3. Electrical fundamentals - Q&A
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A circuit containing a resistor, capacitor and inductor where resonant frequency is met, what will the impedance of the circuit be?
- Maximum.
- Resistance across the resistor.
- Zero.
The question does not say if the LCR circuit is in series or parallel.
Series RLC at resonance: XL and XC cancel, leaving only R. Impedance = low (just R, could be very low if R is small).
Parallel RLC at resonance: XL and XC still cancel in terms of reactance, but because the components are in parallel, this results in high impedance — approaching infinite in the ideal case
Resistance is measured using what unit of temperature?
- Absolute.
- Centigrade.
- Fahrenheit.
* Absolute (Kelvin) is used in thermodynamics
* Fahrenheit is not used in electrical resistance standards
* Centigrade is the practical engineering reference point for resistance temperature coefficients
What would you use for the core in a generator current transformer?
- Air core.
- Laminated core.
- Steel Core.
A laminated core (typically made of thin, stacked sheets of grain-oriented silicon steel) is the standard and most efficient choice
The Stability windings in a 3 phase AC generator are to sense
- field oscillations.
- overvolt.
- phase shift.
he stability windings (often called damping or amortisseur windings) in a 3-phase AC generator are primarily designed to dampen mechanical rotor oscillations and stabilize the machine. They do not actively "sense" overvoltages or phase shifts; those conditions are monitored by external protection relays.
In a voltaic cell, what is the build-up on the cathode called?
- Hydration.
- Polarization.
- Sulphation.
polarization is corect
If a nicad battery is not to be used immediately it should be stored
- dry.
- fully charged.
- fully dissipated.
it should be stored fully charged
The smallest particle that a substance can be split and show the same properties as the whole is known as
- an Element.
- a Molecule.
- an Atom.
wrong answer? Molecule is the smallest while retaining properties.
Due to armature reaction in a DC motor
- the leading pole tips are magnetically weakened.
- the trailing pole tips are magnetically weakened.
- the magnetic flux is restored by moving the MNA towards the GNA.
Due to armature reaction in a DC motor ,the leading pole tips are magnetically weakened .the armature flux opposes the main field flux ate leading tip and aids it at the trailing tip :due to magnetic saturation ,the net effect is a reduction in flux at the leading tip overall demagnetization.
A battery`s internal resistance is determined by (OCV = Open Circuit Voltage, CCV = Closed Circuit Voltage)
- IR = (OCV – CCV)/ i.
- IR = (OCV + CCV) / i.
- IR = (OCV - CCV) / V.
why
Two 3 phase generators operating in parallel with different phase and line voltages will be connected in
- Parallel configuration.
- star configuration.
- delta configuration.
why?
Two 3 phase generators operating in parallel with different phase and line voltages will be connected in
- Parallel configuration.
- star configuration.
- delta configuration.
why?
Decreasing the field current in a shunt motor will
- decrease speed and increase torque.
- increase speed and increase torque.
- increase speed and decrease torque.
why
Flux losses in a transformer can be prevented by
- winding the primary on top of the secondary.
- the use of primary shielding.
- laminating the core.
How about 'laminating the core' ?
How would you find the direction of the electron flow in an armature located in a magnetic field?
- Flemings left hand rule.
- Flemings right hand rule.
- Maxwells corkscrew rule.
The question asks 'Fleming's right hand rule', because the direction of the electron is it. If the question wants 'Fleming's left hand rule' as an answer, then not 'the direction of the electron flow', but 'the direction of the motion' is suitable.
The earth lead of a 24 V equipment is 0.5 ohm resistance and carries 80 A. How much power does it dissipate?
- 1.92 kW.
- 1.152 kW.
- 3.2 kW.
Please write your question here.
In conventional current flow, what is Fleming`s right hand rule used for?
- Generators.
- Motors.
- Inductors.
Why?
A near perfect 4:1 step up transformer has it`s primary connected to 120VAC, if the secondary is connected to a load with 1600 ohms resistance, what is the current in the primary?
- 1 amp.
- 0.3 amps.
- 1.2 amps.
Why
In a Series LC circuit if the value of the capacitance is increased then the power factor will be
- greater than 1.
- less than 1.
- equal to 1.
Please write your question here.
What must you do to make a 3 F capacitor circuit into a 2 F circuit?
- Put a 2 F capacitor in parallel.
- Put a 6 F capacitor in series.
- Put a 1 F capacitor in series.
how?
If there was a mainly inductive load on an AC generator, the voltage with respect to the current would
- lag.
- be in phase.
- lead.
what you sayin bruv
The power in a circuit when voltage and resistance is given can be found by
- V*R.
- V*V*R.
- V*V / R.
Can someone do this ?
Conductance of a circuit is 2 milliMhos. What is its resistance?
- 5000 Ohms.
- 500 Ohms.
- 5 Megohms.
Can someone do this ?
A single phase circuit has an input voltage of 100V. The current is 10A and the circuit has a power factor of 0.5. The true power is
- 50W.
- 1000W.
- 500W.
Anyone can explain ?
Two 12V 40 amp hour batteries connected in parallel will produce
- 24V 80 ah.
- 12V 80 ah.
- 24V 40 ah.
Anyone can explain ?
A circuit has 115 V RMS, 2.5A at 60 degrees, what is the power dissipated?
- 79 W.
- 300 VA.
- 143 W.
Anyone can explain ?