Notes, summaries, assignments, exams, and problems for Physics

Biology Fundamentals

Genetics: DNA and RNA

• DNA: Double helix structure; carries genetic information. Bases pair A–T and C–G.
• RNA: Single strand; uses Uracil (U) instead of Thymine (T); assists in protein synthesis.

Cell Division

• Mitosis: Results in two identical daughter cells; essential for growth and repair.
• Meiosis: Results in four genetically different cells; produces gametes (sperm and egg).

Chromosomes

• Humans possess 23 pairs, totaling 46 chromosomes:
  • 22 pairs are autosomes.
  • 1 pair consists of sex chromosomes (X/Y).
• Sex determination: Males are XY; Females are XX.

Inheritance Principles

• Dominant Allele: Expressed even if only one copy is present.
• Recessive Allele: Expressed only when two copies are present.
• Use Punnett squares to predict trait outcomes

Fundamental Electrical Units

• Current: Ampere (A)
• Voltage: Volt (V)
• Resistance: Ohm (Ω)
• Power: Watt (W)
• Charge: Coulomb (C)

Metric Prefixes

• peta (P): 10^15
• tera (T): 10^12
• giga (G): 10^9
• mega (M): 10^6
• kilo (k): 10^3
• milli (m): 10^-3
• micro (µ): 10^-6
• nano (n): 10^-9
• pico (p): 10^-12
• femto (f): 10^-15

Significant Figures and Math

• Non-zero: Significant
• Leading zeros: Not significant
• Middle zeros: Significant
• Trailing decimals: Significant
• Addition/Subtraction: Match decimal places
• Multiplication/Division: Match significant figures

Core Electrical Concepts

When electrons move, they create current. Current is defined as I = Q/t, and voltage is V = W/Q.

Q represents coulombs (electrical charge). One volt is the potential difference between two points when one joule of energy... Continue reading "Electrical Engineering Fundamentals: Circuits and Components" »

Thermodynamics

First Law of Thermodynamics (Law of Energy Conservation)

Energy cannot be created or destroyed; it can only change forms.

Formula: ΔU=Q−W

Where: ΔU is the change in internal energy of the system, Q is the heat added to the system, W is the work done by the system.

Explanation: The total energy in a closed system remains constant. Energy can be transformed from one form to another (e.g., heat energy to mechanical energy).

Second Law of Thermodynamics

Key Concept: The total entropy (disorder) of an isolated system always increases or remains constant.

Formulas:

Entropy Change for Reversible Process: ΔS=Qrev /T

Where: ΔS is the change in entropy. Qrev is the heat added in a reversible process. T is the absolute temperature. Qirr is... Continue reading "Thermodynamics and Simple Harmonic Motion" »

SRML Half-Yearly Examination - 2080

Class: 9 | Subject: Science and Technology | Full Marks: 50 | Time: 2 Hours

Answer all questions.

Group - A: Multiple Choice Questions (8x1 = 8)

• a. What is the multiplier of the prefix 'micro'? (a) 10⁻⁶ (b) 10⁻⁹ (c) 10⁶ (d) 10⁻³
• b. What is the stalk of a mushroom called? (a) Pileus (b) Gills (c) Stipe (d) Hyphae
• c. Who was the proponent of the theory of natural selection? (a) Hugo de Vries (b) Charles Darwin (c) Lamarck (d) Gregor Johann Mendel
• d. If a load of 400 N is moved using an effort of 50 N, what is the Mechanical Advantage (MA)? (a) 8 (b) 50 (c) 400 (d) 100
• e. Which is not a source of non-renewable energy? (a) Coal (b) Biogas (c) Kerosene (d) Petrol
• f. Which is an example of a longitudinal wave?

Material Properties and Heat Treatment

• 2.1: Toughness
• 2.2: 14 × 10⁴, 90 × 10⁴
• 2.3: Stiffness
• 2.4: Toughness
• 2.5: Hardness
• 2.6: Malleability
• 2.7: 3–4% Carbon
• 2.8: Grey cast iron with ultimate tensile strength 300 N/mm²
• 2.9: Plain carbon steel (0.35–0.45% C, 0.7–0.9% Mn)
• 2.10: Mild steel
• 2.11: Less than 0.3% carbon
• 2.12: Sulphur
• 2.13: Chromium
• 2.14: Chromium
• 2.15: Above upper critical temperatures, cooled in still air
• 2.16: Case-hardening
• 2.17: Cyaniding
• 2.18: Case-carburising

Manufacturing and Tolerances

• 3.1: Aluminium
• 3.2: Fibre lines arranged in a predetermined way
• 3.3: Very small fillet radius
• 3.4: Easy removal of forged part from die cavities
• 3.5: Tolerances given on both positive and negative sides
• 3.6: Tolerance zone of hole and shaft overlap
• 3.7:

