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Subelement B-005

B-005

Section B-005-005

Section B-005-005

In a parallel circuit with a voltage source and several branch resistors, how is the total current related to the current in the branch resistors?

  • Correct Answer
    It equals the sum of the branch current through each resistor
  • It equals the average of the branch current through each resistor
  • It decreases as more parallel resistors are added to the circuit
  • It is the sum of each resistor's voltage drop multiplied by the total number of resistors

Each resistor added in parallel to the source draws some current ( in accordance with Ohm's Law, I = E / R ). The total current that the source must supply becomes the SUM of all these individual currents. Just like in your house, the total current drawn from the utility company is the sum of all the devices turned on.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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You connect four 100-ohm resistors in parallel across a 12-volt battery. How many milliamperes of current are drawn from the battery?

  • 48 mA
  • 240 mA
  • 120 mA
  • Correct Answer
    480 mA

Key word: PARALLEL. In a parallel circuit, the total current is the sum of the currents. All resistors are subjected to the same voltage in a PARALLEL circuit. Total current is four times the current through a single resistor, 4 * ( 12 / 100 ). Total current can also be seen as the current through a resistor with one fourth the value of a single resistor, 12 / 25.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Several resistors of various values are connected in parallel. How does the total resistance of the combination compare to the individual resistors?

  • It is greater than the largest resistor
  • It equals the average of the resistors
  • It equals the square root of the sum of the resistors
  • Correct Answer
    It is less than the smallest resistor

Key word: PARALLEL. In a parallel circuit, each added resistor adds to the current drawn from the source. If more and more current is drawn, the total resistance must be going down. In PARALLEL, the total resistance is less than the smallest.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Two 1000-ohm resistors are connected in parallel across a 12-volt battery. What is the total current?

  • 12 milliamperes
  • Correct Answer
    24 milliamperes
  • 60 milliamperes
  • 120 milliamperes

Ohm's Law ( I = E / R ). Each resistor draws this much current: 12 volts divided by 1000 ohms = 0.012 amperes = 12 milliamperes. In PARALLEL, total current is the sum of the currents. Method B: identical resistors in parallel, total resistance is value divided by number. In this case, 1000 / 2 = 500 ohms. 12 volts / 500 ohms = 0.024 amperes = 24 milliamperes.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The total resistance of resistors connected in series is:

  • less than the resistance of any one resistor
  • Correct Answer
    greater than the resistance of any one resistor
  • equal to the lowest resistance present
  • equal to the highest resistance present

Key word: SERIES. In a series circuit, there is only one current. This current must wrestle with each resistor one after the other. In SERIES, total resistance is the sum of the resistance values. The same current flows through all of them.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is the total resistance of five 10-ohm resistors in series?

  • 2 ohms
  • 5 ohms
  • Correct Answer
    50 ohms
  • 10 ohms

Key word: SERIES. In SERIES, total resistance is the sum of the resistance values.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Which of these series combination of resistors would replace a single 120-ohm resistor?

  • Six 22-ohm resistors
  • Correct Answer
    Five 24-ohm resistors
  • Two 240-ohm resistors
  • Five 100-ohm resistors

Key word: SERIES. In SERIES, total resistance is the sum of the resistance values. Five times twenty-four = 120.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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If ten resistors of equal value "R" are wired in parallel, what formula yields the total resistance?

  • 10 / R
  • Correct Answer
    R / 10
  • 10 x R
  • 10 + R

Key word: PARALLEL. In a parallel circuit with IDENTICAL resistors, total resistance is value divided by number. In this example, the value of one R divided by 10.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What is the total resistance of four 68-ohm resistors wired in parallel?

  • 12 ohms
  • 34 ohms
  • Correct Answer
    17 ohms
  • 272 ohms

Key word: PARALLEL. In a parallel circuit with IDENTICAL resistors, total resistance is value divided by number. In this example, 68 / 4 yields 17.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Two resistors are in parallel. Resistor "A" carries twice the current of resistor "B," which means that:

  • "B" has half the resistance of "A"
  • Correct Answer
    "A" has half the resistance of "B"
  • the voltage across "A" is twice that across "B"
  • the voltage across "B" is twice that across "A"

Key word: PARALLEL. All resistors in a parallel circuit are subjected to the same voltage. Per Ohm's Law ( I = E / R, current = voltage divided by resistance ), if resistor A draws twice the current of resistor B, it must have half the resistance of Resistor B.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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The total current in a parallel circuit is equal to the:

  • current in any one of the parallel branches
  • source voltage divided by the value of one of the resistive elements
  • source voltage divided by the sum of the resistive elements
  • Correct Answer
    sum of the currents through all the parallel branches

Key word: PARALLEL. In a parallel circuit, the total current is the sum of the currents. Each branch is subjected to the same voltage and draws a current in accordance with Ohm's Law ( I = E / R, current = voltage divided by resistance ).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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