Basic Electrical Principles Flashcards

What is the effect of increasing temperature on the resistance of most metallic conductors?

Answer: Resistance increases

In most metals, higher temperatures cause increased atomic vibration, which impedes electron flow and raises resistance.

In a parallel circuit with two branches carrying 4A and 6A respectively, what is the total current from the source?

Answer: 10 A

In a parallel circuit, total current equals the sum of branch currents: 4 + 6 = 10 A.

What is 'apparent power' in an AC circuit measured in?

Answer: Volt-amperes (VA)

Apparent power is the product of RMS voltage and RMS current in an AC circuit, expressed in volt-amperes (VA).

Which type of motor is most commonly used in elevator traction drives?

Answer: AC induction motor

AC induction motors are widely used in elevator traction drives due to their reliability, low maintenance, and efficiency with variable frequency drives.

What does a voltmeter measure and how should it be connected in a circuit?

Answer: Voltage; connected in parallel

A voltmeter measures the potential difference (voltage) between two points and must be connected in parallel across those points.

What is the purpose of a contactor in elevator electrical systems?

Answer: To switch high-current motor circuits using a low-current control signal

A contactor is an electrically operated switch that uses a small control current to open or close a high-current circuit, such as a motor power circuit.

What is the correct color code for the ground wire in US electrical installations?

Answer: Green or bare copper

In US wiring, the equipment grounding conductor is identified by green insulation, green with a yellow stripe, or bare copper.