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From Wikipedia
OhmThe ohm (symbol: Î©) is the SI unit of electrical resistance, named after Georg Simon Ohm.
Definition
The ohm is defined as a resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.
\Omega = \dfrac{\mbox{V}}{\mbox{A}} = \dfrac{\mbox{m}^2 \cdot \mbox{kg}}{\mbox{s} \cdot \mbox{C}^2} = \dfrac{\mbox{J}}{\mbox{s} \cdot \mbox{A}^2}=\dfrac{\mbox{kg}\cdot\mbox{m}^2}{\mbox{s}^3 \cdot \mbox{A}^2}= \dfrac{\mbox{J} \cdot \mbox{s}}{\mbox{C}^2}
In many cases the resistance of a conductor in ohms is approximately constant within a certain range of voltages, temperatures, and other parameters; one speaks of linearresistors. In other cases resistance varies (e.g., thermistors).
Commonly used multiples and submultiples in electrical and electronic usage are the milliohm, ohm, kilohm, and megohm.
In alternating current circuits, electrical impedance is also measured in ohms.
Conversions
The SI unit of electrical conductance is the siemens, also known as the mho (ohm spelled backwards, symbol is â„§); it is the reciprocal of resistance in ohms.
Power as a function of resistance
The power dissipated by a linear resistor may be calculated from its resistance, and voltage or current. The formula is a combination of Ohm's law and Joule's laws:
- P=V\cdot I =\frac{V^2}{R} = I^2\cdot R
where P is the power in watts, R the resistance in ohms, V the voltage across the resistor, and I the current through it.
This formula is applicable to devices whose resistance varies with current.
Use of the Î© symbol in electronic documents
Care should be taken when preparing documents (including HTML documents) which make use of the symbol Î©. Some document editing software will attempt to use the symboltypeface to render the character. Where the font is not supported, a W is displayed instead (a "10 W" resistor instead of a "10 Î©" resistor, for instance). As this represents the SI unit of power, not resistance, this can lead to confusion.
Unicode encodes an ohm symbol (U+2126, Ω) distinct from Greek omega among letterlike symbols, but it is only included for backwards compatibility and the Greek uppercase omega character (U+03A9, Ω) is preferred.
Ohm's lawOhm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them. The mathematical equation that describes this relationship is:
From Encyclopedia
Ohm's lawOhm's law [for G. S. Ohm ], law stating that the electric current i flowing through a given resistance r is equal to the applied voltage v divided by the resistance, or i = v / r. For general application to alternating-current circuits where inductances and capacitances as well as resistances may be present, the law must be amended to i = v / z, where z is impedance . There are conductors in which the current that flows is not proportional to the applied voltage. These do not follow this law and are called nonohmic conductors.
From Yahoo Answers
Question:what is ohms law and how is power determined?
how is electrical power related to mechanical and thermal energy?
what parameters and formula determine the resistance of a material?
kirchhoff's loop rule for circuit analysis is an expression of conservation of ___________
Answers:This will help:
Question:Please help me with this. I am really struggling with it... Thanks in advance :)
Here are the questions...
1. What is the total resistance in a circuit that contains three 60 resistors connected in series?
A. 20
B. 60
C. 120
D. 180
2. What type of circuit measurement is made by placing a meter's test leads in parallel with a deenergized component?
A. Current
B. Resistance
C. Voltage
D. Power
3. What is the total current of the circuit shown in the figure below?
A. 10 A
B. 3 A
C. 1 A
D. 0.1 A
4. A series circuit contains four resistors. In the circuit, R1 is 80 , R2 is 60 , R3 is 90 , and R4 is 100 . What is the total resistance?