Electrostatics and Resistance Solved Problems

Point of Zero Electric Field Intensity

Vicinity Equal to Zero:
Q₁ = -20 × 10^-6 C, Q₂ = +5 × 10^-6 C, r = 2 m
r₁ = (2 + x) m, r₂ = x m

The electric field intensity at P due to Q₁:

E₁ = (1 / 4πε₀) × (Q₁ / r₁²)
= (9 × 10⁹ × 20 × 10^-6) / (2 + x)²

The electric field intensity at P due to Q₂:

E₂ = (1 / 4πε₀) × (Q₂ / r₂²)
= (9 × 10⁹ × 5 × 10^-6) / x²

At P, E = 0, therefore E₁ = E₂:

(9 × 10⁹ × 20 × 10^-6) / (2 + x)² = (9 × 10⁹ × 5 × 10^-6) / x²

4 / (2 + x)² = 1 / x²

(2 / (2 + x))² = (1 / x)²

2x = 2 + x

x = 2 m

Electric Properties of a Uranium Nucleus

Uranium:
e = 1.6 × 10^-19 C, r = 10^-10 m

Q = 9.2e
= 9.2 × (1.6 × 10^-19 C)
= 14.72 × 10^-19 C

(i) Electric Field (E):
E = (1 / 4πε₀) × (Q / r²)
= (9 ×... Continue reading "Physics Solved Problems: Electrostatics and Resistance" »

Chapter 27: Bridge Engineering Through History

Truss beams are strengthened by a stiff framework above or beneath the arch, supported by arch suspension, hanging cables, or pontoons made of boats or devices. Cantilever beams are supported only on one end.

Roman and Medieval Bridges

The largest Roman bridges were aqueducts. The best-known example is the Pont du Gard in France. During the Middle Ages, bridges were placed under the care of a religious order. These bridges were strongly fortified with huge towers. The most famous bridge of this period was the London Bridge, located over the Thames River. It eventually fell into disrepair and required reconstruction.

Renaissance and Modern Bridges

Three notable bridges built during the Renaissance include:... Continue reading "Evolution of Bridge Engineering and Skyscraper Architecture" »

Bernoulli's Equation and Energy Balance

Since the fluid is incompressible, A₁Δx₁ = A₂Δx₂ = ΔV.

Work–Energy Principle Derivation

The work done on the fluid is due to the pressure acting on it.

Therefore, the work done, ΔW = F₁Δx₁ - F₂Δx₂

= P₁A₁Δx₁ - P₂A₂Δx₂

= P₁ΔV - P₂ΔV

ΔW = (P₁ - P₂) ΔV

Change in kinetic energy, ΔKE = KE₂ - KE₁

= &frac12 mv₂² - &frac12 mv₁²

ΔKE = &frac12 m (v₂² - v₁²)

= &frac12 ρ ΔV (v₂² - v₁²)

Change in potential energy, ΔPE = PE₂ - PE₁

= m g h₂ - m g h₁ = m g (h₂ - h₁)

Since m = ρ ΔV, ΔPE = ρ ΔV g (h₂ - h₁)

Using the work–energy principle,

ΔW = ΔKE + ΔPE

(P₁ - P₂) ΔV = &frac12 ρ ΔV (v₂² - v₁²) + ρ ΔV g (h₂ - h₁)

Therefore, P₁ - P₂ = &frac12 ρ (v₂² - v₁²) + ρ g (h₂ - h₁)

Rearranging

Young's Double Slit Experiment (YDSE)

Concept: In 1801, Thomas Young performed an experiment where he passed light through two narrow slits and observed an interference pattern on a screen. This pattern consists of alternating bright and dark fringes.

Experimental Setup

• Monochromatic Light: Light of a single wavelength falls on a primary slit S.
• Slit Arrangement: From slit S, light travels to two secondary slits, S₁ and S₂.
• Diffraction and Interference: Light diffracts from S₁ and S₂ and interferes on the screen.
• Constructive Interference: This occurs where waves meet in phase, resulting in a bright fringe.
• Destructive Interference: This occurs where waves meet out of phase, resulting in a dark fringe.

Fringe Width Derivation (W)

Let:

• D = Distance between

Common Circuit Symbols and Components

• Switch: Used to open or close the circuit.
• Light Bulb: Designed to shine when current passes through it.
• Voltage Source (Battery): Produces electric current using chemical or physical properties of different materials.
• Conductor (Wire): Provides a path through which electric charge can flow.

Series vs. Parallel Circuits

• Series: Requires minimal wire; all elements must be working for the circuit to function.
• Parallel: Features several branches; provides more available power.
• Similarity: Both configurations require a battery or voltage source.

Electromagnets and Electric Motors

Uses of an Electromagnet

Electromagnets are used to pick up objects, write data, and power motors.

Increasing Electromagnet Strength

To increase... Continue reading "Essential Physics Principles and Electrical Circuits" »