Electrical Engineer / Electrician Interview question

General terms used in electrical engineering

**Inrush Current**

This is the peak current that occurs when power is first applied to a unit. It is measured in peak amperes

**Power factor**

This is the relationship of the actual power usage to the apparent power usage.

For example :

Actual Power = 100 watts of power when averaged over a period of time.

Apparent Power = RMS Current X RMS Voltage.

RMS Current = 1.28 A

RMS voltage = 120Vac

Apparent Power = 1.28 A x 120 Vac

= 153.6 VA

Power Factor = 100 watts/153.6 VA

= 0.651 or 65.1%.

**True RMS current**

The acronym RMS stands for Root Mean Square. The definition of Root Mean Square is the square root of the mean square of the variable values taken throughout one cycle.

**Peak current**

This is a measurement of the normal running current, but instead of an average or RMS value, the peak value is given. This is the highest value that the current reaches during a given half cycle.

A typical load of the rectifier/capacitor-input type.

**Watts**

This is the integral of the instantaneous voltage multiplied by the instantaneous current over a half cycle.

**BTU/hr**

BTU/hr stands for British Thermal Units per hour. The British Thermal Unit is equivalent to the quantity of heat necessary to raise one pound of water one degree Fahrenheit (at 39.2°F). It provides a measurement of power converted to a form that is useful for sizing heating and cooling systems.