electrical fundamentals quiz Flashcards
what is the name of an electrically neutral group of two or more atoms held together by chemical bonds
molecule
what is correct about electrical current in a conductor?
when an electron enters a conductor, another electron at the opposite end is pushed out
how is voltmeter connected
in parallel with the terminal of a power source and/or a load
when electrons move through a conductor. the acceleration lost is turned into which kind of energy?
Thermal energy
what does the movement of electrons depends on?
conductor material, conductor cross-sectional, potential difference and temperature
where on the aircraft is the electrical field more concentrated
on the trailing edge of the wings, elevators and fins
faraday law
when an armature rotates between the magnet’s poles upon an axis perpendicular to the magnetic field, the flux linkages of the armature changes continuously, due to this, an EMF is induced in the armature
what is true about voltage generated by friction
they can reach very high values of unto thousands of volts.
what happens if a conductor moves through a magnetic filed, and that motion is in some part at right angles to the direction of the field?
an electromotive force (EMF) is induced across the conductor.
what happens when there is a current flowing through a voltage generator operating on-load?
the terminal voltage decreases as the current increases.
what is the fundamental difference between primary cells and secondary cells?
primary cells are non-rechargeable, secondary cells are rechargeable
what does it mean when a battery has a capacity of 50Ah?
it supplies a current of 5A for 10 hours
what can Ohm’s law be used for?
to calculate an unknown value for either voltage, current or resistance
which law describes the relationship between current and voltage for most conductors?
Ohm’s law
in a Wheatstone bridge, what is used to indicate potential difference?
a Galvanometer
what is power?
power is the rate at which either work is done or heat is transferred. it is measured in joules per second (j/s), which is also known as watts (W)
why should permanent magnets be kept away from external magnetic fields?
to prevent the magnet from becoming de-magnatised
what are capacitors capable of doing in a circuit for a short time?
storing charge.
what happens when the lines of magnetic flux come closer together?
the magnetic field becomes stronger and there flux density increase.
what can be integrated parallel to a coil as a precaution to lower the back electromotive force (EMF)?
freewheeling diodes
the action of moving a coil, or loop of wire, through a magnetic field induces a voltage in the coil with a magnitude that is proportional to…
the speed or velocity of the movement
how can the rated power output be calculated?
by multiplying a motors rates torque by the rotational speed.
two different voltages can be measured in aircraft three-phase systems: one phase referenced to the ground and one measured phase-to-phase. what are the respective voltages?
ground 115v phase to phase: 200v
what is the name of the product of the root means square (RMS) values of voltage across the resistance and the current flowing through it?
the true power of the resistance.
with what type of connection can a standard three-phaser system be obtained?
Star or Y connection
some types of alternating current (AC) are classified according to the shape of the waveform. what does a triangular wave indicate?
a steady rate of change of voltage over each half cycle
under what circumstances does the capacitive reactance of a capacitor decrease?
as a capacitance increases, and as the frequency increases.
what is the difference between an electrical current through a solid material, and a current through a liquid (electrolyte)?
in the solid, the electrons carry the charge; in the liquid, the ions carry the charge.
what is the purpose of a step up transformer and step down transformer?
a step-up transformer increases the voltage and decreases the current; a step-down transformer decreases the voltage and increase the current.
name 2 electronic filters
High-pass filter (HPF)
Low-pass filter (LPF)
Which type of circuit is used in most aircraft generators?
A three-phase or polyphase circuit.
what does am alternating current (AC) square waveform represent?
it is mostly used for representing electrical signals, e.g., voltage circuit outputs and clock signals
what is the difference between induction motors and direct current (DC) motors?
changes in load do not affect their speed much but change their torque.
which alternation current (AC) motor is typically used as a generator
Synchronous