A. 70.3
B. 250
C. 330
D. 460
5. What is the voltage at points B and D in the figure shown below?
A. 4 V
B. 6 V
C. 8 V
D. 10 V
6. Which one of the following is the correct power formula?
A. P = IR
B. P = E/R
C. P = EI
D. P = I2/R
7. What is the total resistance of a circuit that contains two 100 resistors connected in parallel?
A. 10
B. 30
C. 50
D. 150
8. Which of the following is the correct Ohm's law formula used to find current?
A. I = R/E
B. I = E/R
C. I = E2/R
D. I = PR
9. The figure below shows a DC motor that contains a series field winding (F1) with a resistance of 10 , a parallel field winding (F2) with a resistance of 20 , and an armature with a resistance of 2 . What is the total resistance of this motor?
A. 11.82
B. 16.4
C. 24
D. 32
10. If the voltage in a circuit is 24 V and the current is 2 A, what is the total power in the circuit?
A. 6 W
B. 48 W
C. 72 W
D. 102 W
11. What does the abbreviation VOM stand for?
A. volt-ohm-megohm
B. volt-ohm-milliammeter
C. volume-ohm-microamp
D. volume-origin-megohm
12. What is the voltage drop across R4 in the diagram shown below?
A. 10 V
B. 30 V
C. 70 V
D. 80 V
13. Which of the following is the correct Ohm's law formula used to find resistance?
A. R = EI
B. R = E/I
C. R = PI
D. R = I/E
14. What is the total power in a circuit with a current of 4 A and a resistance of 12 ?
A. 4 W
B. 16 W
C. 48 W
D. 192 W
15. A circuit contains four resistors connected in series. R1 is 100 , R2 is 200 , R3 is 240 , and R4 is 600 . What is the total circuit resistance?
A. 1,200
B. 1,140
C. 600
D. 80
16. What is the power dissipated by the parallel resistor circuit shown below?
A. 10 W
B. 48 W
C. 60 W
D. 100 W
17. What is the power dissipated by R2 in the circuit shown in the figure in Question 16?
A. 5 W
B. 12 W
C. 16 W
D. 33.3 W
18. Which one of the following voltages should never be measured directly with a VOM?
A. 100 V
B. 500 V
C. 800 V
D. 1,200 V
19. Which of the following is the correct formula for finding power in a DC circuit?
A. P = IR
B. P = I2R
C. P = ER
D. P = E2I
20. What is the voltage in a circuit with a resistance of 100 and a current of 0.04 A?
A. 4 V
B. 8 V
C. 10 V
D. 40 V
21. The pointer of an analog meter is connected to a
A. permanent magnet.
B. electromagnet.
C. coil suspended by bearings.
D. voltage to frequency converter circuit.
22. What is the resistance in a circuit that has a voltage of 60 V and a current of 2 A?
A. 10
B. 30
C. 60
D. 120
23. What is the power dissipated by a resistor with a current of 0.02 A and a resistance of 1,000 ?
A. 0.4 W
B. 4 W
C. 20 W
D. 200 W
24. In a circuit, two resistors of 100 and 80 are connected in parallel. The parallel group is then connected in series with a 100 resistor. What is the total resistance of the circuit?
A. 280
B. 144
C. 120
D. 44
25. What is the power of a parallel circuit with a resistance of 1,000 and a current of 0.03 A?
A. 0.09 W
B. 0.9 W
C. 9 W
D. 30 W
Answers:too many!
I'll try a few
PS, these are all very very simple. If you have any plans to continue in a technical education, you have to be able to do these.
1. What is the total resistance in a circuit that contains three 60 resistors connected in series?
D. 180
2. What type of circuit measurement is made by placing a meter's test leads in parallel with a deenergized component?
B. Resistance
4. A series circuit contains four resistors. In the circuit, R1 is 80 , R2 is 60 , R3 is 90 , and R4 is 100 . What is the total resistance?
C. 330
6. Which one of the following is the correct power formula?
C. P = EI
7. What is the total resistance of a circuit that contains two 100 resistors connected in parallel?
C. 50
8. Which of the following is the correct Ohm's law formula used to find current?
B. I = E/R
10. If the voltage in a circuit is 24 V and the current is 2 A, what is the total power in the circuit?
B. 48 W
11. What does the abbreviation VOM stand for?
none. It is volt ohm meter
13. Which of the following is the correct Ohm's law formula used to find resistance?
A. R = EI
14. What is the total power in a circuit with a current of 4 A and a resistance of 12 ?
D. 192 W
15. A circuit contains four resistors connected in series. R1 is 100 , R2 is 200 , R3 is 240 , and R4 is 600 . What is the total circuit resistance?
