Lecturer Physics Past Paper 03-06-2023 by SPSC

Q21: A positive change moving with a constant velocity v enters a region of a uniform magnetic field pointing out the page. What is the direction of the magnetic force on the charge?

مستقل رفتار کے ساتھ چلنے والی ایک مثبت تبدیلی صفحہ کی نشاندہی کرنے والے یکساں مقناطیسی فیلڈ کے ایک خطے میں داخل ہوتی ہے۔ چارج پر مقناطیسی قوت کی سمت کیا ہے؟

To the top of the page

To the bottom of the page

Right

None of these

Explanation

The magnetic force on a moving charge is given by Lorentz force: $F = q (v \times B)$

Using the right-hand rule, point your fingers in the direction of velocity (v), curl them toward the magnetic field (out of the page), and your thumb points in the direction of force.

For a positive charge, the force is toward the top of the page.

Q22: The Antonym of Ingenious is?

Devious

Talented

Clever

None of these

Q23: The atomic diameter of a BCC crystal (if a is lattice parameter) is _____?

a/(4/√3)

a/4/13)

al(4/12)

None of these

Explanation

In a Body-Centered Cubic (BCC) lattice, the relation between the lattice parameter a and atomic radius r is: $4 r = \sqrt{3} a$

Since atomic diameter = 2r, solving gives: $Atomic Diameter = \frac{4 r}{2} = \frac{a}{4 / \sqrt{3}}$

Q24: If the distance between the charges doubles, the coulomb's force between the charges _____?

اگر چارجز کے درمیان فاصلہ دوگنا ہوجاتا ہے تو ، چارجز کے درمیان کولمب کی طاقت _____؟

One-fourth

Halves

Distance between the charges

None of these

Explanation

According to Coulomb’s Law, the electrostatic force $F$ is inversely proportional to the square of the distance between the charges:
$F propto frac{1}{r^2}$

If the distance doubles ( $r to 2r$ ), the force reduces to one-fourth of its original value:
$F' = frac{F}{4}$

Q25: For an electronic state s = 1, and 1 = 1, the number of possible values of total angular momentum of an electronic are _____?

2

3

4

None of these

Q26: The equation E = mc^2 indicates that energy _____?

Is fundamentally different than mass

And mass are closely related

Equals mass moving at the speed of the light square

None of these

Explanation

Einstein’s equation $E = mc^2$ shows that energy and mass are interchangeable, meaning mass can be converted into energy and vice versa.

This principle is fundamental in nuclear reactions, where small amounts of mass release large amounts of energy.

Q27: Relativistic Mechanics produces results different from classical mechanics for bodily?

متعلقہ میکانکس جسمانی طور پر کلاسیکی میکانکس سے مختلف نتائج پیدا کرتا ہے؟

Zero velocity

Low velocities

Very high velocities

None of these

Explanation

Relativistic mechanics differs from classical mechanics when objects move at speeds close to the speed of light ( $v approx c$ ).

At low velocities, classical mechanics gives accurate results, but at very high velocities, effects like time dilation and mass increase become significant.

Q28: During one oscillation, phase of oscillation changes by _____?

ایک دوہری کے دوران ، _____ کے ذریعہ دوئم کے مرحلے میں تبدیلی آتی ہے؟

π⁄2 rad

π rad

2π rad

None of these

Explanation

In one complete oscillation (one full cycle), the phase of an oscillating system changes by $2pi$ radians.

This corresponds to the system returning to its starting position in a periodic motion, such as simple harmonic motion.

Q29: Canonical transformations can often be conveniently found or verified by using a ______?

کا استعمال کرکے کیننیکل تبدیلیاں اکثر آسانی سے پائی جاسکتی ہیں یا اس کی تصدیق کی جاسکتی ہیں؟ _____

Separation tensor

Degenerating function

Generating function

None of these

Q30: Divergence of a vector at a point in a vector field is _____ quantity.

ویکٹر فیلڈ میں ایک نقطہ پر ویکٹر کا انحراف _____ مقدار ہے۔

A scalar

A vector

Both A and B

None of these