SPSC PHYSICS 25 YEARS PAST PAPERS
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
- Number of electrons increases while that of holes decreases
- Number of holes increases while that of electrons decreases
- Number of electrons and holes remain same
- Number of electron and holes increases equally
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Explanation
- When an N-type semiconductor is heated, thermal energy generates electron–hole pairs.
- The number of electrons increases in the conduction band.
- At the same time, equal number of holes are created in the valence band.
- Doping does not change this thermal generation behavior.
Last verified on 05-06-2026
جب ایک الیکٹرک ڈائپول پر الیکٹرک فیلڈ ٹارک پیدا کرتا ہے تو یہ کس حالت میں ہوتا ہے؟
- The field is parallel to the dipole moment
- The field is negative
- The field is perpendicular to the dipole moment
- The field is positive
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Explanation
- A torque acts on an electric dipole in an external electric field.
- Torque depends on the angle between dipole moment and electric field.
- Maximum torque occurs when the field is perpendicular to the dipole moment.
- If the field is parallel, torque becomes zero.
Last verified on 05-06-2026
مندرجہ ذیل میں سے کس حالت میں نیٹ الیکٹرک فیلڈ صفر ہوتا ہے؟
- Inside any conductor
- Inside any conductor with a static charge
- Inside any material, conductor or insulator, with a static charge
- The electric field cannot be zero
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Explanation
- Net electric field inside a conductor in electrostatic equilibrium is zero.
- Free electrons in a conductor rearrange themselves until internal field cancels out.
- This condition holds when the conductor is in a static (electrostatic) state.
- Inside insulators, electric field is generally not zero.
Last verified on 05-06-2026
الفا پارٹیکل کی وہ اوسط دوری جو وہ ہوا میں طے کرتا ہے جب تک اس کی آئنائزنگ طاقت ختم نہ ہو جائے، اسے کیا کہتے ہیں؟
- Trajectory
- Range
- Firing level
- Limit
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Explanation
- The average distance covered by an alpha particle in air before losing its ionizing power is called its range.
- Alpha particles lose energy continuously while moving through air.
- They stop ionizing after traveling a certain distance.
- This stopping distance is not straight-line path always due to collisions.
Last verified on 05-06-2026
نیوکلیئر ری ایکٹر میں مندرجہ ذیل میں سے کون سا صحیح بیان ہے؟
- Moderator slow down the neutron
- Moderator bring the neutrons to rest
- Moderator absorb the neutron
- Moderator reflect the neutron
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Explanation
- In a nuclear reactor, a moderator slows down fast neutrons.
- Slow (thermal) neutrons are more effective in sustaining fission.
- Moderators do not stop, absorb, or reflect neutrons completely.
- Common moderators are graphite and heavy water.
Last verified on 05-06-2026
ہائیڈروجن اسپیکٹرم کی کون سی سیریز الٹرا وائلٹ ریجن میں پائی جاتی ہے؟
- Lyman series
- Balmer series
- Paschen series
- Bracket series
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Explanation
- Lyman series lies in the ultraviolet (UV) region of hydrogen spectrum.
- It is produced when an electron falls to the first energy level (n = 1).
- These transitions release high-energy photons.
Additional information:
- Balmer series lies in the visible region.
- Paschen and Brackett are in infrared.
Last verified on 05-06-2026
جب مناسب فریکوئنسی کی روشنی دھات کی سطح پر پڑتی ہے تو الیکٹران خارج ہوتے ہیں، اس عمل کو کیا کہتے ہیں؟
- X-ray emission
- Compton effect
- Nuclear fission
- Photoelectric effect
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Explanation
- Photoelectric effect is the phenomenon where electrons are ejected from a metal surface.
- It occurs when light of suitable frequency falls on the metal.
- The incident photons transfer energy to electrons.
- If energy is sufficient, electrons are emitted from the surface.
Last verified on 05-06-2026
اینٹروپی میں اضافہ کس چیز کے بڑھنے کے برابر ہوتا ہے؟
- Disorder
- Unavailability of energy
- Randomness
- All of these
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Explanation
- Entropy is a measure of disorder in a system.
- Increase in entropy means increase in randomness of particles.
- It also means energy becomes less available for useful work.
Last verified on 05-06-2026
صابن کی جھلی سورج کی روشنی میں خوبصورت رنگ کیوں دکھاتی ہے؟
- Dispersion of light
- Interference of light
- Diffraction of light
- Scattering of light
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Explanation
- Soap film shows brilliant colors due to interference of light.
- Light waves reflect from the top and bottom surfaces of the thin film.
- These reflected waves interfere with each other.
- Constructive and destructive interference produce different colors.
Last verified on 05-06-2026
پروجیکٹائل موشن کے دوران افقی رفتار کا جزو کیا ہوتا ہے؟
- Changes with time
- Becomes zero
- Remains constant
- Increases with time
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Explanation
- In projectile motion, horizontal velocity has no acceleration.
- No force acts in the horizontal direction (ignoring air resistance).
- Therefore, horizontal velocity does not change with time.
- Only vertical velocity changes due to gravity.
- So, horizontal component remains constant.
Last verified on 05-06-2026