Physics 003

• Electrostatics

  The branch of science that deals with the electrical phenomena that arises from stationary electric charges
• Electric charge

  Positive charge (+) and negative charge (-)
• Like charges repel each other, while unlike charges attract each other
• Charged objects


  • Glass rod
  • Plastic ruler
• The electric charge on the plastic ruler is called negative and that on the glass rod is called positive
• Coulomb's law

  In free space, oppositely charged bodies attract each other, while similarly charged bodies repel with a force that varies directly as the product of the magnitude of each charge and inversely as the square of the distance between them, the force being directed along the line joining the charges
• Permittivity of free space

  8.85 x 10^-12 C/N·m²
• According to Newton's third law of motion, the force on 1 due to 2 (f) is equal in magnitude to the force on 2 due to 1 (F), but the two forces act in opposite directions
• The net force on any charge will be the vector sum of the forces due to each of the other charges
• Electric field

  A region where a charged particle experiences an electric force
• Electric field lines originate from positive charges and terminate on negative charges
• Electric field lines do not touch or intersect one another
• Continuous charge distribution

  Dividing the charge distribution into small elements, each containing a small charge Δq, and calculating the electric field due to one element at a point P, then summing the contributions of all the charge elements
• Linear charge density

  Charge per unit length (C/m)
• Surface charge density

  Charge per unit area (C/m²)
• Volume charge density


  Charge per unit volume (C/m³)
• Motion of charged particles in a uniform electric field

  The acceleration of the particle is constant and in the direction of the electric field if positively charged, or opposite the electric field if negatively charged
• Work done on an object increases its kinetic energy, while work done against friction decreases it.
• Energy can be transferred from one object to another by work or heat
• The SI unit of energy is the joule (J)
• Electric potential difference between two points is defined as the amount of work done by an external agent to move a positive test charge from one point to another with respect to zero reference point.
• Kinetic Energy = ½ mv2
• Potential difference can be calculated using the equation V = W / q, where V is the potential difference, W is the work done, and q is the charge moved.
• The SI unit of power is watt (W) = Joules / second
• Power is defined as the rate at which energy is supplied or consumed
• A battery has a certain voltage that depends on the chemical reaction inside it.
• Potential Energy = mgh
• Potential difference = Work done / Charge moved
• Unit of electric potential difference is volt (V) where 1 V = 1 J/C
• SI Unit of Power is watt (W) - Joules per second