3. Electrical fundamentals - Q&A

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.

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.

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

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.

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.

The output from a rotating armature AC generator would be taken from

• either the rotor or the stator.
• the rotor.
• the stator.

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.

The true power developed in this circuit is

• 20W.
• 50W.
• 12W.

A capacitor is a barrier to

• both.
• A.C.
• D.C.

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.

A 3, 5 and 2 ohms resistance is connected in series with a 10 V battery. The voltage across the 2 ohms resistor is

• 2 V.
• 10V.
• 4 V.

How many turns does the secondary winding of a 2:1 step-up transformer have?

• Less than primary.
• More than primary.
• Less turns but with thicker wire.

If the energy supplied to a circuit for 4hrs 15 minutes at 800 j/sec what would be the energy consumed?

• 3400 KW Hrs.
• 3.4 KW Hrs.
• 340 KW Hrs.

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.

If the frequency to a capacitor increases, the current through it

• decreases.
• increases.
• is zero.

If a capacitor 1 uF and an inductor 10mH are connected in parallel what is their approximate resonant frequency?

• 1.6 kHz.
• 62 Hz.
• 3.2 MHz.

What is the phase difference in a circuit with 100V, drawing 0.5 amps, consuming 50 Watts?

• 0degrees.
• 45degrees.
• 90degrees.

A generator supplies 150VAC phase and load is 10 Ohms per phase. What is the phase current ?

• 25.5 A.
• 1.5 A.
• 15 A.

Potentiometers are used as a

• variable voltage source.
• variable resistor.
• variable current source.

A 10 ohm resistor has a 14.14 V peak drop across it. What power is dissipated?

• 10 W.
• 19.99 W.
• 1.414 W.

The average value of 100 volts peak AC is

• 70.7 volts.
• 141. 4 volts.
• 63.7 volts.

In the circuit shown, if the frequency is increased from zero to resonant frequency, the circuit current would

• increase.
• decrease.
• stay the same.

In a Desynn indicator system, the rotor is

• an electromagnet.
• a permanent magnet.
• an AC magnet.

A 200 volt motor is taking 10 amperes armature current, the armature resistance is 0.1 ohm. The Back- EMF under these conditions will be

• 201 volts.
• 199 volts.
• 1 volt.

The average value of 100 volts peak AC is

• 70.7 volts.
• 141. 4 volts.
• 63.7 volts.