# Physics Questions for Railway ALP Stage-II Exam : 14th December 2018

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Q1. Damp clothes are dried in spin dryers by the action of
स्पिन ड्रायर में गीले कपड़ों को सूख किस प्रक्रिया द्वारा सुखाया जाता हैं?
(a) centripetal forces / अभिकेन्द्रीय बल
(b) centrifugal forces/ अपकेन्द्रीय बल
(c) central forces/ केन्द्रीय बल
(d) non-central forces/ गैर केंद्रीय बल

Ans.(b)
Sol. Centrifugal force is an outward force apparent in a rotating reference frame. It does not exist when a system is described relative to an inertial frame of reference. Damp clothes are dried in spin dryers by the action of centrifugal forces.

Q2. The atmospheric air is held to the earth by
वायुमंडलीय हवा पृथ्वी पर किस के कारण बनी रहती है?
(a) gravity/ गुरुत्वाकर्षण
(b) winds/ हवा
(c) clouds/ बादल
(d) rotationn of the Earth/ पृथ्वी के घूर्णन

Ans.(a)
Sol. The atmospheric air is held to the earth by the force of gravity which holds down the atmosphere. The atmospheric air molecules cannot escape the gravitational pull of the Earth as the escape velocity on the Earth’s surface is 11.2 km/s. At the moon’s surface the value of escape velocity is 2.38 km/s so there is no any atmosphere around the moon.

Q3. The minimum number of geostationary satellites needed for uninterrupted global coverage is
निर्बाध वैश्विक कवरेज के लिए भू-स्थिर उपग्रहों की कितनी न्यूनतम संख्या आवश्यक है?
(a) 3
(b) 2
(c) 4
(d) 1

Ans.(a)
Sol. Minimum three geostationary satellites are needed for the uninterrupted global coverage.

Q4. We always see the same face of the moon, because
हम चाँद का हमेशा एक ही चेहरा देखते हैं, क्योंकि
(a) it is smaller than the Earth/ यह पृथ्वी से छोटा है
(b) it revolves on its axis in a direction opposite to that of the Earth/ यह पृथ्वी के विपरीत दिशा में अपनी धुरी पर घूमता है
(c) it takes equal time for revolution around the Earth and rotation on its own axis / पृथ्वी के चारों ओर क्रांति और अपने अक्ष पर घूर्णन के लिए बराबर समय लगता है
(d) it rotates at the same speed as the Earth around the Sun/ यह सूर्य के चारों ओर पृथ्वी के समान गति से घूमता है

Ans.(c)Sol. The synchronous rotation causes the moon to be present just one side to the earth all the time.
This synchronous rotation is the result of tidal locking which occurs when the gravitational gradient makes one side of an astronomical body always face another.
A tidally locked body takes just as long to rotate around its own axis as it does to revolve around its partner. This causes one hemisphere constantly to face the partner’s body.

Q5. What changes will happen to a bowl of ice and water kept at exactly zero degree Celsius?
यदि एक बर्फ के कटोरे और पानी के कटोरे को शून्य डिग्री सेल्सियस पर रखा जाता है तो क्या परिवर्तन होगा?
(a) All ice will melt/सभी बर्फ पिघल जाएगी
(b) All water will become ice/सभी पानी बर्फ बन जाएगा
(c) No change will happen/कोई परिवर्तन नहीं होगा
(d) Only some ice will melt/केवल कुछ बर्फ पिघलेगी

Ans.(c)
Sol. Zero degree celsius is called the freezing point of water at which the mixture of fresh water and ice has an equilibrium temperature.
When heat is added to the mixture ice starts melting but when heat is removed water starts freezing. Thus, no any change would be observed when the bowl of ice and water is kept at exactly zero degree celsius.

Q6.Heat transfer horizontally within the atmosphere is called
वायुमंडल के भीतर क्षैतिज रूप से हीट ट्रांसफर को क्या कहा जाता है?
(a) conduction/ संचालन
(b) convection/ संवहन
(c) absorption/ अवशोषण

Ans.(d)
Sol. The horizontal transfer of heat by the wind is called the process of advection which is a transport mechanism of the substance. It is the property of a fluid due to its bulk motion. The transport of pollutant or silt in the river by means of bulk water flow downstream is an example of advection.

Q7. What happens to a liquid when the vapour pressure equals the atmospheric pressure?
जब वाष्प दबाव और वायुमंडलीय दबाव बराबर होता है तो तरल का क्या होता है?
(a) The liquid cools/ तरल ठंडा हो जाता है
(b) The liquid boils/ तरल उबल जाता है
(c) No change/ कोई परिवर्तन नहीं होता है
(d) The liquid evaporates/ तरल का वाष्पीकरण हो जाता है
Ans.(b)
Sol. When the vapour pressure equals the atmospheric pressure, the liquid starts boiling as the vapour pressure being low and since the pressure inside the liquid is equal to atmospheric pressure the bubbles of water vapour cannot boil. At the boiling point, the saturated vapour pressure is equal to the atmospheric pressure and the bubbles form.

Q8. Indicate the false statement about the resistance of a wire
तार के प्रतिरोध के बारे में इनमें से कौन सा कथन गलत है?
(a) It depend on material of wire/ यह तार के सामग्री पर निर्भर करता है
(b) It is unrectly proportional to the length of wire/ यह स्वतंत्र रूप से तार की लंबाई के साथ आनुपातिक है
(c) It is directly proportional to the area of cross-section of wire/ यह तार के क्रॉस-सेक्शन के क्षेत्रफल से सीधे आनुपातिक है
(d) Resistance of metallic wire increases with increase in temperature / तापमान में वृद्धि के साथ धातु के तार का प्रतिरोध बढ़ता है
Ans.(c)
Sol. The resistance of a current carrying conductor is inversely proportional to the area of cross section of the conductor. The reason is because the resistance occurs due to the collision of electrons/charged particles.So resistance is inversely proportional to area of cross section of the conductor.

Q9.For which of the following substances, the resistance decreases with increase in temperature?
निम्नलिखित पदार्थों में से किसके तापमान में वृद्धि के साथ प्रतिरोध कम हो जाता है?
(a) Pure silicon/ शुद्ध सिलिकॉन
(b) Copper/ तांबा
(c) Nichrome/ निक्रोम
(d) Platinum/ प्लैटिनम
Ans.(a)
Sol. Pure Silicon at room temperature has perhaps one conduction electron for every 1013 (that’s ten trillion) atoms. Increasing the temperature of intrinsic semiconductors provides more thermal energy for electrons to absorb, and thus will increase the number of conduction electrons. Voila – decreased resistance.

Q10. The ratio of intensity of magnetisation to the magnetisation force is known as
चुंबकत्व की तीव्रता का चुंबकत्व बल से अनुपात को किस रूप में जाना जाता है?
(a) flux density / फ्लक्स घनत्व
(b) susceptibility / संवेदनशीलता
(c) relative permeability / तुलनात्मक भेद्दता
(d) none of the above/इनमें से कोई नहीं
Ans.(b)
Sol. In electromagnetism, the magnetic susceptibility is one measure of the magnetic properties of a material. The susceptibility indicates whether a material is attracted into or repelled out of a magnetic field.

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