Physics: Electricity and Energy

The Atomic Model, Electrical Charge Carriers and Electrostatics
1. The Atomic Model is made up of Protons, Neutrons and Electrons
  1. Neutrons give off a Neutral charge
  2. Protons give off a Positive charge
  3. Electrons give off a Negative charge
  4. These are called atoms
    1. Opposites attract
    2. Same repel
2. When objects rub together, this is called Electrostatics
  1. This is how a Van Der Graff works
  2. For example, a photocopier
Electrical Current
1. Electrons are free to move within a conductor
2. Electrons move to the positive side of a circuit. This is how a D.C. circuit works
3. The flow of electrons is known as the current
  1. The size of the current is the amount of charge going through it
4. The current (I) formula
  1. Q=IT
5. An A.C. current means that electrons do not go in one direction. They move forward and back constantly
6. The rate of changing direction is the frequency
  1. UK frequency is 50Hz
Potential Difference (voltage) and Electric Fields
1. The greater the potential difference, the faster the rate of the electrons
Ohm's Law
1. Ohm's Law introduces Resistance
  1. The higher the resistance, the lower the voltage
  2. Resistance is measured in Ohms (Ω)
  3. The Resistance formula id V=IR
Electrical Circuits
1. Components connected in series follow along a single path
  1. The current is the same throughout the whole circuit
  2. The voltage is split between each component depending on how much voltage each needs
    1. The total voltage can be found by adding the voltage of each component together
  3. The resistance can be found by adding each components resistance together
2. Components connected in parallel splits along the path somewhere
  1. The current that flows into a path is the same when it flows out
  2. The voltage is the same across every component
  3. The total resistance is the resistance of each component added together under one
3. The Ring Circuit
  1. This is a method that has all plugs connected to each other and the power supply in parallel and in series
    1. This allows thinner cables
    2. This allows the sockets to be anywhere on the circuit
    3. It doesn't require a high current
Electronic Circuits
1. Digital Output Devices
  1. Buzzer
    1. Electrical > Kinetic/Sound
  2. Solenoid
    1. Electrical > Kinetic
  3. LED
    1. Electrical > Light
  4. Relay
  5. 7-segment display
  6. Bulb
    1. Electrical > Light/Heat
  7. A device that gives an output using a D.C. circuit
2. Analogue Output Devices
  1. Motor
    1. Electrical > Kinetic/Sound
  2. Loudspeaker
    1. Electrical > Sound
  3. A device that gives an output using an A.C. circuit
3. Input Devices
  1. Microphone
    1. Sound > Electrical
  2. Solar Cell
    1. Light > Electrical
  3. Thermocouple
    1. Heat > Electrical
  4. A device that takes in an input and converts it to electrical energy
Electrical Power and Energy
1. The Relationship between power and electrical energy
  1. E=Pt
2. The Relationship between power and current
  1. P=IV
  2. This is used to see what type of fuse is required
    1. If the wrong fuse is fitted, it could cause it to overheat, which could cause a fire
      1. P=IV+V=IR
        P=(IxI)R
        P=(VxV)/R
3. Paying for Electricity
  1. This is measured in units
    1. 1 unit = 1kW
      1. This comes from the formula E=Pt
4. Power stations create power in four main steps
  1. 1. Burn the fuel
    1. 2. The steam generated from this causes the turbines to move
      1. 3. This turns a generator which then creates electricity
        4. This is sent to a 'step-up' transformer which highly increases the voltage sent across the power lines
        The reason for the high increase in voltage is to minimise the current, which then generates less heat
        The voltage is taken back down to 230V at the 'step-down' generator found near houses
Conservation of Energy
1. E=Fd
  1. E=Energy (Work Done)
  2. F=Force
  3. d=Distance
2. Gravitational Potential Energy
  1. Someone may be measuring by height and not distance
    1. E=Fh
3. When someone may want to know the 'work done' when an object moves vertically
  1. E=mgh
4. When kinetic energy is involved
  1. E=1/2m(vxv)
5. When wanting to know the loss of energy
  1. Ep=Ek
    1. mgh=1/2m(vxv)
6. Efficiency
  1. Not everything is 100% efficient
    1. There is a way of measuring a variables efficeincy

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