Technician T5D: Ohm's law, series and parallel
These are the 14 official questions in group T5D of the 2026–2030 Technician question pool, with the correct answer marked and a plain-English explanation of why it's right. The real exam asks one question from this group.
- T5D01Question 1
What formula is used to calculate current in a circuit?
- AI = E x R
- BI = E / R Correct
- CI = E2 x R
- DI = E2 / R
Why: Current = voltage ÷ resistance: I = E / R.
- T5D02Question 2
What formula is used to calculate voltage in a circuit?
- AE = I x R Correct
- BE = I / R
- CE = I2 x R
- DE = I2 / R
Why: Voltage = current × resistance: E = I × R.
- T5D03Question 3
What formula is used to calculate resistance in a circuit?
- AR = E x I
- BR = E / I Correct
- CR = E + I
- DR = E - I
Why: Resistance = voltage ÷ current: R = E / I.
- T5D04Question 4
What is the resistance of a circuit in which a current of 3 amperes flows when connected to 90 volts?
- A3 ohms
- B30 ohms Correct
- C1/30 ohm
- D270 ohms
Why: R = 90 V ÷ 3 A = 30 Ω.
- T5D05Question 5
What is the resistance of a circuit for which the applied voltage is 12 volts and the current flow is 1.5 amperes?
- A18 ohms
- B0.125 ohms
- C8 ohms Correct
- D13.5 ohms
Why: R = 12 V ÷ 1.5 A = 8 Ω.
- T5D06Question 6
What is the resistance of a circuit that draws 4 amperes from a 12-volt source?
- A3 ohms Correct
- B16 ohms
- C48 ohms
- D8 ohms
Why: R = 12 V ÷ 4 A = 3 Ω.
- T5D07Question 7
What is the current in a circuit with an applied voltage of 120 volts and a resistance of 80 ohms?
- A9600 amperes
- B200 amperes
- C0.667 amperes
- D1.5 amperes Correct
Why: I = 120 V ÷ 80 Ω = 1.5 A.
- T5D08Question 8
What is the current through a 100-ohm resistor connected across 200 volts?
- A20,000 amperes
- B0.5 amperes
- C2 amperes Correct
- D100 amperes
Why: I = 200 V ÷ 100 Ω = 2 A.
- T5D09Question 9
What is the current through a 24-ohm resistor connected across 240 volts?
- A2400 amperes
- B0.1 amperes
- C10 amperes Correct
- D5760 amperes
Why: I = 240 V ÷ 24 Ω = 10 A.
- T5D10Question 10
What is the voltage across a 2-ohm resistor if a current of 0.5 amperes flows through it?
- A1 volt Correct
- B0.25 volts
- C2.5 volts
- D1.5 volts
Why: E = 0.5 A × 2 Ω = 1 V.
- T5D11Question 11
What is the voltage across a 10-ohm resistor if a current of 1 ampere flows through it?
- A1 volt
- B10 volts Correct
- C11 volts
- D9 volts
Why: E = 1 A × 10 Ω = 10 V.
- T5D12Question 12
What is the voltage across a 10-ohm resistor if a current of 2 amperes flows through it?
- A8 volts
- B0.2 volts
- C12 volts
- D20 volts Correct
Why: E = 2 A × 10 Ω = 20 V.
- T5D13Question 13
In which type of circuit is the current always the same through all components?
- ASeries Correct
- BParallel
- CResonant
- DBranch
Why: In a series circuit there's only one path, so the same current flows through every part.
- T5D14Question 14
In which type of circuit is the voltage always the same across all components?
- ASeries
- BParallel Correct
- CResonant
- DBranch
Why: In a parallel circuit every part is connected across the same two points, so the voltage is the same.