sensing Flashcards
what is the definition for current?
current is the rate of flow of charge (units: amps, A)
what is an equation for current?
an equation for current is:
I = ΔQ / Δt
what is an equation for ΔQ (change in charge)?
an equation for ΔQ is:
ΔQ = Nq
where:
• N is the total number of charged particles
• q is the charge on one particle
what is 1 coulomb?
1 coulomb is the charge flowing through a point in one second when there is a current of 1A
units for charge: Coulomb, C
what is the definition of potential difference?
potential difference is the energy transferred per unit charge when moving between two points in a circuit
units: Volt, V
what is an equation for pd?
an equation for pd is:
V = ΔE / Q
or
V = W / Q
where:
• W is work done between two points (units: Joules, J)
pd == voltage
energy transfer == work done
what a an equation for work done?
an equation for work done is:
W = VIt
to help remember W = ItV (like ITV the tv channel)
what is resistance?
resistance is the measure of the difficulty of passing an electric current through a medium
units: Ohms, Ω
what are some equations for resistance?
some equations for R:
R = V / I
or
R = 1 / G
equations for resistance concerning resistors in circuit?
resistors in series:
R tot = R1 + R2 + R3 + …
resistors in parallel:
R tot = 1/R1 + 1/R2 + 1/R3 + …
what is conductance?
conductance is the measure of the ease of passing an electric current through a medium (so the opposite of resistance)
units: siemens, S
equations for conductance concerning conductors in circuit?
conductors in series:
G tot = 1/G1 + 1/G2 + 1/G3 + …
conductors in parallel:
G tot = G1 + G2 + G3 + …
what are some equations for conductance?
some equations for conductance are:
G = I / V
or
G = 1 / R
V = IR
what is Ohm’s law?
⋅ Ohm’s law states that the voltage across a component is proportional to the current through it, ⋅ V = IR
what is heat dissipation?
⋅ heat dissipation is the thermal energy transfer per second resulting in an increase in energy of the surroundings
⋅ heat dissipation is measured in watts, W
how does heat dissipation occur?
⋅ heat dissipation occurs when:
1) electrons are accelerated by a pd, their movement is obstructed by the metal cations in the wire
2) the potential energy lost does work on the wire, heating it up
equation for heat dissipation:
what is the relationship between heat dissipation-R and heat dissipation-G
⋅ heat dissipation increases with increased R, TE transfer ∝ R
⋅ heat dissipation decreases with increased G, TE transfer ∝ 1/G
features of parallel circuits?
some features of parallel circuits are:
⋅ same pd [/ V] all around the circuit
⋅ different I around the circuit, split over each branch in inverse proportion to R (R1:I1 = R2:I2)
⋅(for multiple components on branches, add the resistances in series for each branch and then add the total resistance of each branch in parallel) (total R of parallel circuit always > lowest individual R)
features of series circuits?
some features of series circuits are:
⋅ different pd, split over each component in proportion to R (V1:R1 = V2:R2)
⋅same I all around the circuit
what is Kirchhoff’s First Law?
⋅ Kirchhoff’s First Law states that ‘the sum of the current entering an electrical junction equals the sum of the current leaving the junction’
⋅ Iin = Iout
what is Kirchhoff’s first law based on?
⋅ Kirchhoff’s first law is based on the conservation of charge
what is Kirchhoff’s Second Law?
⋅ Kirchhoff’s Second Law states that ‘the sum of all the potential differences and emfs across all of the components in a closed loop must be equal to zero’
⋅ PDtotal + EMFtotal = 0
what is Kirchhoff’s second law based on?
⋅ Kirchhoff’s second law is based on the conservation of energy.
what does Kirchoff’s law then also mean? (given that PDtotal + EMFtotal = 0)
⋅ given that PDtotal + EMFtotal = 0, Kirchhoff’s second law then also means that
EMFtotal = -PDtotal
⋅ (negative PDtotal bc voltage drops across circuit)
what side is the negative terminal?
⋅ the short and bold side is the negative terminal
what side is the positive terminal?
⋅ the long and thin side is the positive terminal
what does the I-V graph for an ohmic resistor look like?
⋅ the I-V graph for an ohmic resistor is a proportional, linear line through the origin
what does the I-V graph for a filament lamp look like?
