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Q:

# For accurate scientific work, temperatures are often measured by

 A) mercury thermometers B) alcohol thermometers C) platinum resistance thermometers D) thermoelectric thermometers

Answer:   C) platinum resistance thermometers

Explanation:

The resistance of metallic conductors e.g, platinum, increases with rise of  temperature . The increase in temperature results in a decrease of current which can be recorded in a galvanometer if the conductor is included in an electrical circuit. Thus the temperature can be known; platinum resistance thermometer is used generally for accurate scientific work. When two dissimilar metals are joined at the ends, and these ends are subjected to a difference of temperature, a current flows through the metals. Greater the difference of temperature , greater the current. So the curent strength can form the basis for measuring the difference in temperature. And when one of these temperatures is known, we can calculate the other.

Subject: Physics
Q:

Two metallic plate of equal thickness and coefficient thermal conductivity K1 and K2 put together face to face. A common plate is constructed. What is equivalent K?

 A) K1k2/k1+k2 B) 2k1k2/k1+k2 C) K1+k2/k1k2 D) None

Explanation:

We know that,

The equivalent K =  $\fn_jvn \small \frac{L1+L2}{\frac{L1}{K1}+\frac{L2}{K2}}$

where L1 & L2 are plate1 & Plate2 thicknesses, K1 & K2 are coefficient thermal conductivity of plate1 & Plate2 respectively.

But here L1 = L2 = L (say)

Then K = L+L/(L/K1 + L/K2)  =  $\fn_jvn \small \frac{2K1K2}{K1+K2}$

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4 89
Q:

"Light years" is the unit of _____?

 A) Acceleration B) Distance C) Light Intensity D) Weight

Explanation:

A Light-year is a distance that light travels in the vacuum in one Julian year (365.25 days).

The light-year is a unit of length used to express astronomical distances. It is about 9.5 trillion kilometers or 5.9 trillion miles.

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6 176
Q:

"The Law of Kepler" is related with which among the following ?

 A) Planetary Motion B) Law of Conservation of energy C) Law of Gravitation D) None

Answer & Explanation Answer: A) Planetary Motion

Explanation:

Kepler's laws of planetary motion are three scientific laws describing the motion of planets around the Sun.

• Kepler’s three laws of planetary motion can be stated as follows:

(1) All planets move about the Sun in elliptical orbits, having the Sun as one of the foci.

(2) A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time.

(3) The squares of the sidereal periods (of revolution) of the planets are directly proportional to the cubes of their mean distances from the Sun.

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10 135
Q:

The Hydraulic Break works on the principle of _____ ?

 A) Pascal's Law B) Boyle's law C) Coulomb's law D) Bernouli's law

Answer & Explanation Answer: A) Pascal's Law

Explanation:

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6 304
Q:

What is the full form of "RADAR" ?

 A) Radio Detecting and Ranging B) Region Device and Ranging C) Radio Detect and Rangs D) Radio Device and Ranging