3. Electrical fundamentals - Q&A
156 questions found
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The time required to fully charge a 1 u(micro)F capacitor in series with a 100k ohm resistor is
- 100 seconds.
- 100 milliseconds.
- 500 milliseconds.
the ans should be 100 millisec. T=RC.
Which of the following would be used to calculate transformer turns ratio?
- Secondary turns / primary turns.
- Primary turns * secondary turns.
- Primary turns / secondary turns.
transformer ratio and turn ratio are reciprocal...???
A sine wave of RMS value 7.07 volts has a peak to peak value of
- 20 volts.
- 10 volts.
- 0.707 volts.
if anyone could guide...
A 20 Picofarad capacitor with a 1 Megohm resistor takes how long to charge?
- 100 microseconds.
- 20 milliseconds.
- 1 second.
pls solve
What is the mutual inductance if two coils of 10mH and 500mH have 90% of the flux transferred from one to the other?
- 459mH.
- 5mH.
- 63mH.
pls solve it for me
In a an DC motor, the rotation of the MNA
- is opposite to the rotation of the armature.
- is slightly less speed than the rotation of the armature.
- is the same as the rotation of the armature.
Wouldn't the rotation of MNA be in the same direction as rotation of armature?
The secondary coil of a transformer has 1500 turns and 10Ohm resistance. The primary coil has 1kOhm resistance. How many turns does the primary coil have?
- 15,000.
- 1,500,000.
- 150,000
How does the answer comes to 15000?
A potentiometer varies
- resistance.
- current.
- voltage.
potentiometer varies resistance, your answer is voltage
What is the reflected impedance in the primary of the transformer circuit shown?
- 20 ohms
- 500 ohms
- 50 ohms
? should be 50 ohms !
Armature reaction in a DC generator causes
- MNA to move in the opposite direction of rotation.
- MNA to move in the direction of rotation.
- GNA to move in the direction of rotation.
Another question says MNA rotates opposite armature rotation, which is true then? thx for your help.
In a an DC motor, the rotation of the MNA
- is opposite to the rotation of the armature.
- is slightly less speed than the rotation of the armature.
- is the same as the rotation of the armature.
MNA rotates in the same direction than the armature, right?
Which of the following would be used to calculate transformer turns ratio?
- Secondary turns / primary turns.
- Primary turns * secondary turns.
- Primary turns / secondary turns.
isn't this wrong?
In a 4:1 step up transformer, what would give a reflected impedance of 1 kOhm?
- 1 kOhm.
- 16 kOhm.
- 4 kOhm.
why??
Potentiometers are used as a
- variable voltage source.
- variable resistor.
- variable current source.
Potentiometers are used as voltage dividers are the not? they have 3 connections, surely a rheostat would be a better variable resistor?
The 5th coloured band on a resistor represents the
- reliability or temperature coefficient.
- tolerance.
- multiplier.
Isn't it the tolerance in coloured band is represent in the 4th band?
Potentiometers are used as a
- variable voltage source.
- variable resistor.
- variable current source.
Isn't it potentiometer relates to variable voltage source?
What happens to the current in a series resistive resonant circuit?
- It is maximum.
- It is minimum.
- It is zero.
Isn't it that at resonant, we have high impedance hence we should have minimum current flow?
How many amperes will a 28-volt generator be required to supply to a circuit containing five lamps in parallel, three of which have a resistance of 6 ohms each and two of which have a resistance of 5 ohms each?
- 1 ampere.
- 25.23 amperes.
- 1.11 amperes.
resistance, then use ohms law (I=V/R) to find the total current. It is a tricky calculation to do without a calculator, so round the total resistance up (to 1 ohms) then choose the nearest answer for I.
What is the current in the circuit with a resistance of 8 ohms, inductive reactance of 12 ohms, capacitive reactance of 18 ohms with 20 volts applied across it?
- 10 amps.
- 1 amp.
- 2 amps.
Can anyone explain me this one...?
The 5th coloured band on a resistor represents the
- reliability or temperature coefficient.
- tolerance.
- multiplier.
then what is 4th colored band for????
In the circuit shown, the power developed across the 10 kilo ohm resistor is
- 250 mW.
- 250 W.
- 50 mW.
Please Explain 250mW as answer
A transformer has 1200 turns primary and 4800 turns secondary. What value of load resistance would be required to give a reflected impedance of 1000 ohms?
- 4 kOhm.
- 1 kOhm.
- 16 kOhm.
How to do it?
The circuit shown is at resonance. If the value of the inductance is trebled, the impedance will
- stay the same.
- treble.
- reduce by one-third.
parallel circuit dynamic impedance Z=L/CR. so inductance trebled impedance also treble.
is it correct ?
A paramagnetic material has a relative permeability of
- zero.
- less than unity.
- greater than unity.
why?
Reactive sparking is reduced by
- interpoles.
- compensating windings.
- auxiliary windings.
why interpoles?