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A black body is at temperature o 500 K. it emits energy rate which is proportional to
According to Stefan's law, energy emitted
The speed of a car moving on a straight road becomes 50 km/hr from 20 km/hr in 10 seconds. The acceleration of the car is—
If the number of rotations of earth increases, then the weight of the objects on its surface—
The centripetal force required for the circular motion is obtained by the weight of the object. Similarly, the centripetal acceleration required for the circular motion is obtained by the gravitational acceleration, when the object exhibiting circular motion is situated on earth’s surface. In this way the effective gravitational acceleration (g’) of the particle in circular motion will be—
Where, r is the radius of the circular path, ω is the angular velocity. From the above relation it is clear that g’ will decrease with increase in ω. Therefore, the weight of an object will decrease.
Red is used an as emergency or danger signal as
Red is used as an emergency or danger signal as its wavelength is the longest of the entirecolor and is able to travel the longest distance through fog, rain etc.
The speed of light with the rise in the temperature of the medium
The speed of light with the rise in the temperature of the median remains unaltered as the speed of light is independent of the temperature of the medium.
Five resistances of 10 ohm each are connected as shown in fig.
The equivalent resistance between A and C will be—
In a balanced Wheatstone bridge the points B and D are at the same potential. When battery is connected between A and C no current flows through BD. Therefore, the 10 ohm resistance of BD is ineffective. Therefore, resistance of ABC
= 20 ohm
Resistance of ADC = 10+10
Both are joined in parallel therefore, if their equivalent resistance is R. then
Tungsten is used for the manufacture of the filament of an electric bulb, because
Tungsten has a very high melting point (3422ᵒC).
The material used in the fabrication of a transistor is
A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. Silicon is a semiconductor material which is mostly used in the fabrication of the transistor.
Sound travels in the form of
Sound travels in the form of longitudinal waves. These waves travel in the form of compressions and rarefactions.
The speed of light will be minimum while passing through-
Any of the object or material which has the highest refractive index has the minimum speed of light. The glass has the highest refractive index among other like, vacuum, water and air.
The radius of curvature of the plane mirror is:
The radius of curvature of the plane is infinity.
Which one of the following is the best conductor of electricity?
Electrical conductivity is a measure of the amount of electrical current under a material can carry. The most electrically conductive element is silver.
Which is not used as Atomic fuel?
The most common nuclear fuels are uranium – 235 (235U) and plutonium -239(239Pu). Thorium is more abundant in nature than uranium. Thorium can be used as a nuclear fuel through breeding to uranium-233 (U-233). Lead is not used as a nuclear fuel.
The gas used in discharge tubes for optical decoration and advertising is-
The neon gas is used in discharge lamps, tubes and in fluorescent bulbs.
Which one of the following pairs is not correctly matched:
In 1935 Meson particles were discovered by Japanese physicist Hideki Yukawa. Positron, the antiparticle of the antimatter counterpart of the electron was discovered by C.D. Anderson and U.F. Hess in 1932. In 1939, Hans Bethe described the nuclear reactions that power the sun and other starts. In the synthesis of transuranic elements, Glenn T. Scaborg played an important role instead of Enrico Fermi. The fact is that he attempted to prepare a transuranium element in 1934 in Rome but failed to do so.
The maximum density of water is at
The density of water increases with temperature but volume decreases. At 4°C, the volume of water is low and density is maximum. Conversion of Celsius in Kelvin
K = C + 273
= 4 + 273 = 277
So, the density of water is maximum at 277 K.
The technique to integrate and mark the image of a three- the Dimensional object is-
Holography is a technique of producing a three-dimensional image of an object.
Which type of electromagnetic radiation is used in the remote control of a television receiver?
Most remote controls of a television receiver send signals using Infra-red radiation.
Which one of the following is not correct:
Option (b) is not correct. It is because the breaking apart of nucleus of an atom is called fission not fusion. Fission is a radioactive decay process in which the nucleus of an atom splits into smaller parts.