Electrostatics and Electromagnetism Flashcards
Electrostatics and Charge
Electrostatics: the study of charged particles in motion or at rest
Charge: an electrical property of a particle that creates attractive or repulsive forces; charge is either positive or negative- like repels like and opposite charges attract.
Coulomb and Fundamental Charge
Coulomb: the SI unit of charge Fundamental charge (e): the smallest amount of charge a particle can carry, equivalent to the charge of an electron; this is 1.6 x 10^-19 coulombs A proton carries an equivalent positive charge as an electron's negative charge, therefore, a molecule with an equal number of protons and electrons is electrically neutral.
Conductor and Insulator
Conductor: a material able to carry a charge b/c there are electrons that can be moved when an electrical potential is applied across point in the material. Metals are great conductors.
Insulator: the opposite of a conductor and resists the movement of charge b/c electrons are tightly bound, unlike the “cloud” of electrons surrounding most metals; common examples are glass, rubber, or ceramic.
Coulomb’s Law
Describe the forces between charged particles, called electrostatic force. This force is proportional to the strength of the two charges (q1 and q2), Coulomb’s constant (k=9x10^9 Nm^2/C^2), and inversely proportional to the square of the distance between the two charges.
Electrostatic force = k q1 q2 /r
Electric Field
exerts an electrostatic force on any charge within the field. An electric field is created by a point charge, and is strongest near the charge and weakens as the distance from the charge grows.
The strength of an electric field (E) is defined as the force that a test charge would feel at a given distance from the source of the field; this is simply calculated as E=kQ/r^2 where Q is the charge of the source of the electric field and r is the distance from the source
Electric Field Lines and Equipotential Lines
Electric field likes: represent the direction in which a positive charge would move within an electric field
Equipotential lines: concentric circles representing equivalent electric field strength around a charge source.
Electric Potential and Potential Energy
Electric potential (V): the amount of potential energy per unit charge within an electric field at a specified distance from the source of the charge: V=kQ/r. the potential is always the same at a given radius r.
Electric potential energy (EPE): defined as the amount of work required to bring a charged particle (q) from infinity to a certain point within an electric field and is calculated using the electric potential at that point: EPE = qV.
Potential Difference and Work of Electric Fields
Potential difference: the calculated change in electric potential (delta V) in moving a charge from one point to another within an electric field
Work done by an electric field is simply the change in potential energy in moving a charge within an electric field, calculated as the charge multiplied by the change in the electrical potential (V)
Current, Amperes, and Power
Current (I): the flow of charge moving across a potential difference; electrons are said to move from high (+) to low (-) potential in a circuit or electric system
Amperes are the SI unit of current
Current is defined as the amount of charge (q) moving through a conductor per unit of time (t): I = q/t
Power is work multiplied by time; in circuits it is the heat dissipated by a resistor or consumed by another device producing an electromotive force; P=IR^2 = IV
Electric Dipole and Dipole Moment
Electric dipole: results from the separation of a positive and negative charge by a short distance
Dipole moment (p): a vector expression of the strength and polarity (direction) of an electric dipole in terms of the product of the charges and the distance separating the charges (r): p = qr
Electric Flux and Permittivity
Electric flux: the electric field (E) multiplied by the area through which that field passes
Permittivity: a coefficient that describes how a material affects an electric field that passes through that material
Permittivity of free space = 8.85 x 10^-12 F/m
Gauss’s Law
The electric flux through a closed surface is equal to the charge enclosed (Q) by the surface divided by the permittivity of the material
Electromagnetic Induction and Electromotive Force
Electromagnetic induction: when a conductor is moved through a magnetic field, and electromotive force (EMF) is produced
The EMF created causes the movement of charge; the movement of charge is current.
Therefore, moving a wire (conductor) through a magnetic field induces a current in the wire
Magnetic Field and Magnetic Force
Magnetic field (B): a field that is created by moving charges or fixed magnets that can exert force on other charges or fixed magnets
Magnetic force: exerted perpendicular to a charge (q) moving with velocity (v) in a magnetic field (B)
Magnetic force = q v B sin (@)
Right-Hand Rule
Right-hand rule: describes the direction of the magnetic force vector that a moving charge experiences within a magnetic field (B) using the right hand and three orthogonal (mutually perpendicular) vectors:
Thumb points in direction of moving charge
Fingers point in direction of magnetic field
Palm faces in direction of magnetic force
