3. Electrical fundamentals - Q&A

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.

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.

Resistance is measured using what unit of temperature?

• Absolute.
• Centigrade.
• Fahrenheit.

What would you use for the core in a generator current transformer?

• Air core.
• Laminated core.
• Steel Core.

The Stability windings in a 3 phase AC generator are to sense

• field oscillations.
• overvolt.
• phase shift.

In a voltaic cell, what is the build-up on the cathode called?

• Hydration.
• Polarization.
• Sulphation.

If a nicad battery is not to be used immediately it should be stored

• dry.
• fully charged.
• fully dissipated.

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.

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.

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.

A small air gap between magnetic poles results

• in a weaker field than a large air gap, for the same magnetising force.
• in a stronger field than a large air gap, for the same magnetising force.
• in the same field as a large air gap, for the same magnetising force.

What is the combined value of resistances of 4 ohm and 6 ohm connected in parallel?

• 0.24 ohm.
• 2.4 ohm.
• 24 ohm.

What is the power dissipated in a 500 ohm resistor with a 3A flow?

• 4.5 kW.
• 1.5 kW.
• 750 kW.

A DC generator armature has 6 poles and is lap wound. The number of brushes required are

• 2.
• 3.
• 6.

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.

A 3 phase generator whose phase and line voltages are different is connected in

• Parallel configuration.
• star configuration.
• delta configuration.

The power in a circuit when voltage and resistance is given can be found by

• V*R.
• V*V*R.
• V*V / R.

Decreasing the field current in a shunt motor will

• decrease speed and increase torque.
• increase speed and increase torque.
• increase speed and decrease torque.

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.

Conductance of a circuit is 2 milliMhos. What is its resistance?

• 5000 Ohms.
• 500 Ohms.
• 5 Megohms.

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.

The line voltage of a 3 phase star connected AC generator is

• equal to the phase voltage.
• greater than the phase voltage.
• less than the phase voltage.

In conventional current flow, what is Fleming`s right hand rule used for?

• Generators.
• Motors.
• Inductors.

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.

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.