3. Electrical fundamentals - Q&A
168 questions found
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To supply a 24volt output with a transformer with a 5:1 turns ratio, the input required is
- 4.8
- 24V.
- 120V.
help me pls
Total resistance in a parallel resistor circuit, of R1 and R2 is
- RT = 1/R1 + 1/R2.
- 1/RT = (R1 * R2) ÷ (R1 + R2).
- 1/RT = 1/R1 + 1/R2.
i think the answer here is wrong! the true answer is RT = (R1 x R2) ÷ (R1 + R2)
A 50 microFarad capacitor is fed with a current of 25 milliAmpere. How long will it take to charge it to 100Volts?
- 1 second.
- 0.2 seconds.
- 12 minutes.
How to find it?
The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking
- the voltage with rated load switched ON.
- the voltage on open circuit.
- the voltage off load.
What is the difference between Off load and open circuit?
In a resonant parallel circuit, current is
- zero.
- minimum.
- maximum.
Please can anyone explain
In what equipment is a photon radiated when an electron leaves a hole?
- Photo-cell.
- LED.
- Photo diode.
Please explain
What polarity do interpoles take in a DC generator?
- The same as the next main pole behind in the direction of rotation.
- Either, providing they lay on M.N.A.
- The same as the next main pole ahead in the direction of rotation.
Help!? I thought Interpoles in a generator are same polarity as main pole ahead of it? Behind for motors?
A transformer has 2000V, 500 turns on the primary and 50 turns on the secondary. What would be the line voltage if the transformer were Delta/Star connected?
- 200V.
- 450V.
- 346V.
A transformer has 2000V , 500 turns on the primary and 50 turns on the secondary . what would be the line voltage if the transformer were delta/star connected?
A 48-volt direct current source is required to furnish 192 watts to a parallel circuit consisting of three resistors of equal value. What is the value of each resistor?
- 4 ohm.
- 36 ohm.
- 12 ohm.
How do you work this out?
An autotransformer is
- primary and secondary coils.
- primary coil only.
- primary and secondary coils on single bar.
Why
A transformer should always have its
- primary shorted or off load.
- secondary shorted or on load.
- secondary open circuit or on load.
Shouldn't it be secondary shorted or on load?
An increase in operating temperature in most electrical devices carrying current results in
- a decrease in resistance and an increase in current.
- no effect on the resistance and current.
- an increase in resistance and a decrease in current.
isnt R inversly proprtion to Temp? Help
The poles of a DC generator are laminated to
- reduce eddy current losses.
- reduce flux losses.
- reduce hysteresis losses.
isnt it eddy current?? Help
What polarity do interpoles take in a DC motor?
- Either, provided they lay on the MNA.
- The same as the next main pole ahead in the direction of rotation.
- The same as the next main pole behind in the direction of rotation.
Can someone explain this?
A 10:1 step up power transformer has 120 V, and 3A flowing through the primary, and 0.285 A flowing through the secondary what is the efficiency?
- 90%.
- 95%.
- 85%.
can somebody pls explain that with a formula
A conductor with a positive Q (charge) of 4C has 12.56 x 1018 electrons added to it. It will have a Q =
- 6.
- 2.
- 0.
help?
If a capacitor 1uF and an inductor 10mH are connected in parallel what is their approximate resonant frequency?
- 1.6 kHz.
- 62 Hz.
- 3.2 MHz.
help?
Three inductors 10 mH, 5 mH and 20 mH are connected in parallel. What is the total inductance?
- Without knowing the coupling factor the total inductance cannot be found.
- 2.86mH.
- 1.35mH.
help?
In a 4:1 step-up transformer, 120V is applied to the primary, and the load on the secondary is 1600 Ohms. What is the current in the primary?
- 0.075A
- 1.2A
- 3A
help?
A 24V battery has an internal resistance of 1 ohm. When connected to a load, 12 amps flows. The value of the load is
- 12 ohms.
- 1/2 ohm.
- 1 ohm.
help?
The mark-to-space ratio of the waveform shown is
- A to D / D to E.
- D to E / D to C.
- A to B / B to C.
Please explain this one, I don't understand, thank you.
A circuit has a resistance of 50 ohms and an inductance of 0.2 Henry. If it is connected to a 200 volt 50 Hz supply the reactance will be
- 31.42 ohms.
- 62.84 ohms.
- 6.284 ohms.
help ?
A capacitor is a barrier to
- both.
- A.C.
- D.C.
help plz sos ;)
An inductor of resistance 5 kO and inductance 2mH is connected to a DC circuit. The time constant is
- 400 ns.
- 10 seconds.
- 40 ms.
can anyone please explain? thanks
If the resistance of a resistor which is in series with two other resistors is doubled
- the current in that resistance is doubled.
- the volts drop across that resistor increases.
- the current in that resistance is halved.
why cant it be current halved?