Units and formulas Flashcards
Frequency is measured in what unit? What is the formula for frequency?
hertz(Hz)
s-1
Force is measured in what unit? What is the formula for force?
Newton, N
kg * m/s2
Energy/work is measured in what unit? What is the formula for energy/work?
Joules (j)
N*m
Power is measured in what unit? What is the formula for power?
Watts (W)
J/s
also
P = Vi (voltage*current)
Electric charge is measured in what unit? What is the formula for electric charge?
Coulomb (C)
A*s
Electric potential is measured in what unit? What is the formula for electric potential?
Volts (V)
J/C
Electric resistance is measured in what unit? What is the formula for electric resistance?
ohm(Ω)
V/A
Electric conductance is measured in what unit? What is the formula for electric conductance?
siemens(S) - mathematical symbol is G
A/V
What do the following letters symbolise?
V =
W =
q & Q =
i =
t =
P =
V = voltage in volts
W = the energy (work) in joules
q & Q = the charge in Coulombs (intantaneous - q) (static charge - Q)
i = current measured in Amps
t = time in s
P = power measured in Watts
What is the difference beteween positive and negative power?
Energy that is dissipated (lost) is considered positive.
e.g. a 60W lightbulb dissipates that energy, but is considered a positive wattage.
What is the equation for voltage (V)?
V = iR
What is the equation for current (i)?
i = V/R
What is the equation for Power (W)?
W = iV
What is the equation for Resistance (Ω - ohms)?
Ω = V/A
or
Ω = pl / A
where p = resistivity of the material
l = length of the material
A = area (cross sectional area)
If V = iR and P = iV, how else could P be calculated in relation to R?
V = iR
P = iV
so
P =i*(iR) = i2R = V2/R