Physics: Electricity and Energy

Physics: Electricity and Energy

1. The Atomic Model, Electrical Charge Carriers and Electrostatics

   • The Atomic Model is made up of Protons, Neutrons and Electrons
     • Neutrons give off a Neutral charge
     • Protons give off a Positive charge
     • Electrons give off a Negative charge
     • These are called atoms
       • Opposites attract
       • Same repel
   • When objects rub together, this is called Electrostatics
     • This is how a Van Der Graff works
     • For example, a photocopier

2. Electrical Current

   • Electrons are free to move within a conductor
   • Electrons move to the positive side of a circuit. This is how a D.C. circuit works
   • The flow of electrons is known as the current
     • The size of the current is the amount of charge going through it
   • The current (I) formula
     • Q=IT
   • An A.C. current means that electrons do not go in one direction. They move forward and back constantly
   • The rate of changing direction is the frequency
     • UK frequency is 50Hz

3. Potential Difference (voltage) and Electric Fields

   • The greater the potential difference, the faster the rate of the electrons

4. Ohm's Law

   • Ohm's Law introduces Resistance
     • The higher the resistance, the lower the voltage
     • Resistance is measured in Ohms (Ω)
     • The Resistance formula id V=IR

5. Electrical Circuits

   • Components connected in series follow along a single path
     • The current is the same throughout the whole circuit
     • The voltage is split between each component depending on how much voltage each needs
       • The total voltage can be found by adding the voltage of each component together
     • The resistance can be found by adding each components resistance together
   • Components connected in parallel splits along the path somewhere
     • The current that flows into a path is the same when it flows out
     • The voltage is the same across every component
     • The total resistance is the resistance of each component added together under one
   • The Ring Circuit
     • This is a method that has all plugs connected to each other and the power supply in parallel and in series
       • This allows thinner cables
       • This allows the sockets to be anywhere on the circuit
       • It doesn't require a high current

6. Electronic Circuits

   • Digital Output Devices
     • Buzzer
       • Electrical > Kinetic/Sound
     • Solenoid
       • Electrical > Kinetic
     • LED
       • Electrical > Light
     • Relay
     • 7-segment display
     • Bulb
       • Electrical > Light/Heat
     • A device that gives an output using a D.C. circuit
   • Analogue Output Devices
     • Motor
       • Electrical > Kinetic/Sound
     • Loudspeaker
       • Electrical > Sound
     • A device that gives an output using an A.C. circuit
   • Input Devices
     • Microphone
       • Sound > Electrical
     • Solar Cell
       • Light > Electrical
     • Thermocouple
       • Heat > Electrical
     • A device that takes in an input and converts it to electrical energy

7. Electrical Power and Energy

   • The Relationship between power and electrical energy
     • E=Pt
   • The Relationship between power and current
     • P=IV
     • This is used to see what type of fuse is required
       • If the wrong fuse is fitted, it could cause it to overheat, which could cause a fire
         • P=IV+V=IR
           • P=(IxI)R
           • P=(VxV)/R
   • Paying for Electricity
     • This is measured in units
       • 1 unit = 1kW
         • This comes from the formula E=Pt
   • Power stations create power in four main steps
     • 1. Burn the fuel
       • 2. The steam generated from this causes the turbines to move
         • 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

8. Conservation of Energy

   • E=Fd
     • E=Energy (Work Done)
     • F=Force
     • d=Distance
   • Gravitational Potential Energy
     • Someone may be measuring by height and not distance
       • E=Fh
   • When someone may want to know the 'work done' when an object moves vertically
     • E=mgh
   • When kinetic energy is involved
     • E=1/2m(vxv)
   • When wanting to know the loss of energy
     • Ep=Ek
       • mgh=1/2m(vxv)
   • Efficiency
     • Not everything is 100% efficient
       • There is a way of measuring a variables efficeincy