POE Flashcards
Describe electrical charges within atoms?
Nucleus - Protons and neutrons
Valence shell - Electrons
Protons - Positive charge
Neutrons - Neutral / zero charge
Electrons - Negative charge
Describe electrical state of atoms?
More protons than electrons - Positive ion
More electrons than protons - Negative ion
Equal protons and electrons - Neutral ion
Describe the conductive properties of matter?
Conductor - Loosely bonded
Semi conductor - In between - neither loose or tight bond
Insulator - Tightly bonded
Describe the production of electro-motive force?
EMF
- Generation of force to separate positive and negative charges to create a difference in charge between 2 terminals
- This difference is known as EMF
- Potential difference or voltage and is measured in volts
Describe factors affecting the production of EMF?
Heat - Based off the material
Chemical - Resistance (length, resistivity and cross sectional area)
Magnetism - Strength of magnetic field, active length of conductor, velocity at which the conductor cuts through the field and the angle (V=BLvSin(angle))
Describe characteristics of a cell?
Primary cell - Cannot be charged
Secondary cell - Can be recharged
Describe operations of a cell?
- The build up of electrons on the negative terminal
- 2 dissimilar metals in an electrolyte solution
- Copper is ready to give away electrons and the zinc is ready to take more electrons
Describe the aircraft uses of a different forms of EMF generation?
Chemical - APU, emergency power, start engine
Magnetism - High power generator, small power tach generator
Heat - Thermocouples used for engine intake temperature, exhaust temperature and engine cylinder - head temperature
Relationship between voltage, current and resistance?
Voltage increases = Current increases
Resistance increases = current decreases
Describe factors affecting resistance?
R = pL / A
Job is to resist current flow
Describe factors affecting current?
Rate of electrons flowing through circuit - resistance affects it
