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T5D03

ELECTRICAL PRINCIPLES · Ohm's Law; Series and parallel circuits

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What formula is used to calculate resistance in a circuit?

  1. AR = E x I
  2. BR = E / I
  3. CR = E + I
  4. DR = E - I
Why Ohm's Law relates voltage (E), current (I) and resistance (R) as E = I x R. Solving that for resistance means dividing both sides by current, giving R = E / I. So if 12 volts pushes 3 amps through a component, its resistance is 12 / 3 = 4 ohms.
Watch out Multiplying voltage by current, E x I, is the power formula (watts), not resistance. Adding or subtracting volts and amps is meaningless since they are different units.
Ohm's triangle: E on top, I and R below. Cover R and you see E over I.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of T5D

  1. T5D01 What formula is used to calculate current in a circuit?
  2. T5D02 What formula is used to calculate voltage in a circuit?
  3. T5D03 What formula is used to calculate resistance in a circuit?
  4. T5D04 What is the resistance of a circuit in which a current of 3 amperes flows when connected to 90 volts?
  5. T5D05 What is the resistance of a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amp…
  6. T5D06 What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
  7. T5D07 What is the current in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
  8. T5D08 What is the current through a 100-ohm resistor connected across 200 volts?
  9. T5D09 What is the current through a 24-ohm resistor connected across 240 volts?
  10. T5D10 What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
  11. T5D11 What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
  12. T5D12 What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
  13. T5D13 In which type of circuit is the current always the same through all components?
  14. T5D14 In which type of circuit is the voltage always the same across all components?
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