3- Sensing Flashcards
Current,I definition?
The rate at which charge flows through a point in an electrical circuit.
I= Q/t
Kirchoff’s first law?
At any electrical junction, the total current into a junction is equal to the total current out.
Potential difference definition, V?
The energy transfer per unit of charge travelling between two points in a circuit.
Power definition?
The rate at which energy is transferred (Js^-1) or (W)
What is Ohm’s law?
At a constant temperature, the current flowing through a resistor is proportional to the potential difference.
What is conductance, G? Units?
The ratio of current over Voltage, measured in Siemen.
Equation of G tot and R tot, and I tot in parallel
G = G1 + G2 +…
I = I1 +I2 +…
1/R= 1/R1 +1/R2 +…
Equations for I, G and R in series?
Current is constant throughout.
1/G= 1/G +1/G +…
R= R + R +…
Summary of parallel?
P.d
Current
G/R ?
P.d same
Current shared
Cunductances add
Summary of Series?
P.d
Current
G/R?
P.d shared
Same current
Resistances add
When investigating I-V characteristics for components, how can you minimise uncertainty?
Take readings at more voltages and use ammeters and voltmeters with greater resolution.
Equation linking resistance and resistivity?
R=ρL/A
What is the Equation linking Conductance and Conductivity?
G=σA/L
Define a semiconductor
A material midway in electrical conductivity and resistivity between conductors and insulators.
Define number density, n.
The number of mobile charge carriers per unit volume of the conductor. Measured in m^-3.
Define drift velocity.
The mean velocity of charge carriers in a conductor carrying an electrical current.
Explain why semiconductors increase in conductivity as temperature increases.
More electrons get excited and move from the valance band into the conduction band.
What is a sensor circuit?
A circuit whose electrical properties depend on environmental variables and can be used to monitor or measure those variables.
What is emf?
The energy per unit charge given by any source of electrical supply to the charges set in motion.
What is Kirchoff’s second law?
For a complete circuit, the sum of the emf is equal to the sum of the pd’s across the resistances of the circuit.
Define internal resistance
Resistances within a source of emf, resulting in a drop of terminal pd when a current is drawn from the source.
