static electricity

Examples of static electricity in the following topics:

• Static Electricity, Charge, and the Conservation of Charge

  • Electric charge is a physical property that is perpetually conserved in amount; it can build up in matter, which creates static electricity.
  • In physics, charge conservation is the principle that electric charge can neither be created nor destroyed.
  • Static electricity is when an excess of electric charge collects on an object's surface.
  • Static electricity can also be created through friction between a balloon (or another object) and human hair (see ).
  • Formulate rules that apply to the creation and the destruction of electric charge

• Charge Separation

  • Charge separation, often referred to as static electricity, is the building of space between particles of opposite charges.
  • Because electrons are labile (i.e., they can be transferred from atom to atom) it is possible for the phenomenon of "charge separation" (often referred to as static electricity) to occur.

• Electrostatic Shielding

  • Electrostatic shielding is the phenomenon that occurs when a Faraday cage blocks the effects of an electric field.
  • Electrostatic shielding is the phenomenon that is observed when a Faraday cage operates to block the effects of an electric field.
  • This type of cage was first invented by Michael Faraday in 1836, and can block external static and non-static electric fields.
  • When an external electric field operates on a Faraday cage, the charges within the cage (which are mobile, as the cage is a conductor) rearrange themselves to directly counteract the field and thus "shield" the interior of the cage from the external field
  • Faraday cages are limited in their effectiveness, and cannot block static and slowly varying magnetic fields, such as that of the planet Earth.

• Principles of Electricity

  • When a neuron is stimulated, an electrical impulse is generated and conducted along the length of its axon.
  • Voltage is equal to the work that would have to be done per unit charge to move the charge between two points against a static electric field.
  • The flow of electrical charge from one point to another is called current.
  • In the body, electrical currents reflect the flow of ions across cell membranes.
  • In electrically active tissue, the potential difference between any two points can be measured by inserting an electrode at each point and connecting both electrodes to to a specialized voltmeter.

• Conductors and Fields in Static Equilibrium

  • In the presence of charge or an electric field, the charges in a conductor will redistribute until they reach static equilibrium.
  • If conductors are exposed to charge or an electric field, their internal charges will rearrange rapidly.
  • It should be noted that the distribution of charges depends on the shape of the conductor and that static equilibrium may not necessarily involve an even distribution of charges, which tend to aggregate in higher concentrations around sharp points.
  • This occurrence is similar to that observed in a Faraday cage, which is an enclosure made of a conducting material that shields the inside from an external electric charge or field or shields the outside from an internal electric charge or field.
  • Describe behavior of charges in a conductor in the presence of charge or an electric field and under static equilibrium

• Overview of Electric Current

  • The firing of neurons in your brain is also an example of electric current - that is, the movement of electric charge through a conductive medium.
  • In equation form, electric current I is defined to be
  • Unlike static electricity, where a conductor in equilibrium cannot have an electric field in it, conductors carrying a current have an electric field and are not in static equilibrium.
  • An electric field is needed to supply energy to move the charges.
  • (a) A simple electric circuit.

• Dipole Moments

  • The electric dipole moment is a measure of polarity in a system.
  • Among the subset of electric dipole moments are transition dipole moments, molecular dipole moments , bond dipole moments, and electron electric dipole moments.
  • For the purposes of this atom we will focus on a broad overview of electric dipole moment in static situations.
  • Torque (τ) can be calculated as the cross product of the electric dipole moment and the electric field (E), assuming that E is spatially uniform:
  • Relate the electric dipole moment to the polarity in a system

• Electric vs. Magnetic Forces

  • Recall that in a static, unchanging electric field E the force on a particle with charge q will be:
  • It should be emphasized that the electric force F acts parallel to the electric field E.
  • The curl of the electric force is zero, i.e.:
  • A consequence of this is that the electric field may do work and a charge in a pure electric field will follow the tangent of an electric field line.
  • The electric field is directed tangent to the field lines.

• Relation Between Electric Potential and Field

  • Thus, the electric potential is a measure of energy per unit charge.
  • In terms of units, electric potential and charge are closely related.
  • In a more pure sense, without assuming field uniformity, electric field is the gradient of the electric potential in the direction of x:
  • The presence of an electric field around the static point charge (large red dot) creates a potential difference, causing the test charge (small red dot) to experience a force and move.
  • Explain the relationship between the electric potential and the electric field

• The Production of Electromagnetic Waves

  • Electromagnetic waves are the combination of electric and magnetic field waves produced by moving charges.
  • Once in motion, the electric and magnetic fields created by a charged particle are self-perpetuating—time-dependent changes in one field (electric or magnetic) produce the other.
  • This means that an electric field that oscillates as a function of time will produce a magnetic field, and a magnetic field that changes as a function of time will produce an electric field.
  • Placing a coin in contact with both terminals of a 9-volt battery produces electromagnetic waves that can be detected by bringing the antenna of a radio (tuned to a static-producing station) within a few inches of the point of contact.
  • Notice that the electric and magnetic field waves are in phase.