Physics Questions And Answers 140-153

140. Radioactivity was discovered by_________?
 A. J.J. Thomson
 b.  W.Roentgen
 c.  H.Becquerel
 d.  None of these

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Ans. C H. Becquerel
Antoine-Henri Becquerel is known for his discovery of radioactivity, for which he received the Nobel Prize for Physics in 1903 Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. The decomposition process is called radioactivity.



141. Acceleration is _____
a. The speed at any given instant in time
b. The rate at which an object moves
c. The rate at which an object changes its velocity
d. None of the above

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ANSWER: c. The rate at which an object changes its velocity



142. When the electron of hydrogen atom jumps from any of the outer orbits to the first orbit, the series of spectral lines emitted is called
a. Balmer series
b. Paschen series
c. Brackett series
d. Lyman series

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ANSWER : : Lyman series



143. Water is a _____________ Conductor of electricity.  
A.  super conductor
B.  bad conductor
C.  speed conductor
D.  None of these

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Answer : B.  bad conductor




144. By which of the following methods does heat transfer not take place?   
a. Convection
b. Refraction Right!
c. Conduction
d. Radiation

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Answer : B


145. Which one of the following is an scalar quantity?
A.  Force
B.  Pressure
C.  Velocity
D.  Acceleration

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Answer : B.  Pressure


146. When a body moves with a constant speed in a circle?
a.   its acceleration is zero
b.   its acceleration is increasing
c.   its velocity is uniform
d.   its velocity is changing


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Answer : its velocity is changing



147. A thermometer for measuring very low temperature is called: 
a. pyrometer
b. bolometer
c. cryometer
d. platinum resistant thermometer

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Answer : c. cryometer


148.   Which Instrument is used to determine the intensity of colors?
A. Chronometer                               
B. Cathetometer              
C. Colorimeter                   
D. Commutator

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Ans. C




149. Newton's 1st Law is the law of -
1. Inertia
2. Force
3. Momentum
4. Acceleration

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Ans: 1



150. Name of the instrument to measure atomspheric pressure ?
a. Barometer
b. Barograph
c. Bolometer
d. Callipers

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Answer: Option A
Explanation:
Barograph - Recordings of atmospheric pressure,
Bolometer - Used to measure heat radiation,
Callipers - Used to measure inner and outer diameters of bodies.




151. Aviation fuel for Jet aeroplanes consists of purified  
A.  Petrol
B.  Kerosene
C.  Gasoline
D.  Diesel

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Answer : B.  Kerosene



152.  Large transformers, when used for some time, become very hot and are cooled by circulating oil. The heating of the 
transformer is due to
A. the heating effect of current alone
B. hysteresis loss alone
C. both the heating effect of current and hysteresis loss
D. intense sunlight at noon

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Answer: C




153. The base of an electric iron is brightly polished mainly
A) to make it smooth and frictionless
B) to make it rust-proof
C) to reduce heat loss by radiation
D) to make it more durable

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Answer: C) to reduce heat loss by radiation 
Explanation:
Polished surfaces are poor radiators of heat. So loss of heat on that account is reduced and the electric iron remains 
hotter than otherwise.



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