Basic Electrical Theory: Unit 8 - Math

The output power of a transformer is 100W and the transformer efficiency is 90%. What is the transformer input if the output is lower that the input? Formula: Input/Efficiency

110W

The numeric equivalent of 12² is ___________.

144

The numeric equivalent of 4² is ___________.

16

What is the volume (in cubic inches) of a 4 x 4 x 1.50 in. box?

24 cu. in.

What is the approximate square root of 1,000 (Ö1,000)?

32

The feeder calculated load for an 8 kW load, increased by 20 percent is _____.

9.60 kW

Squaring a number means multiplying the number by itself.

True

What is the kW of a 75W load?

0.075 kW

The decimal equivalent for the fraction "4/18" is _____.

0.20

The decimal equivalent for the fraction "1/2" is ________.

0.50

The decimal equivalent for "75%" is __________.

0.75

What is the reciprocal of 1.25?

0.80

The square root of 3 (√3) is ___.

1.732

What is the maximum distance that two 14 AWG conductors can be run is that carry 16A and maximum allowable voltage drop is 10V? D = (Cmil x VD)/(2 x K x I) D = (4,110 cmil x 10V)/(2 x 12.90 ohms x 16A)

100 ft

The decimal equivalent for "225%" is ___________.

2.25

An overcurrent protection device (breaker fuse) must be sized no less than 125% of the continuous load. If the load is 16A, the overcurrent protection device will have to be sized at no less than _____________.

20A

The approximate sum of 2, 7, 8 and 9 is equal to _____.

25

The decimal equivalent for "300%" is ___________.

3

What is the area in sq. in. of a trade in size 2 raceway? Formula : Area = π x r², π = 3.14, r = radius (1/2 of the diameter)

3 sq. in.

What is the current in amperes of an 18kW, 208V, three-phase load? Current: I = VA/( E x √3) Current: I = 18.000W/(208V x 1.732)

50A

What is the power consumed in watts by 12 AWG conductor that is 100 ft long and has a resistance (R) of 0.20 ohms, when the current (I) in the circuit is 16A? Formula: I² x R

50W

A continuous load requires an overcurrent protection device sized no smaller than 125 percent of the load. What is the maximum continuous load permitted on a 100A overcurrent protection device?

80A

The maximum continuous load of an overcurrent protection device is limited to 80% of the device ration. If the overcurrent device is rated at 100A, the maximum continuous load is ____________.

80A

Deriving the square root of a number is almost the same as squaring a number.

False

The volume of an enclosure is expressed in _____, and it is calculated by multiplying the length, by the width, by the depth of the enclosure.

cubic inches

To change a percent value to a decimal or whole number, drop the percentage sign and move the decimal point two places to the _________.

left

The method of increasing a number by another number is done by using a _____________.

multiplier