Physics Chapter on Electrical Resistance and Ammeters

Grade 9 Science Final Exam Overview

•  The exam is worth 10% of the final mark.
•  Allowed materials include pens, pencils, erasers, and a calculator. A periodic table with formulas is provided, last page of the exam.
•  The exam covers 75 marks over 90 minutes.
•  Breakdown of sections and time allocation:
  • Knowledge (30 multiple choice questions): 28 marks, 30 minutes
  • Thinking (short answer): 23 marks, 25 minutes
  • Communication (short answer): 10 marks, 10 minutes
  • Application (connections): 14 marks, 15 minutes
  • Review: 10 minutes

5.1 Particle Theory of Matter

•  Matter is made up of tiny particles (atoms or molecules), which are in constant motion.
•  The properties of matter (e.g., state or behavior) depend on how these particles interact.
•  Key points:
  • All matter is made of particles too small to see.
  • Particles are constantly moving (vibrating, sliding past each other, freely).
  • There are spaces between particles in different states (solids, liquids, and gases).
  • Particles attract each other; the strength varies depending on the state. - Temperature affects particle motion; heat makes particles move faster, and cooler temperatures slow them down.
•  States of Matter:
  • Solids: Particles tightly packed, fixed shape and volume.
  • Liquids: Particles closer but can move past each other; fixed volume, changing shape.
  • Gases: Particles far apart, move freely; no fixed shape or volume.
•  Changes of State:
  • Melting (solid to liquid)
  • Freezing (liquid to solid)
  • Evaporation (liquid to gas)
  • Boiling (liquid to gas)
  • Condensation (gas to liquid)
  • Sublimation (solid to gas)

5.2 Physical Properties

•  Physical properties describe matter without changing the substance.
•  Examples of physical properties:
  • Color
  • Density
  • Melting point
  • Boiling point
  • State of matter
  • Solubility
  • Hardness
  • Conductivity
  • Magnetism
  • Viscosity
  • Transparency
•  Importance of physical properties: Physical properties are used for identifying substances

5.3 Chemical Properties

•  Chemical properties describe how a substance reacts with other substances.
•  These properties are only observed during a chemical reaction.
•  Examples of chemical properties:
  • Reactivity with water
  • Reactivity with oxygen
  • Flammability
  • Acidity or basicity
  • Toxicity
  • Corrosion resistance

Qualitative vs. Quantitative Properties

•  Qualitative properties describe qualities or characteristics without numbers (e.g., color, texture).
•  Quantitative properties describe measurable properties with numbers and units (e.g., mass, temperature).
•  Key Differences: Qualitative properties are descriptive while quantitative measurements are numerical.

5.6 Characteristic Physical Properties (Density Calculations)

•  Density measures how tightly matter is packed together.
• Formula: density = mass / volume
•  Units: grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

GRASP Method

•  G: Given information (list the known values).
•  R: Required information (list what the problem is asking).
•  A: Apply the formula(s) that relate known to unknown.
  • Solve for the unknown, using the given information.
• S: Solve using the formulas and steps.
• P: Provide the final answer and check if the answer is reasonable.

Unique Properties of Water

•  High Specific Heat: Water absorbs a lot of heat energy before changing temperature, helping stabilize environments. 
•  High Heat of Vaporization: Water absorbs significant heat before evaporating, helping regulate body temperature.
•  Density Anomaly: Ice floats because it's less dense than liquid water; this property is crucial for aquatic life in cold climates.
•  Cohesion and Adhesion: Water molecules stick together (cohesion) and to other substances (adhesion), resulting in water droplet formation, surface tension, etc.

6.1 Elements, Counting Atoms, Metals vs. Non-metals

•  Elements are pure substances made of a single type of atom.
•  Elements are organized on the Periodic Table by atomic number.
•  Atoms are the smallest unit of an element
•  Atomic number: Number of protons in an atom
•  Atomic mass: Sum of protons and neutrons in an atom
•  Molecule: A group of two or more atoms bonded together.
• Metals are typically found on the left-hand side of the Periodic Table, while non-metals are found on the right-hand side. Metalloids have properties of both metals and non-metals.

### 6.4 Patterns in the Periodic Table

•  Elements are arranged in the modern periodic table by increasing atomic number.
•  Elements in the same group (vertical column) have similar chemical properties due to their similar number of valence electrons. 
•  Elements in the same period (horizontal row) experience a trend in atomic radius, ionization energy, and electronegativity.
•  Key trends: Reactivity
  • Alkali Metals are highly reactive; reactivity increases down the group.
  • Halogens are highly reactive non-metals; reactivity decreases down the group.
  • Noble gases are non-reactive (inert) because they have full outer shells.

6.6 Theories of the Atom

-Early atomic models (Dalton, Rutherford, Bohr) explained the structure of the atom and energy levels of electrons.

