Electrical Theory 3 & 4
A three-resistor circuit has a total power of 25 W. Two of the resistors dissipate 10 W and 5 W respectively. How much power does the third resistor dissipate?
10 W
A parallel circuit composed of a 120 Ω and a 220 Ω resistor has a supply voltage of 240 V. What is the total circuit current?
3.091 A
A parallel circuit composed of a 10 Ω and a 22 Ω resistor. It has a supply voltage of 60 V. What is the current in the 10 Ω resistor?
6 A
Which of the following formulas is the general voltage divider formula?
Ex = (Rx/Rt) Et
In the international system of units, the prefix milli- means ________.
One thousandth
The open circuit voltage between the two terminals of a single-pole switch on a lighting circuit when the switch is in the off position is:
120 Volts
A series circuit has a total resistance of 240 Ω and a current flow of 4 A. What is the applied voltage?
240 x 4 = 960 V R x I = V
A series circuit has two resistors. The resistors dissipate 10 W and 15 W. What is the total power dissipation of the circuit?
25 W
An arc flash can produce temperatures of ____°F.
35,000
A 270 Ω, a 150 Ω, and a 220 Ω resistor are connected in parallel. The applied voltage is 480 V. What is the current total of the 270 Ω and the 150 Ω resistors?
4.98 A
A three-branch parallel circuit has resistances of 22 kΩ, 68 kΩ, and 33 kΩ connected to a 300 V source. What is the total power of the circuit?
8.14 W
A three branch parallel circuit has resistors of 27 Ω, 56 Ω, and 15 Ω. What is the total resistance?
8.23 Ω
The two resistors in a series circuit have voltages of 25 V and 60 V. The applied voltage is
85 V
A parallel circuit composed of a 150 Ω and a 270 Ω resistor has a supply voltage of 120 V. What is the current in the 150 Ω resistor?
0.8 A
A two-branch parallel circuit has a 30 Ω and a 15 Ω resistor. What is the total resistance?
10 Ω
The strength of an electromagnet is primarily proportional to its
ampere-turns
In a series circuit, the resistors have voltages dropped across them that are proportional to their resistance values. If connections are made to various points in the circuit, different voltages can be obtained. This circuit is called a(n) voltage _____.
divider
Magnetism can be explained in terms of _____ spin patterns.
electron
Magnetic lines of force are called
flux
The strength of a magnetic field is an indication of how many flux lines per square inch there are. This is called
flux density
A device that is designed to open and disconnect a circuit in the event of excessive current is a
fuse
The three substances that form natural magnets are
iron, nickel, cobalt
Lodestone is a name for a naturally occurring magnetic material that is also called
magnetite
The measure of a material's willingness to be magnetized is called
permeability
A series circuit has a total resistance of 180 Ω and an applied voltage of 120 V. What is the current flow?
E/R = I 120/180 = 0.667A
In the English system, the total force producing a magnetic field is the
magnetomotive force
An ______ magnet is a magnet that retains its magnetism without any applied power.
permanent
A method for finding total resistance of parallel resistors is
product of sum, reciprocal formula, resistors of equal value.
Of the formulas for finding the total resistance of parallel resistors, only one formula will work for any number of resistors regardless of their value. The formula is the
reciprocal
The measure of a material's resistance to being magnetized is called
reluctance
In a series circuit with two resistors, the total resistance is equal to the ______ of the two resistors.
sum
In the international system of units, the prefix kilo-means _______.
thousand
The term "load" refers to the amount of _____ in a circuit branch.
voltage
The amount of _____ across a resistor is proportional to its resistance.
voltage drop
A 62-kΩ and an 82-kΩ resistor are connected in parallel. They have a supply voltage of 480 V. What is the power of the 82-kΩ resistor?
2.81 W
A three-branch parallel circuit has a total resistance of 385.83 Ω. Two of the resistors are 680 Ω and 1500 Ω. What is the value of the third resistor?
2200 Ω
A parallel circuit is composed of two 60 Ω resistors. What is the total resistance?
30 Ω
A two-resistor series circuit has an applied voltage of 100 V. The voltage across one of the resistors is 40 V. The voltage across the other resistor is
60 V
An electrical connection made by connecting to the frame of electrical equipment is called a(n) _____ ground.
chassis
A device that is designed to open and disconnect a circuit in the event of excessive current is a
circuit breaker
In a parallel circuit, the current through each branch is inversely proportional to the resistance of the branch. Because of this, parallel circuits are sometimes called
current dividers
