Mufaro's Deck

Question 1

name the main components of a dc motor

Answer 1

Stator, Commutator, brushes, rotor

Question 2

What is the main principle that DC motors use.

Answer 2

DC motors rely on a magnetic field that is created when power is supplied through the coil which is opposite to the magnet field of the stators. The commutator is responsible for switching the magnetic field of the coil so that it keeps spinning

Question 3

What is the main principle used for AC motors

Answer 3

AC motors work on Faradays law in which a change in magnetic field generates an electromotive force (EMF) in the rotor which gives rise to a current. The force acts on the motor making it rotate.

Question 4

What is the main difference between a brushed and brushless dc motor?

Answer 4

Brushed dc motors have coils through the centre that rotate around a permanent magnet while brushless dc motors have a permanent magnet in the middle that rotates around coils.

Question 5

What are the advantages of a brushless motor over a brushed?

Answer 5

Brushless motors have a better power-to-weight ratio, higher speed, instantaneous control of speed and torque, high efficiency and low maintenance.

Question 6

why are brushless motors more efficient than brushed?

Answer 6

brushed motors have friction meaning that some of the energy supplied is lost trying to overcome friction

Question 7

What is the main principle for EV motors?

Answer 7

EV motors rely on electromagnetic induction to convert electrical energy into mechanical energy

Question 8

What are the advantages of EV motors in cars?

Answer 8

no fuel required to use, environmentally friendly, better performance, lower maintenance

Question 9

what are some electrical safety equipment?

Answer 9

safety glasses, Insulated gloves, hi-vision shirt, hard hat, megger tester, safety switch, circuit breaker

Question 10

what is a megger tester?

Answer 10

A portable instrument meant to test the insulation resistance in Ohms

Question 11

how does a safety switch help?

Answer 11

When the switch detects an electrical fault such as a leakage of current it immediately turns of the electricity.

Question 12

What’s the difference between a safety switch and circuit breaker

Answer 12

Safety switch protects people from shocks
circuit breaker protects circuitry and wiring.

Question 13

What are some basic methods of testing used in the inspection of aircraft and their components?

Answer 13

Visual inspection, magnetic particle, dye penetrant, radiography, ultrasonic, eddy current.

Question 14

what tool is used in visual inspection for otherwise unreachable areas

Answer 14

fibre optic borescope

Question 15

What is Magnetic particle testing

Answer 15

An examination method for ferrous metals. A magnet is placed on the part being tested, in doing so a frpce flows from the north side of the magnet to the south through the piece, a crack lyring along the path will disrupt the magnetic flux creating a local north and south pole on both sides of the crack.

Question 16

What is dye penetrant testing?

Answer 16

Dye penetrant testing is an old method used for non-magnetic materials. It involves the wetting of a surface for examination with a dye that is either fluorescent or visible. The dye stays on the material to allow it to seep into surface discontinuities. Excess dye is then removed using a solvent before a developer is applied. The developer is used to draw out and reveal dye that is trapped in cracks, voids and flaws in the surface. the dye and the developer make the flaws in the material visible to the naked eye.

Question 17

What aircraft components can use dye penetrant or magnetic particle testing to find flaws?

Answer 17

dye penetrant and magnetic particle testing can be used to find surface flaws on components such as wheels, landing gear and braking systems.

Question 18

What is Radiographic Inspection

Answer 18

A method that involves the use of radiation projected from a source through the component to be tested and onto film. The image varies in contrast based on variations in the density and thickness of the component. the source used can either be E-rays generated from an anode or gamma rays from a radioactive isotope.

Question 19

What is ultrasonic testing

Answer 19

A portable technique used for internal flaw detection. it involves sending ultra-high frequency sound waves into a material and analysing the results. A transducer sends mechanical vibrations into a sample through a coupling medium (gel, oil or water).. An ultrasonic signal is transmitted into the component under test and a receiver picks up echoes from any opposing surfaces and any flaws. The echoes are then put through a transducer turning them into electrical signals.

Question 20

what are the pros of ultrasonic testing?

Answer 20

equipment portability, versatility as only access to one side is needed, penetrating power allows for thicker sections to be examined, highly sensitive and accurate in the measurement of small flaws.

Question 21

What are the disadvantages of ultrasonic testing?

Answer 21

can be affected by metal grain size or second phases such as graphite, signal transmission into other components such as bearings can complicate interpretation, problems when multiple defects occur close to each other or near the surface

Question 22

What are eddy current techniques?

Answer 22

an inspection process for detection of subsurface cracks and/or corrosion. It involves inducing small electrical currents a conductive material with a probe and observing the interaction.

Question 23

which aircraft component is the eddy current technique primarily used on?

Answer 23

The eddy current technique is primarily used on airframes of aircraft