B. 1,140
18. Which one of the following voltages should never be measured directly with a VOM?
D. 1,200 V
19. Which of the following is the correct formula for finding power in a DC circuit?
B. P = I2R if that is P = I R
20. What is the voltage in a circuit with a resistance of 100 and a current of 0.04 A?
A. 4 V
.
Question:1. Which one of the following voltages should never be measured directly with a VOM?
A. 100 V
B. 500 V
C. 800 V
D. 1,200 V
2. Which of the following is the correct formula for finding power in a DC circuit?
A. P = IR
B. P = I2R
C. P = ER
D. P = E2I
3. What is the voltage in a circuit with a resistance of 100 W and a current of 0.04 A?
A. 4 V
B. 8 V
C. 10 V
D. 40 V
4. The pointer of an analog meter is connected to a
A. permanent magnet.
B. electromagnet.
C. coil suspended by bearings.
D. voltage to frequency converter circuit.
5. What is the resistance in a circuit that has a voltage of 60 V and a current of 2 A?
A. 10 W
B. 30 W
C. 60 W
D. 120 W
6. What is the power dissipated by a resistor with a current of 0.02 A and a resistance of 1,000 W?
A. 0.4 W
B. 4 W
C. 20 W
D. 200 W 7. In a circuit, two resistors of 100 W and 80 W are connected in parallel. The parallel group is then connected in series with a 100 W resistor. What is the total resistance of the circuit?
A. 280 W
B. 144 W
C. 120 W
D. 44 W
8. What is the power of a parallel circuit with a resistance of 1,000 W and a current of 0.03 A?
A. 0.09 W
B. 0.9 W
C. 9 W
D. 30 W
Answers:When you copy and paste these, why don't you convert the "W"s into "ohms"?
Hey! The guy who did your homework for you ("The Great One") gave three WRONG answers (as of 1930 MST 11-14. He'll probably redo it after he reads this)...heh, heh, heh...
Question:A "gauge 8" jumper cable has a diameter d of 0.326 centimeters. The cable carries a current I of 30.0 amperes. The electric field E in the cable is 0.062 newtons per coulomb.
What electric field would have been required to create a current of 30.0 amperes in a copper "gauge 10" wire with diameter equal to 0.259 centimeters?
Express your answer in N/C. Use three significant figures.
Answers:We work on car problems here not home work problems. I did mine when I was in school and so should you. That's called "learning".
From Youtube
Ohm's Law :review of electrical math Ohm's Law
Ohm's Law for Circuit Section :Ohm's Law for Circuit SectionThe Ohm's law is the physical law determining the relationship between the voltage, the current power and the resistance of the conductor within the electric circuit. It is named after the discoverer - Georg Ohm, who experimentally proved, that the I current power, flowing along the uniform metal conductor, not affected by external forces, is proportionate to U voltage on the ends of the conductors. There are several formulations of the Ohm's law. If during the flow of current the voltage and the properties of the conductor remain unchanged, the current power in the conductor is directly proportionate to the voltage between the ends of the conductor and inversely proportionate to the resistance of the conductor. The current power on the uniform circuit section is directly proportionate to the voltage, attached to the section, and inversely proportionate to the section characteristics, called the electric resistance of the section.The power of current on the circuit section is equal to the relationship of the section voltage to the resistance. The Ohm's law for the electric circuit is as follows: i equals U on R or R equals U on i, where U is the voltage or voltage difference, i is the current power and R is resistance.To easily memorize the Ohm's law the following diagram in the way of a triangle may be drawn, i UR Close the sought-for value and the two other symbols will give you the formula to calculate it. Let us assemble the simplest ...