Lecture Notes: Science Topics Overview

Overview

• Instructor: Hanjun, Science Tutor
• Focus: Electrical Systems, Digestive System, Transport System, Human Reproductive System
• Reminder: Previous topics for terms 1 and 2 available on YouTube
• Incentives: Stay for a cartoon game to win curated notes

Electrical Systems

Key Components

1. Electric Current

   • Definition: Flow of electrons in one direction in a circuit
   • Analogy: Like water flow in a river
   • Models: Conventional current model (positive to negative) vs. electron flow model (negative to positive)
   • Measurement: Ammeter in series, measured in Amperes

2. Potential Difference (Voltage)

   • Definition: Energy needed to move a charge across two points
   • Measured with a voltmeter
   • Concept: Identify points A and B in a circuit to measure component voltage

3. Resistance

   • Definition: Opposition to current flow
   • Relationship: Inverse with current (high resistance = low current)
   • Measurement: Ohms
   • Types: Fixed resistor (adds constant resistance), Variable resistor (alters resistance)

Series vs Parallel Circuits

• Series Circuits

  • One path; current is the same throughout
  • If one bulb fails, all bulbs affected
  • Total resistance is the sum of individual resistances

• Parallel Circuits

  • Multiple paths; current divides
  • If one bulb fails, others remain lit
  • Total voltage is same across each branch
  • More branches reduce total resistance

Ohm’s Law

• Formula: V = IR
• Applications: Calculating current, resistance, or voltage

Wiring in a Plug

• Three Wires: Live (current and potential difference), Neutral (current, no potential difference), Earth (safety)
• Safety Precautions: avoid damaged wires, wet conditions, overloading
• Devices: Circuit breakers and fuses for safety

Digestive System

Main Nutrients

• Carbohydrates: Energy
• Proteins: Growth and repair
• Fats: Insulation and energy

Digestion Process

• Breakdown of large molecules into smaller, absorbable ones
• Enzymes: Specific to nutrients, e.g., amylase for carbohydrates

Organ Processes

• Mouth: Mechanical chewing, salivary amylase for carbohydrates
• Esophagus: Peristalsis (no digestion)
• Stomach: Gastric juice (proteins digestion)
• Small Intestine: Major site for all nutrient digestion and absorption
• Large Intestine: Water reabsorption

Bile

• Aids in fat digestion (not an enzyme)

Transport System

Diffusion and Osmosis

• Diffusion: Movement from high to low concentration
• Osmosis: Water movement through a semi-permeable membrane

Blood Components

• Red Blood Cells: Transport oxygen
• White Blood Cells: Immune response
• Platelets: Clotting
• Plasma: Transport nutrients and waste

Blood Vessels

• Arteries: Away from heart, high pressure, thick walls
• Veins: Towards heart, low pressure, thin walls
• Capillaries: Exchange of substances

Plant Transport System

• Xylem: Water and minerals (root to plant)
• Phloem: Sugars (from leaves)

Human Reproductive System

Male and Female Anatomy

• Female: Ovaries, fallopian tubes, uterus, cervix, vagina
• Male: Testes, sperm ducts, penis

Puberty Changes

• Boys: Sperm production, voice deepens, body hair
• Girls: Egg release, menstruation, breast development

Menstrual Cycle

• Phases: Menstruation, repair, fertile period, maintenance

Birth Control and STIs

• Methods: Condoms, intrauterine devices, contraceptive pills
• STIs: Gonorrhea, syphilis (bacterial), HIV (viral)

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This summary captures the key concepts and details from the lecture material. Use it to reinforce learning and review important information.