Current Electricity Flashcards
What is Conventional Current? (used in syllabus)
Conventional current assumes that positive charges flow out of positive terminal, through circuit and into negative terminal of source
What is Electron Flow?
Electron flow is what actually happens, electrons flow out of negative terminal, through circuit and into positive terminal of source
Current Formula
I=Q/t
What is Current measured using?
Ammeter
What is a battery?
A source of energy that enables charges to be forced around a circuit.
What is an Electromotive Force (emf)?
The work done by the source in driving a unit charge around a complete circuit
Emf Formula
E=W/Q
Combined emf in series
Combined emf is x+x+x
Combined emf in parallel
Combined emf is x
What is Potential Difference?
The work done to drive a unit of charge through the component
P.d Formula
V=W/Q
What is Resistance?
Resistance is a measure of a material’s opposition to flow of electric charge.
Defined as the ratio of p.d (V) across it to the current (I) through it
What is P.d measured using?
Voltmeter
Resistance Formula
R=V/I
Common resistance components
Carbon resistors, LDR, Variable resistors
What is Ohm’s Law?
States that current in a conductor is directly proportional to p.d
What are Ohmic Conductors?
Ohmic conductors are materials that obey ohm’s law (constant gradient graph)
What are Non-Ohmic Conductors?
Non-ohmic conductors are materials that do not obey ohm’s law (increasing gradient graph)
What are some factors that affect resistance?
Temperature, length, cross-sectional area and resistivity
Resistivity Formula
R=p(l/A)
