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
