2365 612 electrical sciences with correct answers 2025
Power generated at - correct answer25kv
Power transmitted at - correct answerStepped up from 25kv into 275/400kv and 132kv
Power distributed at - correct answer33/11kV and 230/400v
How are transformers kept cool - correct answerAir, oil or gas
MCB type B, C, D - correct answerBSEN 60898
RCD - correct answerBSEN 61008
Power factor - correct answerThe ratio of true power to apparent power. A better factor means
current use age is reduced so a smaller cable size can be used and lower demand needed
Pf - correct answerTrue power (kW) % Apparent power (kVA)
How to create a leading power factor - correct answerTo correct a lagging power factor we can
use a capacitor (bulk and load connection) or a synchronous motor
Inductance - correct answerhow easily a certain material will induce an electromotive force
(emf) within a circuit.
AC makes it flux any times a second so producing inductive reactance
Inductive Reactance (Xl) - correct answerThe opposition to current of AC caused by inductance
of a circuit, expressed in ohms. 2pieFL
, Pie=3.14 f=frequency l=inductance
Impedance z - correct answerZ = square root of Rsquared + XLsquared
Capictors - correct answerCharge like batteries in AC so produces opposition to current called
capacitive reactance (XC)
Capacitive reactance XC - correct answer1% 2pieFC
Pie=3.14 F is frequency C is capacitance
Total reactance - correct answerXL -XC or XC - XL
XC capacitive reactance
XL inductive reactance
Impedance (z) - correct answerZ= square root of rsquared+xsqaufed
Impedance the opposition to current in AC comprising of resistance, inductive and capacitive
reactance.
DC machine basics - correct answerField winding generates the static magnetic field. Armature
winding which via the commutator created a changing magnetic field.
Change direction in a series motor - correct answerWe reverse the polarity of field or armature.
Same with a shunt motor.
Discharge lighting eg low pressure mercury - correct answergenerates light through electrical
discharge through ionised gas in luminaire. Noble gas ignites it. Phosphor coating makes it
visible for us to see.
Transformer losses - correct answerCopper loss-created by current through cables.
Iron losses-magnetic losses in core of transformer called eddy currents or hysteresis losses.
Power generated at - correct answer25kv
Power transmitted at - correct answerStepped up from 25kv into 275/400kv and 132kv
Power distributed at - correct answer33/11kV and 230/400v
How are transformers kept cool - correct answerAir, oil or gas
MCB type B, C, D - correct answerBSEN 60898
RCD - correct answerBSEN 61008
Power factor - correct answerThe ratio of true power to apparent power. A better factor means
current use age is reduced so a smaller cable size can be used and lower demand needed
Pf - correct answerTrue power (kW) % Apparent power (kVA)
How to create a leading power factor - correct answerTo correct a lagging power factor we can
use a capacitor (bulk and load connection) or a synchronous motor
Inductance - correct answerhow easily a certain material will induce an electromotive force
(emf) within a circuit.
AC makes it flux any times a second so producing inductive reactance
Inductive Reactance (Xl) - correct answerThe opposition to current of AC caused by inductance
of a circuit, expressed in ohms. 2pieFL
, Pie=3.14 f=frequency l=inductance
Impedance z - correct answerZ = square root of Rsquared + XLsquared
Capictors - correct answerCharge like batteries in AC so produces opposition to current called
capacitive reactance (XC)
Capacitive reactance XC - correct answer1% 2pieFC
Pie=3.14 F is frequency C is capacitance
Total reactance - correct answerXL -XC or XC - XL
XC capacitive reactance
XL inductive reactance
Impedance (z) - correct answerZ= square root of rsquared+xsqaufed
Impedance the opposition to current in AC comprising of resistance, inductive and capacitive
reactance.
DC machine basics - correct answerField winding generates the static magnetic field. Armature
winding which via the commutator created a changing magnetic field.
Change direction in a series motor - correct answerWe reverse the polarity of field or armature.
Same with a shunt motor.
Discharge lighting eg low pressure mercury - correct answergenerates light through electrical
discharge through ionised gas in luminaire. Noble gas ignites it. Phosphor coating makes it
visible for us to see.
Transformer losses - correct answerCopper loss-created by current through cables.
Iron losses-magnetic losses in core of transformer called eddy currents or hysteresis losses.
