sensing Flashcards
how are most sensors powered?
SENSING
many sensors are powered using electricity
how do electronic sensors work? (simple)
SENSING
1) when using electronic sensors, any change in whatever the sensor is detecting will change the current in the connected circuit
2) the current is then processed to give a reading
what is current and its units?
SENSING
current is the rate of flow of charge[-d particles]
units: Amperes or Amps, A
you can also think of current as the measure of the number of charged particles that move past a point in a wire in a given time
what is the equation for current?
SENSING
I = ΔQ/Δt
what apparatus do you use to measure the current flowing through a part of a circuit, and what is its circuit symbol?
SENSING
you use an ammeter to measure the current flowing through a part of the circuit
the circuit symbol for an ammeter is:
what is the unit for charge and its symbol?
SENSING
the unit for charge is coulomb, C
1 coulomb is the amount of charge that passes a point in the circuit in 1 second when the current is 1 ampere
the symbol for charge is: Q
what is the conventional current and in what direction does it flow?
SENSING
conventional current is the direction scientists thought current flowed before discovering current is usually caused by the flow of electrons
conventional current flows from the positive terminal to the negative terminal of a power supply
what direction does unconventional current flow?
SENSING
unconventional current flows from the negative terminal to the positive terminal of a power supply
(unconventional current is how current actually flows in reality)
why does current actually flow via unconventional current
SENSING
current flows from the negative terminal to the positive terminal bc:
⋅ electrons are negatively charged
⋅ as opposites attract, this means electron will flow to positive terminal
what is the relationship between conventional current and electron flow?
SENSING
conventional current flows in the opposite direction to electron flow
what is potential difference, its symbol and its units?
SENSING
potential difference is the energy converted[/energy transferred/work done] per unit charge moved from one point in a circuit to another
units: Volts, V
what do you need to make electric charge flow through a conductor?
SENSING
to make electric charge flow through a conductor, you need to do work on the charge
what is the equation for potential difference?
V = ΔE/Q
or
V = W/Q
where
V = voltage or potential difference (they’re interchangeable)
E = energy transferred in moving charge
W = work done in moving charge
Q = charge
what is 1 volt?
SENSING
1 volt = when you convert 1 joule of energy in moving 1 coulomb of charge through a component
what apparatus is used to measure voltage[/pd] and what is its circuit symbol?
SENSING
a voltmeter is used to measure voltage[/pd]
the circuit symbol for a voltmeter is:
where should a voltmeter be connected in a circuit and why?
SENSING
a voltmeter should be connected in parallel with the component you’re investigating the pd across
• this is bc the pd across components in parallel is the same
• so when the voltmeter is connected in parallel to the component, both the component and the voltmeter experience the same pd across them
are potential difference and voltage usually interchangeable?
SENSING
yes
how do you describe the pd and the current for a certain component?
SENSING
⋅ there is a potential difference ACROSS the component
⋅ there is a current flowing THROUGH the component
what is power, its symbol and its units?
SENSING
power is the rate of the transfer of energy (or rate of work done bc work done == energy transfer)
the symbol for power is P
the units for power is: Watts, W or Joules per second, J s^-1
what is 1 watt equal to?
SENSING
1 watt = 1 joule per second
what is the equation for power?
SENSING
P = W/t
or
P = E/t
where:
P = power
W = work done
E = energy transferred
t = time
what is the equation for power in ELECTRICAL CIRCUITS?
SENSING
P = IV
where:
P = power
I = current
V = voltage
how can you explain the equation P = IV
SENSING
P = IV is explained by the fact that:
⋅ pd is the energy transferred per coulomb [moved…]
⋅ current is the number of coulombs transferred per second
⋅ so therefore pd x current is the energy transferred per second, i.e. power
I x V = E/Q X Q/t = E/t (bc Qs cancel out)
what makes it easier when calculating energy?
SENSING
• energy is easy to calculate if you know the power
• bc P = E/t