Electricity Flashcards
(24 cards)
What is electric current?
Flow of charged particles
What is the formula for charge?
Q = I × t
What does Q represent in Q = I × t?
Charge (Coulombs)
What is the definition of 1 Coulomb?
Charge flowing per second when 1 Ampere flows
Is charge quantised or continuous?
Quantised – only in multiples of elementary charge
What is the value of elementary charge (e)?
1.6 × 10⁻¹⁹ C
What is potential difference?
Work done per unit charge between two points
1 Volt equals how many Joules per Coulomb?
1 J/C
What is the formula for work done in electric circuits?
W = V × Q
What are the three formulas for electrical power?
P = VI, P = I²R, P = V²/R
What causes current in conductors?
Drift of electrons under potential difference
What is the equation for current using drift velocity?
I = nAvq
In the formula I = nAvq, what does each symbol mean?
n = number of electrons/m³, A = area, v = drift velocity, q = charge
What is resistance?
Ratio of potential difference to current
What is the formula for resistance?
R = V / I
What is the SI unit of resistance?
Ohm (Ω)
What is Ohm’s Law?
Current is proportional to voltage if temperature is constant
What is the formula for resistivity?
R = ρL / A
What does ρ (rho) represent?
Resistivity (Ω·m), a material property
What is the resistance behaviour of an ohmic conductor?
V/I constant, resistance stays the same
What happens in a filament lamp as voltage increases?
Temperature increases → resistance increases
What happens in a thermistor as temperature increases?
Resistance decreases
What is a diode’s characteristic?
Conducts in one direction only after threshold voltage
What happens to an LDR in high light?
Resistance decreases
