Chapter 26 Concepts - Current & Resistance Flashcards
Define electric current (I).
Charges in motion; units: 1 Coulomb/second= 1 Ampere (A)
What is the Current Junction Rule?
Due to conservation of charge, the magnitudes of currents in branches of a junction add to yield the magnitude of the original current.
Define charge carriers
positively charged particles forced to move through a loop by the electric field
Define current density (J)
the flow of charge through a cross-section of the conductor at a particular point; units: 1 Ampere/meter^2= 1 A/m^2
Discuss the directionality of current density
If charges are positive, it follows the direction of potential difference
If charges are negative, it opposes the direction of potential difference
Define drift speed (v_d)
opposes the direction of the applied electric field that causes the current
How does carrier charge density (ne), current density (J), and drift speed (v_d) relate?
For a positive carrier, ne is positive and J and v_d have the same direction
For a negative carrier, ne is negative and J and v_d have opposite directions
Define resistance
the ratio of potential difference and current; units: 1 Volt/Ampere = 1 Ohm
Discuss the difference between resistance and resistivity
Resistance (units: ohm) is a property of an object while resistivity (units: ohm-meter) is a property of a material
Define Ohm’s Law
Current through a device is ALWAYS directly proportional to the potential difference applied to the device
What is an ohmic device/material?
A device’s resistance is independent of its current or potential difference
A material’s resistivity is independent of its electric field
define superconductivity
charge can flow through a conductor without losing its energy to thermal energy
