science term 2 year 10

• Conductors vs. InsulatorsConductors, like copper, allow electrons to move freely between atoms, enabling electricity to flow. Insulators, such as plastic, prevent electron movement, stopping electrical flow. This difference makes copper ideal for wires and plastic ideal for insulating wire exteriors.
• Materials for Electrical Wiring

  Electrical wires have a conductive core, usually made of copper, and an insulating exterior made of plastic or rubber. Copper's conductivity allows easy electron flow, while the insulating layer prevents unwanted electrical contact.
• Measuring Current and Voltage

  Current is measured with an ammeter and is expressed in amps (A). Voltage is measured with a voltmeter and is expressed in volts (V). Current is the rate of electron flow, while voltage is the energy per charge.
• Resistance

  Resistance measures how difficult it is for electrons to move through a material and is measured in ohms (Ω). In series circuits, resistance increases with each additional component, lowering the current. In parallel circuits, resistance decreases, increasing the current.
• Ohm’s Law

  Ohm’s Law relates voltage (V), current (I), and resistance (R) using the formula V = I × R. From this, you can derive I = V ÷ R and R = V ÷ I.
• Series vs. Parallel Circuits

  In series circuits, adding more bulbs increases resistance and decreases current, making bulbs dimmer. In parallel circuits, each bulb gets the full voltage, making them brighter. Parallel circuits are also more reliable since one broken bulb doesn’t affect others.
• Calculations with Ohm’s Law and Power

  Using Ohm’s Law, you can calculate various electrical properties:

  • Current (I) = Voltage (V) ÷ Resistance (R)
  • Power (P) = Voltage (V) × Current (I)
• Example Calculations

  For a circuit with a 24V battery and a 3Ω bulb:

  • Current (I) = 24V ÷ 3Ω = 8A
  • Power (P) = 24V × 8A = 192W

  For a 50W bulb with a 2A current:

  • Voltage (V) = 50W ÷ 2A = 25V
  • Resistance (R) = 25V ÷ 2A = 12.5Ω
• Correct Connection of Meters

  Ammeters should be connected in series to measure current correctly. Voltmeters should be connected in parallel to measure voltage accurately.
• Static Electricity

  Rubbing a balloon against hair transfers electrons to the balloon, giving it a negative charge and leaving the hair positively charged. The opposite charges attract, causing the hair to stick to the balloon
• Van de Graaff Generator

  Touching a Van de Graaff generator transfers electrons from you to the generator, positively charging your hair. Each strand repels the others due to the same charge, causing hair to stand on end.
• Solar Power and Charging

  A solar panel producing 9V with a phone resistance of 10Ω will have a current of 0.9A (I = 9V ÷ 10Ω). The power, or energy per second, will be 0.81W (P = 0.9A × 9V). As the phone charges, its resistance increases, reducing the current and slowing the charging speed.
• Advantages and Disadvantages of Parallel Circuits

  Parallel circuits keep bulbs brighter and allow independent switching, making them more reliable than series circuits. However, they are more complex and costly to set up.
• Solar Power in New Zealand

  Solar power is renewable and doesn’t contribute to climate change, but it only works during the day. Batteries are needed to store energy for nighttime use, impacting reliability and cost.
• Graphing Voltage and Current

  To analyze circuits, you can create tables and graphs of voltage against current to visualize the relationship and calculate averages.
• Electric Charge

  Electricity is generated by the movement of electrons from one atom to another. In New Zealand, the primary source of electricity is hydroelectric power. The 'grid' refers to the network of power lines and transformers that distribute electricity from power plants to homes and businesses.
• Other Sources of Electricity in NZ

  Geothermal energy uses heat from the Earth's interior to produce steam that drives turbines, mainly in the Taupo and Rotorua regions. Wind power, which turns turbine blades to generate electricity, is prominent in Wellington, Manawatu, and Taranaki. Solar power, where solar panels convert sunlight directly into electricity, is distributed across the country, especially in residential areas.
• Static Electricity

  Static electricity occurs when positive and negative charges are unbalanced, causing electrons to move from one object to another, creating an imbalance. This interaction between charges, called electric force, causes like charges to repel and unlike charges to attract. Objects become charged through friction, conduction, or induction.
• Electric Current

  Electric current, defined as the flow of electric charge through a conductor, is measured in amperes (A). Examples of electrical energy sources include car batteries and household appliances. Conductors, such as metals, allow electricity to flow easily, whereas insulators like rubber and glass prevent its flow.
• Electric Circuits and Symbols

  Electric current flows due to a voltage difference, with electrons moving from negative to positive terminals. Circuit diagrams use symbols to represent components such as cells, batteries, wires, switches, bulbs, and resistors. Current in circuits is measured using an ammeter or multimeter. In a series circuit, the current is the same throughout, while in a parallel circuit, the current splits between branches.
• Voltage

  Voltage, defined as the potential difference between two points, is measured in volts (V) using a voltmeter or multimeter. In series circuits, voltage is divided among components, whereas in parallel circuits, voltage remains the same across each branch.
• Electrical Safety

  Safety measures include proper insulation, grounding, circuit breakers, and fuses to prevent overloading and short circuits
• Resistance


  Opposes the flow of current, measured in ohms (Ω), calculated using R=V/I
• Power


  Rate of energy transfer, measured in watts (W), calculated using P=VI
• Magnetism


  • Like poles repel, unlike poles attract, field lines flow from north to south
• Magnetic force field


  Drawn around a magnet to show the direction and strength of the magnetic force
• Solar power advantages


  • Renewable, environmentally friendly
• Solar power disadvantages


  • Weather dependency, high initial costs
• Fair testing


  1. Controlling variables

  2. Plotting graphs with titles and units

  3. Calculating averages
• Motion types


  Constant speed, acceleration
• Motion quantities and symbols


  Distance (m), time (s), speed (m/s), v=d/t
• Distance/time graph


  Slope represents speed, steeper slope indicates faster speed
• Forces


  Pushes, pulls, twists, or squeezes, measured in newtons (N)
• Force measurement


  Using a force meter
• Balanced forces


  Keep an object at rest or moving at constant speed
• Unbalanced forces


  Cause acceleration in the direction of the net force
• Weight


  Force of gravity, calculated as W=mg
• Mass


  Amount of matter
• Friction types


  • Static
  • Kinetic (sliding)
  • Rolling
  • Fluid
• Factors affecting friction


  • Surface roughness
  • Normal force
  • Material properties
  • Temperature