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59 Cards in this Set
- Front
- Back
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Describe a Wave |
A wave is a disturbance that travels through a medium from one location to another, transferring energy along the way. |
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Outline Wave Characteristics |
Amplitude Wave Length Wave Speed |
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Describe Transverse Wave Motion |
Medium particles move at 90 degrees to direction of wave travel Typically seen as Sine or Cosine wave Causes peaks and troughs |
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Describe Longitudinal Motion |
Medium particles move parallel to the waves direction of travel Causes compressions and rarefactions Same characteristics as a Transverse Wave (amplitude, wavelength, wave speed etc) |
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Define Amplitude |
The amount of displacement from rest that the wave Motion causes in the medium. Also a measure of the power of the wave. |
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Define Wavelength |
Defined as the distance between the maximum, or minimum points of displacement of the medium that the wave is moving through (the distance before the wave Motion repeats itself) |
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Define Wave Period |
The time measured in seconds, required for a point in the medium to complete one full cycle of its motion - from its highest point to its lowest, and back again. Relates to how fast the wave moves through the medium. |
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Define Frequency |
The number of wave cycles passing a point in a given time (normally one second) |
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Define Wave Speed |
Described how fast the wave is travelling through the medium. Wave speed is controlled by the medium itself. |
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Define a Point Source |
An infinitely small, theoretical location where something (a wave) is said to have come from. Used to predict what would happen in the 'real world' |
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Define Wave Interference |
Occurs when two waves travelling in the same medium interact with each other, forming a resultant wave. |
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Define Beat Frequency |
Two waves very close in frequency and amplitude Start out in phase, creating constructive interference Over time become out of phase, resulting in deconstructive interference Final result has another wave superimposed on the combination |
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Define Harmonics |
They are (whole number) multiples of the fundamental wavelength. |
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Define Fixed End Reflection |
Going from a less dense to a more dense medium |
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Define Free End Reflection |
Going from a more dense to a less dense medium |
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Define Refraction |
When a wave Motion passes into a different medium at an angle. The wave essentially 'bends' |
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Outline 3 Ways That Demagnetisation Occurs |
Electromagnetism Shock Heating |
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What are Meridians? |
Meridians are lines of magnetic flux |
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What is magnetic variation? |
The angle between true and magnetic meridians (difference between mag/true North) |
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Name 3 Ways to increase the field in a solenoid |
Increase current Increase number of coils Adding a soft iron core |
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The angle that magnetic lines of force make with the earth's surface is called? |
Magnetic Dip |
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Describe Ohm's Law |
In a DC circuit, current is directly proportional to the voltage and inversely proportional to the resistance |
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Describe the basic principle of an LCD display |
The ability of two polarising filters to change orientation under electrical control which modifies the transmission of reflected light (or backlight) through the material to cause patterns to be displayed |
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Describe 4 properties of an EM wave |
E and M fields are at 90 degrees to each other No supporting medium required Can be reflected, refracted or diffracted Will suffer attenuation |
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From what frequency do space waves occur? |
40MHz and above |
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State the 8 frequency bands and their frequency range |
VLF - 3-30kHz LF - 30-300kHz MF - 300kHz-3MHz HF - 3-30MHz VHF - 30-300MHz UHF - 300MHz-3GHz SHF - 3-30GHz EHF - 30-300GHz |
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Name the four types of modulation |
Amplitude Frequency Pulse Phase |
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List the 4 characteristics of a receiver |
Sensitivity Selectivity Stability Fidelity |
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What does RADAR stand for and what does it do? |
Radio Detection and Ranging - determines presence, position or motion of an object using EM waves |
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State and define the two main classes of RADAR |
Pulse - shorted pulses of radiation emitted at x time intervals in order to determine position of object. Continuous RADAR - emits continuous radiation using a variation in frequency of transmissions to distinguish between echoes. |
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Lost advantages and disadvantages of Pulse RADAR (4) |
Advantages: high peak power from low average power output Range finding One aerial for rx/tx Disadvantage: Doesn't distinguish between stationary and moving targets immediately |
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List advantages (3) and disadvantages (4) of Continuous Wave RADAR |
Advantages: Identify moving targets easily High mean power = greater range Less complex equipment Disadvantages: No range with basic system Tx/rx aerials required Precaution required to ensure direct reception doesn't occur Can only handle small number of targets |
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Lost 4 variables associated with lower RADAR frequency bands |
Increased resolution and precision weight Reduction in equipment size and weightReduction in power and rangeIncreased interference Reduction in power and range Increased interference |
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Name 5 types of RADAR |
Search Mapping Doppler Identification Tracking |
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Name the RADAR display used by ATC |
Plan Position Indicator (PPI) |
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What is the difference between primary and secondary RADAR? |
Primary RADAR relies on reflected energy from the target to reach the tx/rx station. Secondary RADAR has the target being interrogated, and transmits a signal in return |
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List 2 fundamental properties of a gyroscope |
Rigidity Procession |
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Describe the basic Gyroscope construction |
A rotor spinning around its spin axis Rotates around 1 or more axes using gimbals One or two degrees of freedom |
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List 6 advantages of a Ring Laser Gyro |
Unaffected by high G's Absence if moving parts Rapid turn on Cheaper Direct digital output Insensitive to local environment |
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Name 4 applications of gyroscopic knowledge |
Attitude indicator Gyro compass systems Turn and slip indicators Inertial Navigation Systems (INS) |
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Outline 4 factors affecting conduction |
Temperature gradient Cross sectional area Overall length Material properties |
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What is temperature defined as? |
The thermal state of a material |
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What is heat defined as? |
Heat is the energy transferred between matter |
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Define Specific Heat |
Ratio of heat required to change the temperature of 1kg of a material by 1 degree C, compared to 1kg of water |
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Define Super Cooling |
A liquids ability to be cooled below it's freezing point, whilst still remaining in liquid form, under certain conditions. |
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State the 3 state variables for an ideal gas |
Absolute Pressure (P) Volume (V) Absolute Temperature (T) |
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State Boyles Law |
Pressure and Volume are inversely proportional when it is a fixed amount of ideal gas, at a fixed temperature. |
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Define Charles' Law |
The volume of a given amount of gas is directly proportional to its absolute temperature. |
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Define stress on a body |
When a body is being acted on by a force |
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Define strain on a body |
When a body is deformed by the force. Some materials are more easily strained than others. |
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What is a sensor? |
A sensor is a device which detects or measures a physical property which may record, indicate or otherwise respond to it. |
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What does a sensor do? |
Detects the state of something and provides information about the state. |
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What makes a good sensor? |
Range (effective) Range (design) Repeatability Resolution Robustness/toughness Response time Accuracy Sensitivity Settling time Sensor impact Drift |
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What type of sensors are generally used by touch screens? |
Capacitance change sensor |
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What type of sensor is used to detect movement, distance and velocity? |
Ultrasonic sensors |
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What are MEMS sensors? |
Micro Electro Mechanical System sensors - used to measure changes in acceleration or angular velocity. |
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What is CEP? |
Circular Error of Probability - statistical analysis of a systems potential error |
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What is jitter? |
Jitter is the random variability of a sensor or system. It can be combated by filtering the data to smooth out the jitter. |
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What is the role of a black box? |
It takes inputs and produces outputs. We don't care how it does this. |
