Electrical Theory Unit 8

The output power of a transformer is 100W and the transformer efficiency is 90 percent. What is the transformer input if the output is lower than the input? Formula: Input = Output/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?

32

The maximum continuous load on an overcurrent protection device is limited to 80 percent of the device rating. If the overcurrent device is rated 100A, the maximum continuous load is _____.

80A

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

0.20

The decimal equivalent for "75 percent" 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 if they carry 16A and the 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 percent" is _____.

2.25

The total value of 2, 7, 8, and 9 is approximately _____.

25

The decimal equivalent for "300 percent" is _____.

3

What is the area in sq in. of a trade size 2 raceway? Formula: Area = Pi x r2, Pi = 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 a 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: Power = 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

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

False

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

Multiplier

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