Generation of Electricity
Production of electricity by light, heat, friction, pressure, chemical action and magnetism.
Generation of electricity, summary notes
- There are six recognised methods of producing electricity: friction, chemical action, heat, light, pressure, and magnetism.
- Chemical action produces electricity in primary and secondary cells, the aircraft battery.
- Heat applied to the junction of two dissimilar metals produces an EMF: the thermocouple, used for exhaust gas and cylinder head temperature.
- Light falling on a photocell produces an EMF; pressure applied to a crystal produces an EMF (piezoelectric effect), used in some vibration and pressure sensors.
- Magnetism, electromagnetic induction, is the primary method of generating electrical power on an aircraft.
- ⚠ Exam trap: a thermocouple converts heat to EMF; a piezoelectric crystal converts pressure to EMF. Do not confuse the two.
An engine's exhaust gas temperature indicating system uses which method of electricity generation?
Heat, a thermocouple made of two dissimilar metals (commonly chromel/alumel) produces an EMF proportional to the temperature difference between the hot and cold junctions.
Six methods concept map
Generation of Electricity
Generation of electricity quiz
Generation of Electricity, quiz
1. A thermocouple generates an EMF from:
A temperature difference between two dissimilar metal junctionsLight falling on the junction, which frees charge carriers and drives a current round the loopPressure applied across the junction, which distorts the lattice and separates the charges2. A piezoelectric device produces an EMF when it is:
Mechanically stressedHeatedIlluminated3. Of the two three-phase connections shown, in the star connection the line voltage is:
√3 times the phase voltageEqual to the phase voltageOne third of the phase voltage4. The piezoelectric effect produces an EMF from:
Pressure applied to a crystalHeat applied to a junctionLight falling on a cell5. The primary method of generating electrical power on an aircraft is:
Magnetism (electromagnetic induction)Chemical actionFriction6. How many recognised methods of producing electricity are there?
SixFourThree7. An exhaust gas temperature system typically uses which generation method?
Heat, via a thermocouplePressure, via a piezo crystalLight, via a photocell8. A photocell converts which quantity into electricity?
LightHeatPressure9. An aircraft battery generates electricity by:
Chemical actionMagnetismFriction10. Which method of generating electricity is responsible for static build-up on an airframe in flight?
FrictionChemical actionMagnetism