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۔
غیر مساوی قوتوں کی کم سے کم تعداد کیا ہوگی جس کی رقم صفر کے برابر ہوسکتی ہے؟
1
2
3
None of these
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Explanation
To achieve a zero resultant force, at least three unequal forces are required to form a closed triangle in vector addition. Two unequal forces cannot cancel each other unless they are equal in magnitude but opposite in direction.
فوٹو الیکٹرک سیل میں ، خارج ہونے والے الیکٹران کو خارج کرنے کی رفتار _______ پر منحصر ہے؟
Work function of the metal
Frequency of the incident light
Intensity of the incident light
None of these
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Explanation
The kinetic energy of ejected electrons depends on the frequency of the incident light, as per Einstein’s photoelectric equation : K E = h f − ϕ KE = hf - phi where h h is Planck’s constant, f f is frequency, and ϕ phi is the work function. Intensity affects the number of emitted electrons but not their velocity.
مقناطیسی میدان میں منتقل ہونے والے چارج پر کام کرنے والی طاقت کا انحصار _____ نہیں ہوگا؟
Intensity of the magnetic field
Its mass
Amount of charge
None of these
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Explanation
The magnetic force on a moving charge is given by F = qvB sinθ , where q is the charge, v is velocity, and B is the magnetic field intensity. Mass (m) does not appear in this equation , so the force is independent of the charge's mass.
0.25%
2%
1%
None of these
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Explanation
Power in an electric bulb is given by P = I²R .If the current I decreases by 0.5% , then power decreases by (0.5 × 2) = 1% because power depends on the square of current.
40 W
30 W
90 W
None of these
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Explanation
When four equal resistors are connected in series, the total resistance (R_total) is:
R_total = 4R
The power dissipated (P) is:
P = V² / R_total
Given P = 10 W, we can rewrite the equation as:
10 = V² / (4R)
Now, if one resistor is connected across the same battery, the power dissipated (P') will be:
P' = V² / R
Comparing the two equations, we can see that:
P' = 4P
= 4 × 10 W
= 40 W
جب کسی مادے کو گرم کیا گیا تو ، اس کی چالکتا میں اضافہ کیا گیا تھا ، تو اسے مندرجہ ذیل میں سے کیا ہونا چاہئے؟
Metals
Insulators
Semi-conductors
None of these
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Explanation
In semiconductors , increasing temperature excites more electrons from the valence band to the conduction band, increasing conductivity. In contrast, metals have decreasing conductivity with temperature due to increased electron scattering.
4K
K/2
2K
None of these
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Explanation
The spring constant K K is inversely proportional to the length of the spring. When a spring is cut into two equal parts , each half will have double the original spring constant, i.e., 2 K 2K .
اگر چارج شدہ متوازی پلیٹ کیپسیٹرز کی پلیٹیں ایک دوسرے سے دور ہوجاتی ہیں ______؟
Voltage decreases
Energy increases
Voltage increases
None of these
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Explanation
The capacitance of a parallel plate capacitor is given by C = ε₀A/d , where d is the distance between the plates. If d increases, C decreases. The voltage across a capacitor is V = Q/C . Since Q remains constant and C decreases, V increases.
4:1
2:1
1:2
None of these
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Explanation
The kinetic energy gained by a charged particle in an electric field is given by KE = qV , where q is charge and V is the potential difference. Since kinetic energy is also KE = ½ mV² , equating both expressions gives V = √(2qV/m) .For particle A ( q ) and particle B ( 4q ), their velocities will be VA = √(2qV/m) and VB = √(8qV/m) .Taking the ratio : VA/VB = √(2qV/m) / √(8qV/m) = 1/2 .
جب آواز ایک میڈیم سے دوسرے میڈیم میں داخل ہوتی ہے تو کیا تبدیل نہیں ہوتا؟
Wavelength
Frequency
Speed
None of these
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Explanation
When sound travels from one medium to another, speed and wavelength change due to the change in the medium's properties. Frequency remains constant because it is determined by the source of the sound, not the medium.
