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30 Cards in this Set

  • Front
  • Back
Potential Drop
The work done on a unit charge as it is moved between two points in an electrical field; also called potential difference.
Ohm's Law
At a constant temperature, the current in a metallic conductor is directly proportional to the potential difference between its ends and inversely proportional to its resistance: V = IR.

Ohm's Law does not hold for semiconductors.
Tesla (T)
The SI unit of magnetic flux density (magnetic field intensity).

One tesla is equivalent to one weber per square meter or one newton per ampere-meter: 1T = 1 Wb/m2 = 1 N/A·m
Three-Variable Left Hand Rule
The direction of current flow, the magnetic field direction, and the direction of the electromagnetic force are all perpendicular to each other. If two of these variables are known, the third can be determined using this rule: Extend your left hand. Your thumb points in the direction of electron flow, your fingers point in the direction of the magnetic field, and your palm points in the direction of the force.
Electric Power
The time-rate at which electric energy is expended.

The watt, W, is the SI derived unit for electric power.
For conductors that obey Ohm’s Law: .
Electric power is a scalar quantity.
Compass
An instrument used for determining direction by means of a magnetic needle whose north pole points to the magnetic south pole of the Earth which is located at the geographic north pole.
Magnetic Field
Magnetic fields exist in areas around natural magnets and in regions around electric currents.

The direction of a magnetic field is, by convention, the direction in which the N-pole of a compass would point when placed in the field.
Conductor
A substance in which there are many free electrons because the outer electrons are not bound or are loosely bound to atoms.

For example, most metals are good conductors.
Electric Field
An electric field is said to exist in any region of space in which an electric force acts on a charge.

An electric field exists around every charged object.
The electric field intensity is a vector quantity.
The magnitude of the strength of an electric field at any point is the force per unit charge at that point in the electric field: E = F/q.
The direction of the field is given by the direction of the force acting upon a positive test charge.
Coulomb (C)
The SI unit of charge, approximately 6.3 1018 elementary charges (from the List of Physical Constants in the reference information).
Coulomb's Law
The electrical force between two point charges is directly proportional to the product of the charges, and inversely proportional to the square of the distance between them: .

In this relationship, the constant of proportionality, k, is called the electostatic constant.
Volt (V)
The SI unit of electric potential or potential difference.

A potential difference of 1 volt exists between two points if 1 joule of work is required to transfer 1 coulomb of charge between these two points against the electric field: V = W/q; 1 V = 1 J/C
Flux Density
A measure of magnetic field strength; the number of magnetic flux lines per unit area.

Flux density is a vector quantity.
The tesla, T, is the SI unit of flux density, equivialent to 1 weber per square meter = 1 newton per ampere-meter: 1 T = 1 Wb/m2 = 1 N/A×m.
Electric Potential
The electric potential at any point in an electric field is the work required to bring one coulomb of positive charge from infinity to that point: V = W/q.

Electric potential is a scalar quantity, measured in volts, V.
Electric Field Intensity
The rate at which electric potential changes with position in a uniform electric field.

The magnitude of the strength of an electric field at any point is the force per unit charge at that point in the electric field: E = F/q.
The volt/meter, V/m, is a unit for electric field intensity.
Resistance
Opposition to current flow offered by a conductor or semiconductor; the ratio between potential difference across and current in a conductor: R = V/I.

The ohm, Ω, is the SI unit of resistance: 1 Ω = 1 V/A.
Current
The amount of electric charge flowing past a specific point in a circuit for a unit of time.
Electric Energy
The energy used in an electric circuit is the product of the power developed and the time during which charge flows: W = Pt = VIt = I2Rt.

The derived unit joule, J, is the SI unit for electric energy.
Electric energy is a scalar quantity.
Equivalent Resistance
A single resistance that is equivalent to a set of resistances in a series or parallel circuit.
Two-Variable Left Hand Rule (Coiled Conductor)
A rule used to determine the direction of the magnetic field created by a current flowing in a coiled conductor. When the fingers of your left hand curl in the direction of current flow in a coil, your left thumb will point toward the induced north magnetic pole.
Electronvolt (eV)
The amount of energy required to move one elementary charge through a potential difference of one volt: 1eV = 1.6 × 10-19 J.
Parallel Circuit
A circuit in which there is more than one current path.

The potential drop is the same across each branch of a parallel circuit: Vt = V1 = V2 = V3 = … .
The total current in a parallel circuit is the current supplied by the source and is equal to the sum of the branch currents: It = I1 + I2 + I3 + … .
The reciprocal of the equivalent or total resistance of a parallel circuit is equal to the sum of the reciprocals of the branch resistances: .
Voltmeter
A high-resistance device used to measure the potential difference across two points in an electric circuit.

A voltmeter can be constructed by wiring a large resistor in series with a galvanometer.
The symbol for a voltmeter is:
Magnetic Flux Lines
A magnetic field is mapped by imaginary magnetic lines of force called flux lines.

The lines of force always form closed paths and never cross.
The magnitude of a magnetic field is greatest where the lines of force are closest together.
The direction of the magnetic field at any point is tangent to the field line at that point.
Galvanometer
A device used to measure weak electric current.

A galvanometer has a coil placed in a uniform field produced by a permanent horseshoe magnet.
The coil is free to rotate against a spring.
The degree of deflection of the coil is directly proportional to the current in the coil.
Watt (W)
The SI unit of power; a derived unit equivalent to one joule per second: 1 W = 1 J/s
Resistor
A device that offers resistance in an electrical circuit. The symbol for a resistor is:
Ampere (A)
The SI unit of electric current, defined as one coulomb of charge passing a point in one second: 1 A = 1 C/s
Grounding
The addition or removal of electrons to or from an object in order to neutralize its charge.
Mass Spectrometer
A device used to measure the masses of individual atoms.

An element in the gaseous phase is bombarded with electrons causing one or more electrons to be removed from the atoms of the element.
The resulting positive ions are subjected to magnetic and electric fields.
The charge-to-mass ratio of ions may be determined by measuring the radius of the circular path that the ions travel. If the charge of the ion is known, its mass can then be calculated.
Mass spectrometry is a common method of separating the isotopes of an element.