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The ratio of no. of turns of primary coil to secondary coil in a transformer is 1:2. If a cell of 1.5 V is connected across the primary coil, then e.m.f. across the secondary coil is
The work function of Potassium is 2.0 eV. When it is illuminated by light of wavelength 3300 A0 photoelectrons are emitted. The stopping potential of photoelectrons is
λ = 3300 A0 = 330 nm
hu = 1240/330 = 3.757
eV0 = hu - W = 3.757 - 2 = 1.757eV
⇒ V0 = 1.757 V
Light of wave length λ and photon energy 2eV falling on a metal surface produces photoelectrons of maximum velocity V. If the λ is decreased by 25% and the maximum velocity of electron is doubled, the work function of the metal is (in eV)
A parallel plate capacitor is charged. If the plates are pulled apart
The quantity of electricity needed to liberate one gram equivalent of an element is
Three unequal resistors in parallel are equivalent to resistance 1 Ω . If two of them are in the ratio 1 : 2 and if no resistance value is fractional, the largest of the three resistances in ohms is
The electrical resistance of a mercury column in a cylindrical container is R. When the same mercury is poured into another cylindrical container twice the radius of the first, then resistance of mercury column is
Near a circular loop of conducting wire as shown in the figure an electron moves along a straight line. The direction of the induced current if any in the loop is
A cylinder of radius R and length L is placed in a uniform electric field E parallel to the cylinder axis, the total electric flux for the surface of the cylinder is
Total charge enclosed is zero
When the no. of turns in a coil is triplled, without any change in the length of coil, its self-inductance becomes
An electromagnetic wave passing through vacuum is described by the equations: E = E₀ sin (kx-ωt) and B = B₀ sin (Kx-ωt). Then
Equal charges are given to two spheres of different radii. The potential will be
On moving a charge of 20 C by 2 cm, 2 joule of work is done, then the potential difference between the points is
W = QV
∴ V = W/Q = 2/20 = 0.1 volt
If n capacitors each of capacitance C are connected in series with a battery of V volt, then electrostatic energy stored in all the capacitors will be
The equivalent capacitance Cs of these series-connected capacitors is
1/Cs = 1/C + 1/C + 1/C ..... n times = n/C
∴ Cs = C/n
Energy stored in all capacitors = 1/2 CsV2 = 1/2 C/n V2 = 1/2n CV2
There is 10 units of charge at the centre of a circle of radius 10m. The work done in moving 1 unit of charge around the circle once is
Two point charges each equal to 2μC are 0.5 m apart. If both of them exist inside vaccum, then electrostatic force between them is
By using F = 9 x 109 . Q2/r2
Two long parallel wires carry equal current in opposite directions. They will
A radio active sample has a half life of 5 days. To decay from 8 micro curies to 1 micro-curie, the number of days taken will be
In a nuclear reactor, material used for control rods is
A radioactive element has a half life of 15 years. The fraction that will decay in 30 years is
If the intensity of light falling on a metal is decreased then
By increasing the intensity of incident light on the surface of a metal
A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be
m = -3, m = - v u
-3 = - v/ -20
⇒ v = - 60 cm
Now, u = - 20, v = - 60, f = ?
1/f = 1/v + / u
= - 1/60 - 1/20 = - 1 - 3/60 = - 4/ 60
∴ f = - 60/4 = - 15 cm
The p-n junction diode works as insulator, if connected
the amplifiers do not work to their proper form when used in a circuit if
When the forward bias voltage increases what happens to the potential barrier.
To obtain a p-type germanium semiconductor, it must be doped with
The most commonly used material for making transistor is
The depletion layer in the P-N junction region is caused by
In a Young's experiment, two coherent sources are placed 0.90 mm apart and the fringes are observed one metre away. If it produces the second dark fringe at a distance of 1 mm from the central fringe, the wavelength of monochromatic light used would be
In Huygen's wave theory, the locus of all points oscillating in the same phase is called a
Which of the following phenomena establish the wave nature of light?
Laser light is considered to be coherent as it consists of
Formaldehyde reacts with NaOH(50%). Which one pair of products will be obtained?
Which of the following does not give red ppt. with Fehling solution?
From which of the following tertiary butyl alcohol is obtained by the action of methyl megnesium iodide?
How many monochlorobutanes will be obtained on chlorination of n-butane?
The ratio of the molar amounts of H₂S needed to precipitate the metal ions from 20 mL each of 1M Cd(NO₃)₂ and 0.5 M CuSO₄ is
As Cd2+ and Cu2+, both are dipositive ions but Cu2+ has one half of the concentration compared to that of the Cd2+. Thus, the molar amount of the H2S used to precipitate the metals ions Cd2+ and Cu2+ is 2 : 1.
A sequence of how many nucleotides in m-RNA makes a codon for an amino acid?
In a chemical equilibrium Kc = Kp when :
Kp = Kc when Δn = 0
Which one of the following informations can be obtained on the basis of Le Chatelier principle ?
Which of the following gas molecule has the maximum specific heat at constant pressure?
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)
A complex compound of Co3+ with molecular formula CoClxyNH₃ gives a total of three ions per molecule when dissolved in water. How many Cl⁻ ions satisfy primary as well secondary valencies in this complex?
A smuggler could not carry gold by chemically depositing iron on the gold surface since
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
If half cell reaction A + e- → A- has a large negative reduction potential, it follows that
Which one of the following indicates the value of the gas constant R ?
White P when boiled with strong solution of caustic soda produces
AB is an ionic solid. If the ratio of ionic radii of A+ and B − is 0.52. What is the coordination number of B −
Ratio r+/r - = 0.414 - 0.732
Coordination no. is 6.
Which of the following is an example of homogeneous catalysis?
Which forms meso form on reaction with alkaline KMnO4?
Fill in the blank with appropriate word.
If a speech is full of pompous words, it is.........
Choose the alternative which best expresses the meaning of the idiom/phrase.
To be under a cloud
Improve the sentence by choosing best alternative for capitalised part of the sentence.
No sooner did HIS FEET TOUCHED the ground than the intensity of the disaster dawend upon him.