The radio activity of an element becomes 1/64th of original value in 60 sec. Then the half life period is
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An unknown resistance K₁ is connected in series with a resistance of 10 Ω. This combination is connected to one gap of a metre bridge, while a resistance K₂ is connected in the other gap. The balance point is at 50 cm. Now when the 10 Ω resistance is removed, the balance point shifts to 40 cm. The value of K₁ is
Consider the two following statements A and B and identify the correct choice given in the answers; (A) In photovoltaic cells the photoelectric current produced is not proportional to the, intensity of incident light. (B) in gas filled photoemissive cells, the velocity of photoelectrons depends on the wavelength of the incident radiation.
Which of the following does not obey the phenomenon of mutual induction?
Compare electrons accelerated through a certain potential difference and protons accelerated through the same p.d. If initial velocities are negligible, then the emergent
If 2.2 kW power is transmitted through a 10 Ω line at 22000 V, the power loss in the form of heat will be
In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor, when the energy is stored equally between the electric and magnetic field is
A parallel plate capacitor is first charged and then a dielectric slab is introduced between the plates. The quantity that remains unchanged is
A uniform wire of 16Ω resistance is made into the form of a square. Two opposite corners of the square are connected by a wire of resistance 16Ω. The effective resistance between the other two opposite corners is
If 4 x 1020 eV of energy is required to move a charge of 0.25 coluomb between two points, the P.D. between them is
The value of g on the earth's surface is 980 cm/sec2. Its value at a height of 64 km from the earth's surface is
A black body, at a temprature of 227°C, radiates heat at a rate of 20 cal m⁻2s⁻1. When its temperature is raised to 727° the heat radiated by it in cal m⁻2s⁻1 will be closest to
Capacitance of a capacitor becomes 7/6 times its original value if a dielectric slab of thickness, t = 2/3 d is introduced in between the plates. 'd' is the separation between the plates. The dielectric constant of the dielectric slab is
At OK which of the following properties of a gas will be zero
A gas at certain temperature and volume has a pressure equal to 75 cm of Hg. If the mass of the gas is doubled, at the same volume and same temperature, its new pressure will be
A marble block of mass 2 kg lying on ice when given a velocity of 6 m−s⁻1 is stopped by friction in 10 s. Then the coefficient of friction is (Take g = 10 m−s⁻2)
300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g = 10 m/s2, work done against friction is
A capillary tube of radius r is immersed in water and water rise in it to a height h. Mass of water in capillary tube is m. If the radius of the tube is doubled, the mass of water that will rise in capillary will be
A capillary tube when immersed vertically in a liquid records a rise of 3 mm. If the tube is immersed in the liquid at an angle of 60” with the vertical, then height of the liquid in the capillary tube will be
Two water pipes P and Q having diameters 2 cm and 4 cm respectively are joined in series with the main supply line of water. The velocity of water flowering in pipe P is
A spherical drop of water has 1 mm radius. If the surface tension of water is 70x10⁻3 N-m⁻1, then difference of pressures between inside and outside of spherical drop is
Spherical balls of radius R are falling in a viscous fluid of viscosity η with a velocity v. The retarding viscous force acting on the spherical ball is:
The extension in a string, obeying the Hooke's law, is x. The speed of sound in the stretched string is v. If the string is extended to 1.5 x, then speed of sound will be
A wire fixed at the upper end, stretches by length l by applying a force F. Work done in stretching done the wire is
The path of a particle moving under the influence of a force fixed in magnitude and direction is
A body is whirled in a horizontal circle of radius 20 cm. It has angular velocity of 10 rad/s. What is its linear velocity at any point on circular path
The magnifying power of a telescope is 'm'. If the focal length of the objective is doubled, then its magnifying power will become