SNC1W: Electricity Unit Test Review Package

Key Concepts

• Energy

  • Definition of Energy

    • The ability to do work. 

  • Forms of Energy

    • CHEMICAL POTENTIAL ENERGY

      • This is energy that is released when chemical reactions take place.

      • Sources of chemical energy include: fuel, food and batteries.

    • ELASTIC POTENTIAL ENERGY

      • This is the energy stored in a stretched or compressed object  that wants to return to its original state

    • ELECTRICAL ENERGY

      • This is the energy transferred by an electric current.

    • SOUND ENERGY

      • This is energy in the form of a sound wave.

    • THERMAL ENERGY

      • This is the energy of an object due to its temperature.  Also known as heat energy

    • LIGHT ENERGY

      • This is energy in the form of visible electromagnetic radiation.

    • NUCLEAR ENERGY

      • This is energy that is released when nuclear reactions take place.  This is the source of the Sun’s energy.

  • Energy Transformations

  • Useful vs. Wasted Energy

    • When an energy transformation takes place, the energy given to the device (input energy) is transformed into useful and wasted energy

    • Useful energy: Energy transferred to the intended purpose of the device

    • Wasted energy: Energy transferred to an unintended purpose.  

• Atomic Structure and Role in Electricity

  • Parts of an Atom

    • Subatomic particles: Protons, Electrons, and Neutrons

    • Nucleus of an atom: has protons and neutrons

    • Orbital of an atom: where electrons are kept

    • Protons and neutrons impact the mass of an atom (mass is the sum of two numbers)

• Metallic Bonding 

  • In a metallic bond, metal atoms share a “sea of electrons” that are free to move around the entire structure, resulting in 3 key properties: 

    • Conductivity: The free electrons in metals allow them to conduct electricity and heat effectively. When a voltage is applied, these electrons move freely, carrying electrical current. Similarly, their motion helps transfer thermal energy throughout the metal.

    • Malleability and Ductility: Metals can be hammered into sheets (malleability) or drawn into wires (ductility) without breaking. This is because the "sea of electrons" allows the metal atoms to slide past each other without breaking the bond, unlike in ionic or covalent structures.

    • High Melting and Boiling Points: The attraction in metallic bonds is strong, which generally leads to high melting and boiling points. More energy is needed to break the bonds between atoms.
      
      

• Static Electricity

  • Definition

    • Stationary electrical charges that sit on the surface of objects. When objects of different materials are rubbed together one will gain electrons while the other will lose electrons. 

    • The electrostatic series: Arranges materials based on their ability to hold on to electrons. The material that is higher on the series will hold a more positive charge(they have a weaker hold on electrons). 

    • Electric forces: Either attractive or repulsive produced by objects carrying an electric charge. “a property of the space around a charged object where the effect of its charge can be felt by other objects”

      • Dependent on: 

1. The net charge on on each object. Larger net charge = stronger electric force

2. The distance between the two objects: greater distance = weaker field = weaker force

• Methods of charging

  • CHARGING BY FRICTION: Charging by friction, charge depends on the electrostatic series. 

  • CHARGING BY CONDUCTION: Occurs when a charged conductor makes contact with a neutral conductor. The neutral object will get the same charge as the object that charges it. This occurs with conductors because they allow charges to move through their material easily. 

  • CHARGING BY INDUCTION: A charged object brought near a neutal object, causing a temporary movement of electrons. 

• Laws of Electric Charge

  • Opposite charges attract

  • Like charges repel

  • Negative/Positive charges and neutral attract
    
    
    

• Electrical Circuits and Components

  • Current

    • The flow of electrons through a conductor measured in Amps. 

    • Requirements: Power supply- provides energy to move electrons, Conductors ~ a path for electrons to flow, Load ~ A device that uses electrical energy. 

  • Potential Difference

    • There are too many electrons to count them one by one. For this reason we count them in packages called coulombs. 

    • Electrons carry potential electrical energy. Electrical loads use said energy to do work. Electrical sources replenish electrical potential energy. The amount of electrical potential energy per Coulomb is called a volt. 

    • Since this is measured by determining the difference in electrical potential energy between 2 points in a circuit, voltage is called potential difference. 
      
      

• Batteries and Potential Difference

  • How Batteries Work: energy transformations

    • When a battery is connected to a circuit, it provides enough energy to push electrons in a uniform manner (when one starts moving they all move, law of attraction →they repel). 

    • Before use of a battery they don’t move uniformly, after the use of a battery they move in one direction. 

• Experimentally Determined Relationships

  • Potential Difference in Series Circuits

    • In a series circuit, the voltage from the battery is split between all of the loads. The bulbs are dim (or only one lights up) because they share the same electrical potential energy. 

  • Potential Difference in Parallel Circuits

    • In a parallel circuit, the voltage stays the same/similar across the circuit because each coulomb needs to pass through only 1 bulb since there are multiple paths. 

  • Current in Series Circuits 

    • The current stays the same because there’s only one pathway for all the electrons. 

    • Current is impacted by resistance. As more loads/wires are added the resistance increases and the current decreases. 

  • Current in Parallel Circuits

    • The current is divided by the # of arms in the circuit and is shared by all of the bulbs since there are multiple pathways. 

    • Current is impacted by resistance. The resistance decreases as more components are added because there are more paths for electrons to flow through leading to an increase in current.