannizzaro reaction?
The functional group present in 3-methyl butanal is
Methane is formed when
Assume that the nucleus of the fluorine atom is a sphere of radius 5 x 10-13 cm. What is the density of matter in the nucleus?
The radius of a fluorine nucleus is x 10-13 cm
The mass of a F nucleus = 19/6 x 1023 g = 3.2 x 10-26 kg
The volume of a F nucleus = 4 3 πr3
= 4/3 x π x (5 x 10-13)3 cm3
= 5.2 x 10-37 cm3
Density = mass/volume
= 3.2 x 10 -26 k g /5.2 x 10-37 c m3
= 6.1 x 1010 kg cm-3 = 6.1 x 1013 g cm-3
Acid catalysed hydration of alkenes except ethene leads to the formation of
The three fundamental quantities are
An antibody is a/an
Which of the following is not a function of proteins?
The metal present in vitamin B₁₂ is
Amides may be converted into amines by a reaction named after
From the following values of dissociation constants of four acids which value represents the strongest acid ?
Which of the following gives blood red colour with KCNS ?
Which of the following compounds on boiling with KMnO₄ and the subsequent acidification will not give benzoic acid ?
A vessel at equilibrium, contains SO₃, SO₂ and O₂. Now some helium gas is added, so that total pressure increases while temperature and volume remain constant. According to Le-Chatelier's principle, the dissociation of SO₃
If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then
Which of the following is not chiral ?
The heats of dissociation (k.cals/mole) of methane and ethane are 360 and 620 respectively. From these, C - C bond energy (k.cals/mole) in ethane can be evaluated as
Which one of the following will not show geometrical isomerism?
Work done during the compression of a gas from a volume of 6dm3 to 4 dm3 against a constant external pressure of 3 atm is (1atm-litre=101.32J)
Which of the following could act as a propellant for rockets?
The cell potential of the following cell at 25 oC (in volts) is
Which of the following metal does not form polynuclear carbonyl?
Compound A has a molecular formula C₇H₇NO on treatment with Br₂/KOH, A gives an amine B which respond to carbylamine test. B on diazotisation and coupling with phenol give an azo dye. A can be
Ethyl isocyanide on acidic hydrolysis generates
A smuggler could not carry gold by chemically depositing iron on the gold surface since
Calculate the amount of change flowing in 2 minute in a wire of resistance 10 Ω when a potential difference of 20 V is applied
Which is most explosive?
In the preparation of sodium carbonate (Na₂CO₃), which of the following is used as raw material?
Which one of the following indicates the value of the gas constant R ?
Glass is a
The three important oxidation states of phosphorus are
When ether is exposed in air for sometime, an explosive substance produced is
xMnO₄- + yH₂SO₄ → 2Mn2+ + 5H₂O +9O₂ + ze- In this reaction values of x, y and z are
Which of the following has maximum Frenkel defect?
In the extraction of iron, slag is produced which is
(2R, 3R)- 2, 3-butanediol is:
A transition metal x has configuration [Ar]3d4 in its +3 oxidation state. Its atomic number is
Cod Liver oil is
Find the synonym of SUSTAIN
Fill in the blank with appropriate word.
Our flight was.........from Jaipur to Agra airport.
Find the antonym of COVERT
Choose the alternative which best expresses the meaning of the idiom/phrase.
To follow the primrose path
Improve the sentence by choosing best alternative for capitalised part of the sentence.
My mother asked me when WOULD I have a glass of milk.