Electric Fields and Electric Energy

Electric Fields and Electric Energy

1. The Electric Field

   • The electric Field can be visualized
     • The Direction of an electric field is away from a positive charge and toward a negative charge.
   • Determining the Force on a Charge
     • The Electric Fore due to an Electric field
       • SI unit: N
   • The Electric Field is the amount of force per change
     • Magnit, Eude of the Electric Field, E
       • Magnitude of Electric Field= force on positive change/amount of charge
         • SI unit: N/C
   • Point Charge electric fields decrease with distance
     • Magnitude of the Electric field due to a point Change
   • Electric Fields add together
     • Applying Superposition
   • Some animals can produce and detect electric fields
   • Electric fields have distinctive shapes and patterns
     • Electric dipoles
       • Is defined as a couple of opposite charges q and –q separated by a distance d.
     • Infinite Plates and Parallel-Plate Capacitors
       • Infinite plates imply that the velocity does not vary along the width of the plates
       • A parallel plate capacitor is used to store a high amount of electric energy as they use two plates like electrodes.
   • Excess charge moves to a conductor´s outer surface
   • An Object can be charged without ever tuching it
     • Charging by Induction
       • Is a method used to charge an object without actually touching the object to any other charged object.

2. Electric potential Energy and Electric Potential

   • Electric potential energy
     • Electric potential energy Ue is the potential energy stored when charges are out of equilibrium (like gravitational potential energy).
   • Electric fields sotre mechanical work
     • Opposite Charges
       • Separating two charges that attract each other requires mechanical work. This work is stored in the electric field as electric potential energy.
     • Like Charges
       • Moving two charges that repel each other closer together requieres mechanical work. This work is stored in the electric field as electric potential energy.
   • Voltage is the electric potential energy per charge
     • Electric Potential
       • Change in Electric potential= change in electric potential energy/ charge
         • SI unit: joule/coulomb= Volt( V)
   • Units of Voltage
     • Volt
       • The standard unit of measurement used for the expression of voltage is volt which is represented by the symbol v. However, the volt is a derived SI unit of electric potential or electromotive force.
   • Electric Potential is related to the electric field
     • Connection between the Electric Field and the Electric Potential
       • Electric field= - Change in electric potential / distance
       • SI Unit: volts/meter (V/m)
   • Energy is conserved in electrical systems
     • General Equation for Energy Conservation
     • Applying Energy Conservation
   • Direction of Acceleration in an Electric Field
     • Positive Charges accelerate in the direction of dencreasing electric potential
     • Negative Charges accelerate in the direction of increasing electric potential
   • Electric potential decreases with distance
     • Electric Potential for a Point Charge
     • Electric Potential Energy for point charges q and q0
   • Electric Potentials combine by simple addition
     • The total electric potential due to two or more charges is equal to the algebraic sum of the potentials due to the individuals changes
   • Calculating Work Done in an Electric Field
     • The work done by the electric force is:
       • W= -qEd
     • The work done to move changes in an electric field and the systems change in electric potential energy:
       • ΔPE= -W or ΔPE=qED

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