Physics (Part-II) (Railway)

Total Questions: 50

11. Which of the following statements is true? [RRB ALP & Technician Exam, 20.08.2018 Shift-III]

The velocity of sound is:

(1) less in summer than in winter
(2) same in winter and summer
(3) independent of seasons
(4) more in summer than in winter

Correct Answer: (4) more in summer than in winter

Solution:The speed of sound in a medium depends on temperature of the medium. As the temperature of medium increases, the particles of medium collide more frequently and hence the disturbance spread faster. That is the reason sound travels faster in summer than in winter.

12. What is the upward force exerted by water called? [RRB ALP & Technician Exam, 21.08.2018 Shift-I]

(1) Gravitation
(2) Density
(3) Buoyant force
(4) Friction

Correct Answer: (3) Buoyant force

Solution:Buoyancy or upthrust is an upward force exerted by a fluid that opposes the weight of an immersed object.It is caused by differences in pressure acting on opposite sides of an object immersed in a static fluid. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the volume of the object, i.e. the displaced fluid.

13. If the resistance of a conductor is reduced to half its initial value, then the heating effect in the conductor will become________. [(RRB ALP & Technician Exam, 21.08.2018 Shift-I]

(1) one-fourth
(2) half
(3) double
(4) four-times

Correct Answer: (2) half

Solution:Heating effect of electric current I, through a conductor of resistance, R for a time, t is given by H = I² Rt. This equation is called the Joule's equation of electrical heating. So, resistance is directly proportional to the heating effect in a conductor. This implies that when resistance is reduced to half its initial value, then heating effect will become half as well.

14. A conductor having some appreciable resistance is called a: [RRB ALP & Technician Exam, 21.08.2018 Shift-I]

(1) Conductor
(2) Insulator
(3) Resistor
(4) Semi-conductor

Correct Answer: (3) Resistor

Solution:Motion of electrons through a conductor is retarded by its resistance. A component of a given size that offers a low resistance is a good conductor. A conductor having some appreciable resistance is called a resistor. A component of identical size that offers a higher resistance is a poor conductor. An insulator of the same size offers even higher resistance.

15. A unit of power is called a: [RRB ALP & Technician Exam, 21.08.2018 Shift-l]

(1) Watt
(2) Joule
(3) Newton
(4) Pascal

Correct Answer: (1) Watt

Solution:Watt (W) is the unit of power. One watt is defined as the energy consumption rate of one joule per second. IW = IJ/Is. It is also defined as the current flow of one ampere with voltage of one volt. The watt unit is named after James Watt, the inventor of the steam engine.

16. In a concave mirror when the object is placed at infinity which of the following applies to the image? [RRB ALP & Technician Exam, 21.08.2018 Shift-l]

(1) Real, inverted image of the same size at centre of curvature (C)
(2) Real, Inverted, highly diminished image at focus
(3) Real, inverted, highly enlarged image at centre of curvature (C)
(4) Real, Inverted, diminished image between centre of curvature (C) and principal focus (F)

Correct Answer: (2) Real, Inverted, highly diminished image at focus

Solution:In the case of a concave mirror, when the object is placed at infinity, the two rays running parallel to the principal axis get reflected and intersect each other at the principal focus F on the principal axis. Therefore, in this case the image is formed at the principal focus which is highly diminished, real and inverted.

17. Work done by an object on application of a force would be zero if the displacement of the object is: [RRB ALP & Technician Exam, 21.08.2018 Shift-III]

(1) Negative
(2) Positive
(3) Neutral
(4) Zero

Correct Answer: (4) Zero

Solution:Work is done only when a certain force is applied on an object and the object moves a certain distance on the direction of the applied force. Work done is zero when dis placement is zero.

18. Echoes may be heard more than once due to successive or multiple: [RRB ALP & Technician Exam, 21.08.2018 Shift-III]

(1) Rarefactions
(2) Reflections
(3) Diffractions
(4) Refractions

Correct Answer: (2) Reflections

Solution:Echoes may be heard more than once due to repeated or multiple reflections of sound from several reflecting surfaces. When sound, or the echo Itself, is reflected multiple times from multiple surfaces, the echo is characterized as a reverberation.

19. If V/I is a constant, it is called: [RRB ALP & Technician Exam, 21.08.2018 Shift-III]

(1) Potential difference
(2) Current
(3) Coulomb
(4) Resistance

Correct Answer: (4) Resistance

Solution:The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current which flows through it: If the resistance is constant over a considerable range of voltage, then Ohm's law, I = V/R, can be used to predict the behavior of the material.

20. The formula of Power is: [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) mormentum/time
(2) work/time
(3) speed/time
(4) displacement/time

Correct Answer: (2) work/time

Solution:In physics, power is the rate of doing work or transferring heat, the amount of energy transferred or converted per unit time. Being the rate of work, the equation for power can be written as:

Power = Work/Time. In the International System of Units, the unit of power is the joule per second (J/s), known as the watts (W) in honour of James Watt.

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