•  Protons carry a positive charge and are located in the nucleus of the atom. 
•  Neutrons are neutral and located in the nucleus.
•  Electrons carry a negative charge and are found surrounding the nucleus.
• Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses. 

6.7 Bohr Diagrams

• Bohr diagrams show the arrangement of electrons in energy levels (or shells) surrounding the atom's nucleus.

12.3 Electrical Energy, Symbol, Unit

• Electrical energy is the energy stored in electric charges.
•  Symbol: E or W (Work)
•  Unit: the Joule (J)
•  Connection to current and resistance -Electrical energy can be derived from various sources (e.g., nuclear, hydroelectric, wind, fossil fuels, solar).

12.4 AC/DC Definitions

• Alternating Current (AC): Current repeatedly changes direction.
• Direct Current (DC): Current flows in a constant direction. -AC is more suitable for long-distance transmission than DC because of transformer efficiency. -DC is commonly used in electronic devices.

12.5 Generating Electrical Energy

•  Different sources of electrical energy, their mechanisms, and advantages/disadvantages are explored.
•  Nuclear power
•  Hydroelectric power
•  Solar power
•  Wind power
•  Fossil fuels

13.1 Series and Parallel Circuits

• Series circuits have components connected end-to-end; current flows through each component sequentially.
• Parallel circuits have components connected across each other; current flows along multiple pathways or branches.
• Circuit diagrams of series and parallel circuits should use appropriate symbols for components (resistors, lamps) as well as ammeters and voltmeters.

13.3 Current, How to Connect Ammeters

• Symbol for current is I
• Current is measured in amperes (A).
• Ammeters are connected in series with the component to measure current flowing through that component.

13.5 Voltage, How to Connect Voltmeters

• Symbol for voltage is V
• Voltage is measured in volts (V).
• Voltmeters are connected in parallel to measure voltage across components.

13.7 Electrical Resistance

• Resistance is a measure of how a material hinders the flow of electric current.
• Resistance is measured in ohms (Ω). -Factors influencing resistance include:
• Material of the conductor
• Length of the conductor
• Cross-sectional area of the conductor
• Temperature of the conductor

13.9 Ohm's Law Calculations

• Ohm's Law relates voltage (V), current (I), and resistance (R).
• Formulae: V=I*R, I=V/R, R=V/I
• Units: V (volts), I (amperes), R (ohms).

2.1 The Spheres of the Earth

• Lithosphere: Earth's solid outer layer (crust and upper mantle)
• Hydrosphere: All water on Earth (oceans, rivers, lakes, glaciers)
• Atmosphere: Gases surrounding the Earth
• Biosphere: All living organisms on Earth and their interactions.
• Anthrosphere: Human influence on the environment.

2.2 Ecosystems

• Ecosystem: A community of living (biotic) and non-living (abiotic) organisms interacting in an area.
• Trophic levels: Producers (create food), primary consumers (eat producers), secondary consumers (eat primary consumers) etc.
• Food webs: Interconnected food chains representing energy flow and relationships. -Sustainable ecosystems: maintain health without depletion of resources.
• Unsustainable ecosystems: cannot maintain the biodiversity over a long time due to excessive exploitation or other changes.

2.4 Energy Flow in Ecosystems

• Photosynthesis: Use sunlight, water, and CO2 to make glucose (energy).
• Cellular respiration: Glucose+O2>CO2+H2O (release chemical energy as a usable form of ATP for cell's use).

2.5 Food Webs

• Trophic levels: Producers (plants), primary consumers (animals that eat plants), secondary consumers (animals that eat primary consumers) and decomposers.
• Energy flow: 10% Rule (only 10% usable energy from one level passes to the next higher trophic level.)

2.6 Cycling of matter in ecosystems & 2.7 Biotic and Abiotic influences on Ecosystems

• Cycling of matter: The continuous movement of elements like carbon, nitrogen, and water through an ecosystem's living and non-living components.
• Limiting factors: Biotic factors (like competition, predation, and symbiosis) and abiotic factors (like water, sunlight, temperature).
• Carrying capacity: The maximum population size of a species an environment can sustain over time.

3.3 Biodiversity

•  Biodiversity is the variety of life in an ecosystem.
•  Different species of plants, animals, fungi, and microbial organisms are included.
• Definitions:
  • extinct
  • Extirpated
  • Endangered
  • Threatened

6.4 Patterns in the Periodic Table

• Elements are organized into groups and rows (similar chemical behavior across periods, increasing atomic number).

• Key trends in periodic table: Reactivity (alkali metals, halogens), atomic size, ionization energy, electronegativity.

• These are just some examples, and the exam may have further details.

Test your understanding of Ohm's Law and the concepts of electrical resistance in this quiz. You'll explore essential topics such as the function of ammeters, the difference between conductors and insulators, and the characteristics of series circuits. Perfect for students studying physics and electricity!