4.1 charge and current Flashcards
Charge
Measured in Coulombs (C), symbol is Q.
Elementary Charge
Smallest charge, e = 1.6 × 10^-19 C.
Current
Rate of flow of charge, symbol is I.
Amps
Unit of current, represented as A.
Base Unit for Current
Defined as As (Ampere-seconds).
Conductor
Material allowing charge flow, e.g., metals.
Electric Field
Region causing force on charged particles.
Conventional Current
Flow from positive to negative.
Drift Velocity
Average velocity of electrons in a conductor.
Number Density
Free electrons per cubic meter, symbol n.
Kirchoff’s First Law
Conservation of charge at junctions.
Potential Difference (p.d.)
Work done per unit charge, measured in JC^-1.
Electromotive Force (e.m.f.)
Energy per unit charge produced by a source.
Resistance
Opposition to current flow, measured in ohms (Ω).
Ohm’s Law
I is proportional to V at constant temperature.
Resistivity
Material’s opposition to electron flow, symbol ρ.
Temperature Effect on Resistance
Higher temperature increases resistance due to collisions.
Superconductors
Materials with zero resistivity below critical temperature.
Power
Rate of doing work, W = Pt.
Energy Bills
Charged in kilowatt-hours (kWh).
Voltmeter
Measures potential difference, placed in parallel.
Ammeter
Measures current, placed in series.
Current Equation
I = Anev, relates current, area, density, velocity.
Work-Energy Relationship
W = IVt, work done equals energy transferred.
Resistance Measurement
Calculated using potential difference and current readings.
