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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
ماحولیاتی تحفظ کی ایجنسیاں کلورو فلورو کاربن ریفریجریٹ کے استعمال کے خلاف مشورہ دیتی ہیں کیوں کہ یہ _____ کے ساتھ رد عمل ظاہر کرتے ہیں؟
- Ozone layer
- Water vapour and cause acid rain
- Plastic and cause green
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Chloro-fluoro carbon (CFC) refrigerants react with and destroy the ozone layer, which protects Earth from harmful UV radiation.
This depletion leads to increased UV exposure, causing health and environmental hazards.
CFCs have been largely replaced by HFCs and other eco-friendly refrigerants to reduce ozone damage.
کے مقصد کو پورا کرنے کے لئے ایک چھوٹی سی ریفریجریٹر میں ایک کیپلیری ٹیوب استعمال کی جاتی ہے؟ _____
- Evaporator
- Thermostat
- Expansion valve
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
A capillary tube in a small refrigerator acts as an expansion valve, controlling the flow of refrigerant into the evaporator.
It reduces the pressure of the liquid refrigerant, causing it to expand and cool in the evaporator.
The capillary tube is simple, inexpensive, and has no moving parts, making it ideal for small refrigeration systems.
جب کسی گھڑی کا موسم بہار زخمی ہوجاتا ہے تو ، اس کا _____ ہوگا؟
- Electrical energy
- Strain energy
- Kinetic energy
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Winding the spring of a watch stores strain energy in the spring due to deformation.
This energy is then gradually converted into kinetic energy to drive the watch mechanism.
Strain energy is a form of potential energy stored in elastic objects when twisted or stretched.
کسی ندی کے بہاؤ کی شرح کا تعین ______ کے ذریعہ کیا جاسکتا ہے؟
- Weir
- Kennison nozzle
- Kundt’s tube
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
A weir is a barrier across a river used to measure the flow rate of water by observing the water height over it.
The flow rate can be calculated using empirical formulas based on the weir type and head of water.
Weirs are widely used in hydrology and water resource management for river discharge measurements.
مطلق صفر درجہ حرارت سے بالاتر تمام جسم تابکاری کا اخراج کرتے ہیں۔ مذکورہ بالا بیان ______ پر مبنی ہے؟
- Wien’s law
- Provost theory
- Plank’s law
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Prevost’s theory of heat exchange states that all bodies above absolute zero continuously emit and absorb radiation.
The net heat exchange depends on the difference between emitted and absorbed radiation.
At thermal equilibrium, the rate of emission equals the rate of absorption.
دھند کی تشکیل _____ کی وجہ سے ہے؟
- Temperature falls of atmosphere
- High pressure
- Humidity
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Fog forms when the atmospheric temperature falls to the dew point, causing water vapor to condense into tiny droplets.
This usually happens during cool, calm conditions, especially at night.
High humidity helps fog formation, but the primary cause is the fall in temperature.
گرمی کو موصل پائپ سے آس پاس کی ہوا میں منتقل کیا جاتا ہے بنیادی طور پر ______ کے ذریعہ؟
- Radiation
- Conduction
- Free convection
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Around an insulated pipe, heat reaches the surrounding still air mainly through natural (free) convection due to density differences in air.
Since the air is still, there is no forced movement to cause forced convection.
Radiation may also occur, but free convection is the dominant mode in this case.
تھرمل چالکتا کی اعلی قیمت ______ کے لئے متوقع ہے؟
- Boiling water
- Solid ice
- Melting ice
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Solid ice has a more ordered structure, allowing heat to transfer more efficiently than in liquid water.
Therefore, its thermal conductivity is higher than that of water or boiling water.
During melting, energy is used for phase change rather than heat transfer, so thermal conductivity is lower than solid ice.
سطح کی گیج ______ کے لئے استعمال ہوتی ہے؟
- Check the surface finish
- Layout the work accurately
- Level the surface plate
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
A surface gauge is used to mark and lay out lines on workpieces with high accuracy.
It helps in checking parallelism and transferring measurements from a reference surface.
Surface gauges are commonly used along with a surface plate for precision marking work.
- Absorptivity as well as transmissivity
- Absorptivity
- Reflectivity
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
Gases have poor absorptivity, meaning they absorb very little radiant heat.
Most gases are nearly transparent to radiation, so absorption is minimal.
Because of poor absorptivity, gases also have low emissivity, but high transmissivity.
