SNC1D Grade 9 Academic Science – Electricity Notes

 Static Electricity

  • A stationary electric charge, typically produced by friction, that causes sparks or crackling or the attraction of dust or hair.
  • Discharge
    • Building up a charge
    • More electrons flow out of you

OR

  • Less electrons flow out of you
Method of Charging Initial Charge on Objects Contact Between Objects Final Charge Movement of Electrons
Friction Both objects are neutral Lots of contact (the more contact the greater the charge) Opposite charges (one becomes +ve and one becomes –ve) Move from object with the weak hold on electrons to objects with the stronger hold
Conduction/Contact One object is neutral

One object is charged

Brief touch (no rubbing) Both objects have the same charge Attempt to balance charge on originally charged object
Induction (Temporary) One object is neutral

One object is charged

Moving the objects close together (no contact!) Both objects have the initial charges they had. Repel/attract in neutral object, depending on the other object’s charge. One side of the neutral object becomes negatively charged, but the overall object is still neutral.
Induction (Permanent) One object is neutral

One object is charged

Moving the objects close together (no contact!) Opposite charges (one becomes +ve and one becomes -ve)  

 

  • Currents
    • a flow of electricity which results from the ordered directional movement of electrically charged particles.
  • Protons, Electrons, Neutrons
    • Electrons: Negative
    • Protons: Positive
    • Neutrons: Neutral
    • Neutrals attract Negative/Positives
    • Negative/Positive attract Neutrals
    • “Likes” repels
    • “Opposite” attracts
    • Same=/=Same
    • Different=Different
    • PROTONS DO NOT JUMP/MOVE!!!
    • Metals, saltwater, have loosely bound electrons that jump to other atoms
    • Something with a stronger hold of electrons can steal electrons from something with a weaker hold
    • Objects that have a stronger hold on electrons tend to be negative
    • Objects that have a weaker hold on electrons tend to be positive

 

 

 

 

  • Insulators: Materials that get in the way of the free flow of electrons from atom to atom and molecule to molecule. If charge is transferred to an insulator at a given location, the excess charge will remain at the initial location of charging. The particles of the insulator do not permit the free flow of electrons so the charge is not distributed evenly across the surface of an insulator
    • Examples:
      • Rubber
      • Glass
      • Wool

 

  • Conductors: Materials that permit electrons to flow freely from atom to atom and molecule to molecule. A conductor will allow charge to be transferred across the entire surface of the object due to electron movement. Since electrons are negative, they repel each other until the charge is distributed over the entire object
    • Examples:
      • Silver
      • Aluminum
      • Water
    • CONDUCTION:
      • When a charged and neutral object touch and the neutral object turns charged which makes the two object repel each other
      • If a charged object touches a neutral object, the neutral object becomes charged
      • Transfer of charges from the charged object to the uncharged object
  1. Initial charge; one is neutral, one is charged
  2. Both objects get the same charge
  3. Repel after gaining same charge (ex: balloon against wall after friction with hair)

 

  • INDUCTION:
    • Involves the movement of electrons in a neutral object when a charged object is brought close to the neutral object
    • NO DIRECT CONTACT
    • results in opposite charges (permanent)
    • rod → keeps the same charge, object → has the opposite charge (permanent)
    • 2 forms:
      • Temporarily Charge
        • no change in the number of electrons on the object, so object remains neutral
        • rod → stays same charge, object → stays neutral No grounding used
        • is not permanent, TEMPORARY!!!!
      • Permanently Charge
        • when temporarily charged object becomes grounded, it becomes permanent
        • results in opposite charges
        • rod → keeps the same charge, object → has the opposite charge Only when using grounding mechanism and after it gets removed
        • Grounding: a way for electrons to escape the object/way for excess electrons to be removed so a discharge won’t occur.

 

 

 

 

 

 

 

Electrostatic Series:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Current Electricity

Define: An electric current is a flow of electric charge. In electric circuits, this charge is often carried by moving electrons in a wire.

Conductors: Materials that allow the flow of electrons through them, can evenly distribute electrons

Insulators: Materials that do not allow the flow of electrons through them, keeps electrons in one place

Four parts of a circuit: Circuit is complete if it has all of these components

  • Source: Resources for electric power
    • Battery
  • Load: A device that transforms electrical energy into heat, motion, sound, or light
    • Lightbulb
    • Sound
    • Heat
  • Conducting Wires: A conductor that carries electricity over a distance
    • Copper wiring
    • Humans
    • Any conductor
  • Switch: A control device that either allows electrons to flow or stop it. It makes or breaks the current. It is not in every circuit
    • Push switches
    • Toggle switches

Circuits:

  • The electrons leave the negative side
  • To find the load, there needs to be the purpose (light, sound, or heat)
  • A closed circuit is connected together to let the electrons flow
  • An open circuit has a “break” that disrupts the flow
  • Circuit must be in a full loop
  • Mains electricity is more powerful than battery electricity
  • When the switch is in the off position, we consider the circuit broken
  • Series
    • Pathway for electrons to travel
  • Parallel circuit
    • More than one pathway for electrons to travel
  • 5V = 1 Cell

Circuit Symbols and names:

Voltmeter: Measures voltage (Not part of the circuit)

Ammeter: Measures electrical current

Motor: Wat u think a motor does. (used to help make pasta of course)

Buzzer: Produces buzzing sound (BROOM BRROOOMMM)

 

Electric Circuit Components

Battery (or Source):

  • Provides the energy for the electrons
  • The battery gives the electrons their energy by lifting them into a higher voltage

Conductor (wires):

  • Joins all the parts of a circuit.
  • Provides a pathway for electrons.
  • Allow the electrons to pass along without changing their energy

Switch:

  • Controls the flow of electrons
  • Open = off
  • Closed = on

Insulator:

  • Does not let electrons flow through
  • Holds onto them

Ammeter:

  • Counts the number of electrons passing by a point per second.

Voltmeter:

  • Counts the energy per electron
  • The voltmeter measures how much energy the electron lost while falling through light bulb or gained while raised through the battery

 Light Bulb:

  • Uses up energy from electron

 

 

 

 

Series Circuit:

  • Voltage is shared in series circuit
  • Current never changes anywhere in a series circuit
  • Joules measures the energy in the current (v) (volts= joules per coulomb) (energy= joules)
  • Current is the amount of electrons in the circuit

Parallel Circuit:

  • In a parallel circuit the voltage does not change while the amps are shared
  • a parallel circuit is basically more than one series circuits
  • when there is more bulb in a series than others, the brightness of the bulbs will be lowered
  • Voltage isn’t shared
  • Amps is shared

 

 

Ohm’s Law

Resistance, Current, Volts

  • R = Resistance
    • R = V/I
  • I = Current
    • I = V/R
  • V = Volts
    • V = R x I

Energy, Power, time

  • E = Energy (Joules)
    • P x t
  • P = Power (Watts)
    • E/t
  • t = time
    • E/P

 

Efficiency

  • Efficiency (%) = useful energy output (J or kJ) x 100%

                 total input energy (J or kJ)

 

kWh – Kilowatt hour

  • Multiply kw by the hour