EVERYDAY SCIENCE
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
مندرجہ ذیل میں سے کون سا بیان غلط ہے؟
- Rough surfaces are better radiators than smooth surfaces
- Highly polished mirror surfaces are very good radiators
- Black surfaces are better absorbs that white ones
- Black surfaces are better radiators then white ones
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Explanation
- Rough and black surfaces are good radiators of heat.
- Smooth and polished surfaces are poor radiators and good reflectors.
- Black surfaces absorb and emit heat better than white surfaces.
- Highly polished mirror surfaces reflect heat instead of radiating it.
Last verified on 05-06-2026
- r₁² / r₂²
- (r₁ / r₂)²
- (r₂ / r₁)²
- None of these
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Explanation
- Rate of heat loss is proportional to surface area of the body.
- Surface area of a sphere = 4πr².
- So, heat loss ratio = r₁² : r₂².
Last verified on 05-06-2026
اوور ڈیمپنگ کا نتیجہ کیا ہوتا ہے؟
- Slower return to equilibrium
- Faster return to equilibrium
- Equilibrium is never achieved
- Unrhythmic to equilibrium
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Explanation
- Over-damping occurs when damping force is very large.
- The system returns to equilibrium without oscillating.
- Because of strong resistance, motion becomes very slow.
- It takes more time compared to critical damping.
Last verified on 05-06-2026
فزیکل پینڈولم کا دورانیہ کیا ہوتا ہے؟
- T = 2π√(I/Mgd)
- T = 2π√(1/x)
- √T = 4¹/MgR
- All of these
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Explanation
- Physical pendulum depends on moment of inertia (I) and distance (d) from pivot to center of mass.
- Time period increases when mass is farther from pivot (larger d).
- Standard formula is T = 2π√(I/Mgd).
Last verified on 05-06-2026
فیوجن ری ایکٹر میں نیوکلیائی ذرات کے درمیان الیکٹرو اسٹیٹک ریپلسن کو ختم کرنے کے لیے کیا ضروری ہوتا ہے؟
- Very high pressure
- Very high temperature
- Very small volume
- All of these
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Explanation
- In a fusion reactor, nuclei must overcome strong electrostatic (Coulomb) repulsion.
- To achieve fusion, extremely high energy conditions are required.
- Very high temperature gives nuclei enough kinetic energy to approach each other.
- Very high pressure and very small volume increase collision probability.
Last verified on 05-06-2026
زینر ڈائیوڈ کی بہترین وضاحت کیا ہے؟
- It operates in reverse region
- It is a constant voltage device
- It is a constant current device
- All of these
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Explanation
- Zener diode is mainly used as a constant voltage regulator.
- It operates in the reverse breakdown region.
- In this region, voltage remains almost constant even if current changes.
Last verified on 05-06-2026
جب دو چارجز کے درمیان ہوا میں فاصلہ ہو اور ان کے درمیان ڈائی الیکٹرک شیٹ رکھ دی جائے تو ان کے درمیان برقی قوت پر کیا اثر ہوگا؟
- Decrease
- Increase
- Remain unchanged
- Become zero
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Explanation
When a dielectric is placed between two charges, the electrostatic force decreases.Dielectric materials get polarized in an electric field.
This polarization reduces the effective electric field between charges.
Hence, the force between charges becomes weaker than in air.
Last verified on 05-06-2026
- 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