Science Exam

• Kinetic Energy


  Found in moving objects like cars, bicycles and running water
• Potential Energy 


  Stored Energy - Includes Gravitational PE (in raised objects), Elastic PE (in stretched or compressed objects like springs)
• Thermal Energy


  The internal energy of an object is due to the random motion of its molecules. It in icreases due to temperature. (Such as heated water)
• Chemical Energy


  Stored in chemical bonds and released in chemical reactions. (Found in food, batteries, fuel)
• Electrical Energy


  The energy from electric currents is used to power devices like lamps and computers.
• Nuclear Energy


  The energy released from Energy released from nuclear reactions (eg. in nuclear powerplants)
• Light Energy (Radiant Energy)


  Energy from electromagnetic waves, such as sunlight or light from a bulb.
• Sound Energy


  Energy carried by sound waves, like music from speakers.
• Definition of Energy

  The capacity of an object or system to do work or cause physical change, measured in Joules (J)
• Calculation of Kinetic Energy

  KE=1/2​mv2, where m is mass and v is speed
• Calculation of Gravitational PE

  GPE = mgh, where g is the acceleration due to gravity
• Kinetic Energy and speed

  Kinetic energy increases with the square of speed; if the speed doubles, kinetic energy increases four times.
• Kinetic Energy and Mass

  Kinetic energy is directly proportional to the object's mass. If an object's mass doubles (keep the speed constant), the kinetic energy doubles.
• Elastic PE and Shape

  Elastic PE is the energy stored in objects that can be stretched (like rubber bands) or compressed (like springs). The amount of energy stored depends on how much the object is deformed.
• Gravitational PE and Mass/Height

  GPE depends on both objects' mass and height and gravitational field strength: GPE = mgh. The higher the object or the heavier it is, the more GPE it has
• Energy Transfer vs. Energy Transformation


  • Energy Transfer: The movement of energy from one place or object to another without changing form (eg. heat moving from a stove to a pot).
  • Energy Transformation: Energy changing from one form to another. (eg. A toaster converts electrical energy into thermal energy).
• Energy Flow Diagrams


  Represents energy transfers and transformations with arrows showing the flow. eg.

  sun -> solar panel -> Battery
• Useful and Waste Energy

  • Useful Energy: The energy output that achieves the intended purpose (eg. light from a lamp).
  • Waste Energy: Energy that does not contribute to the intended purpose (eg. heat from a lamp).
• Calculating Energy


  Measures how effectively energy is used. (Higher percentage indicated better efficiency)

  Efficiency=(Total Energy Input

  Useful Energy Output​)x100%
• Electrical Current, Voltage, and Resistance

  • Current (I): Flow of electric charge measured in amperes (A).
  • Voltage (V): Electric potential difference that drives the current, measured in volts (V).
  • Resistance (R): The opposition to current, measured in ohms (Ω)
• Circuit Diagrams With Symbols

  A = Ammeter

  V = Volmeter

  
• Ohm's Law


  Ohm's law relates current, voltage, and resistance

  • V = I x R
  • I = V/R
  • R = V/I
• Magnetism Definition

  Magnetism is the force exerted by magnets by magnets that attract or repel each other. It arises from the movement of electric charges.
• Magnetic Poles Interaction

  • Opposite poles attract (north & south)
  • Like poles repel (north & north, south & south)
• Magnetic Fields


  Magnetic fields are visualised as the lines that surround a magnet, flowing from North to South (the closer the lines, the stronger the field).
• Magnetic Fields from Electric Currents


  Electric currents create magnetic fields around them. This is the principle behind electromagnets

  • Right-hand rule: If the thumb points in the current direction, curled fingers show the field's direction.
• Electromagnets in Electronic Devices


  An electro magnetic is created when electric current flows through a coil of wire, producing a magnetic field. Used in doorbells etc where controllable magnetism is needed.
• Electricity Generation with Magnets


  Devices like generators produce electricity by rotating magnets near coils of wire or rotating coils in a magnetic field. This motion creates current in the wire, converting mechanical energy into electrical energy.
• Currents Produced by Magnetic Fields


  When a conductor moves through a magnetic field, or when a magnetic field changes around a conductor, it creates an electric current—a process called electromagnetic induction used in generators to produce electricity.
• How to convert Joules (J) to Kilojoules (kJ)

  Divide by 1,000, since 1 kilojoule is equal to 1,000 joules

  Eg., if you have 5,000 joules, you would have 5 Kilojoules

  5,000/1,000 = 5