JEE Main Properties of Matter & Heat – Topic Test

Topics in this test

Difficulty: 15 medium · 15 hard

Properties of Matter & Heat MCQ questions with answers

The first 3 of 30 questions. Unlock the series for the rest, each with a solution.

1. Q1. In one complete cycle, a system absorbs 800 J of heat during one part of the cycle and rejects 500 J during the remainder. The net work done by the system per cycle is:

   एक पूर्ण चक्र में, एक निकाय चक्र के एक भाग के दौरान 800 J ऊष्मा अवशोषित करता है और शेष भाग के दौरान 500 J निष्कासित करता है। निकाय द्वारा प्रति चक्र किया गया नेट कार्य है:

   • A. 1300 J
   • B. 500 J
   • C. 300 J
   • D. zero / शून्य
   Solution

   Over a complete cycle the internal energy change is zero, so the net work equals the net heat: W = 800 − 500 = 300 J.

   पूर्ण चक्र में आंतरिक ऊर्जा में परिवर्तन शून्य होता है, अतः नेट कार्य नेट ऊष्मा के बराबर होता है: W = 800 − 500 = 300 J।

2. Q2. A Carnot engine operates between a source at 800 K and a sink at 300 K. The maximum possible efficiency of the engine is:

   एक कार्नो इंजन 800 K के स्रोत और 300 K के सिंक के बीच कार्य करता है। इंजन की अधिकतम संभव दक्षता है:

   • A. 50%
   • B. 25%
   • C. 62.5%
   • D. 37.5%
   Solution

   Carnot efficiency η = 1 − T_c/T_h = 1 − 300/800 = 0.625 = 62.5%.

   कार्नो दक्षता η = 1 − T_c/T_h = 1 − 300/800 = 0.625 = 62.5%।

3. Q3. The efficiency of a Carnot engine can be exactly 100% only when:

   कार्नो इंजन की दक्षता ठीक 100% केवल तभी हो सकती है जब:

   • A. the sink is at 0°C / सिंक 0°C पर हो
   • B. the sink is at absolute zero temperature / सिंक परम शून्य ताप पर हो
   • C. the working substance is a monatomic ideal gas / कार्यकारी पदार्थ एकपरमाणुक आदर्श गैस हो
   • D. the source and sink are at the same temperature / स्रोत और सिंक समान ताप पर हों
   Solution

   Since η = 1 − T₂/T₁, the efficiency equals unity only if the sink temperature T₂ is absolute zero, which is unattainable; hence no real engine can be 100% efficient.

   चूँकि η = 1 − T₂/T₁, दक्षता इकाई के बराबर केवल तभी होगी जब सिंक का ताप T₂ परम शून्य हो, जो अप्राप्य है; अतः कोई भी वास्तविक इंजन 100% दक्ष नहीं हो सकता।

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