Circuits Vocab Flashcards
Current
Rate of flow of electrical charge around a circuit
I = Q/t
Units of ampere (A)
Charge
Physical property of matter that allows it to experience a force when placed in an electromagnetic field
Q = It
Units of coulomb (C)
Charge on one electron is 1.6 x10-¹⁹ C
5 x10¹⁸ electrons per C
Metals
Good conductors as lattice structure of positive ions creates a sea of free moving electrons
Potential difference
Potential energy difference per coulomb charge of electricity downhill round a circuit
pd = E/Q
Units of JQ-¹ (or Volts (V))
Cells
Chemical reactions inside push electrons out of negative terminal and consumes them at positive end, provides energy to “lift up” the electrons, hence the hill analogy
Energy provided to charges is spent around the circuit
Emf (electromotive force)
Electrical energy CREATED per unit charge, refers to source of electrical charge
Power
Rate of work done (energy)
P = E/t or P = FD/s
P = VI
Units of Watts (W)
Resistance
Ratio of pd per current for a circuit component
R = V/I
Units of ohms (Ω)
Conductance
Ratio of current per pd for a circuit component
G = I/V or G = 1/R
Units of siemens (S)
Resistivity
Factor of the resistance that takes into account the nature of the material
R = pL/A so p = RA/L
Units of ohm meters (Ωm²/m (Ωm))
Conductivity
Factor of conductance that takes into account the nature of the material
Inverse of resistivity
σ = 1/p or σ = GL/A
Units of siemens per metre (Sm/m² (Sm-¹))
Series
Current same everywhere
Voltage adds to sum at cell
Resistance adds to total
Conductance adds as inverse totals
Parallel
Current adds to total
Voltage same everywhere
Resistance adds as inverse totals
Conductance adds to total
Current, voltage and resistance
I = V/R
