PST PAST PAPER 25-09-2021
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
ستارہ آخرکار زیادہ گھنا اور گرم ہو کر ہیلیم میں کس عمل کے ذریعے تبدیل ہوتا ہے؟
- Nuclear fusion
- Nuclear Fission
- Radioactive decay
- Chemical reaction
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Stars produce energy by combining lighter nuclei into heavier nuclei in their cores.
- In the core of a star, hydrogen nuclei fuse to form helium.
- This process releases a huge amount of energy in the form of light and heat.
- It is the primary source of a star’s energy and sustains its radiation for billions of years.
Last verified on 17-03-2026
پتے میں پتلی رگیں کس چیز کی نقل و حمل کے لیے موجود ہیں؟
- Oxygen
- Carbon Dioxide
- Food
- Minerals
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Leaves have thin veins called vascular bundles.
- Veins consist of xylem and phloem for transport.
- Xylem transports water and minerals from roots to leaves.
- Phloem transports food (sugars) from leaves to other parts of the plant.
Last verified on 17-03-2026
پودوں کی صحت مند نشوونما کے لئے درکار تین ضروری عناصر _____ ہیں؟
- Carbon (C), Oxygen (O), and Hydrogen (H)
- Phosphorus (P), Potassium (K), and Nitrogen (N)
- Helium (He), Neon (Ne), and Argon (Ar)
- Calcium (Ca), Magnesium (Mg), and Sulfur (S)
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Phosphorus (P), Potassium (K), and Nitrogen (N) are three essential macronutrients for plant growth.
- It is also referred to as "NPK".
- They play critical roles in various plant processes, including photosynthesis, root development, and cell growth.
Last verified on 17-03-2026
مندرجہ ذیل میں سے کون سا بیان سرکٹ کے بارے میں درست ہے؟
- Parallel and the current flows clockwise
- Series and the current flows clockwise
- Series and the current flows counterclockwise
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- In a series circuit, components are connected one after another in a single path.
- The current is the same through all components.
- Conventional current flows from positive to negative, typically clockwise in diagrams.
- Parallel circuits have multiple paths, unlike series circuits.
Last verified on 17-03-2026
ایک مقناطیس جس کو مقناطیس کرنا مشکل ہے ______ کہلاتا ہے؟
- Permanent magnet
- Temporary Magnet
- Electromagnet
- None of these
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Explanation
- A permanent magnet retains its magnetism for a long time.
- It is hard to magnetize but difficult to demagnetize once magnetized.
- Made from hard magnetic materials like steel or alnico.
- Unlike temporary magnets, it does not lose its magnetism easily.
Last verified on 17-03-2026
لہر کی رفتار ______ کے برابر ہے؟
- Wavelength x Frequency
- Wavelength / Frequency
- Frequency / Wavelength
- Wavelength + Frequency
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- The velocity of a wave depends on its wavelength and frequency.
- Formula: v = λ × f, where λ is wavelength and f is frequency.
- This applies to sound waves, light waves, and water waves.
- Higher frequency or longer wavelength increases the wave’s velocity if the medium is constant.
Last verified on 17-03-2026
- Repeating sounds
- Refracted sounds
- Absorbed sounds
- Amplified sounds
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- An echo is a sound that reflects off a surface and is heard again.
- It occurs when sound waves bounce back from a distant surface like a wall or mountain.
- Echoes are common in caves, valleys, and empty halls.
- The reflected sound is perceived after a short delay.
Last verified on 17-03-2026
کشش ثقل پر قابو پانے کے لیے کس چیز کی ضرورت ہوتی ہے؟
- Gravitational force
- Friction
- Mass
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Gravity pulls objects toward the center of the Earth.
- To lift or move an object against gravity, a force equal to or greater than gravitational force is needed.
- This force allows objects to rise or stay in motion vertically.
Last verified on 17-03-2026
اگر ہم مارکر کو ہاتھ میں پکڑ کر چھوڑ دیں تو کیا ہوگا؟
- The force upward is shorter than the force downward
- The force upward is greater than the force downward
- Resultant force is maximum
- None of these
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- When a marker is held and released, gravity pulls it downward.
- If there was an initial upward push, the upward force can be greater than the downward force momentarily.
- The marker accelerates until gravity slows it and pulls it back down.
- This explains the initial upward motion before falling.
Last verified on 17-03-2026
جب روشنی ____ سے داخل ہوتی ہے تو روشنی کا مکمل اندرونی انعکاس ممکن ہے؟
- Air to water
- Glass to glass
- Water to air
- Air to glass
اس سوال کو وضاحت کے ساتھ پڑھیں
Explanation
- Total internal reflection occurs when light travels from a denser medium to a rarer medium.
- The angle of incidence must be greater than the critical angle for the two media.
- Light is completely reflected back into the denser medium instead of refracting.
- Common examples: optical fibers, diamonds, and mirages.
Last verified on 17-03-2026
