First-year review quiz

Check yourself

15 questions. Tap an answer — it is marked straight away and the reason opens under it. Get 80% or better and the lesson is ticked off on the year page.

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1. What does the harm in an electric shock mostly depend on?

   A The voltage alone B How much current flows through the body, which path it takes, and for how long C The colour of the wire D Whether it is AC or DC only
   Answer and why

   B. Current through the body does the damage — especially across the chest and heart — and time makes it worse. Voltage matters because it is what drives that current through your skin’s resistance. Safety lesson.

2. An arc flash is…

   A a small static spark B the light from a welding torch C an explosive release of heat and light when current jumps through the air between conductors D a tripped GFCI
   Answer and why

   C. An arc fault through air can reach temperatures far hotter than the sun’s surface in a fraction of a second, with a pressure blast and molten metal. That is what arc-rated PPE and de-energizing protect against.

3. A non-contact voltage tester stays silent near a conductor. That proves…

   A the conductor is dead B nothing — prove dead with a two-pole tester or meter, live–dead–live C the breaker is off D the neutral is open
   Answer and why

   B. Non-contact testers are a screen, not a proof. They miss live conductors in some conditions. Tools and testers.

4. Voltage is best described as…

   A the flow of electrons B the opposition to flow C the rate energy is used D the push — the difference in electrical pressure between two points
   Answer and why

   D. Voltage is potential difference: the push. Current is the flow, resistance the opposition, power the rate. What electricity is.

5. A 240 V heater element measures 60 Ω hot. What current does it draw?

   A 0.25 A B 4 A C 14,400 A D 300 A
   Answer and why

   B. I = V ÷ R = 240 ÷ 60 = 4 A.

6. A load draws 12 A at 120 V. What power?

   A 10 W B 132 W C 1,440 W D 144 W
   Answer and why

   C. P = V × I = 120 × 12 = 1,440 W.

7. Resistors of 10 Ω, 20 Ω and 30 Ω are in series across 120 V. What is the voltage across the 30 Ω one?

   A 60 V B 40 V C 20 V D 120 V
   Answer and why

   A. Total R = 60 Ω, so I = 120 ÷ 60 = 2 A everywhere. Across the 30 Ω: 2 × 30 = 60 V. (The drops are 20 + 40 + 60 = 120 V.) Series circuits.

8. Two 60 Ω resistors in parallel have a total resistance of…

   A 120 Ω B 60 Ω C 30 Ω D 15 Ω
   Answer and why

   C. Two equal resistors in parallel: half of one, 30 Ω. The total is always less than the smallest branch. Parallel circuits.

9. A 10 Ω resistor in series with two 20 Ω resistors that are in parallel with each other. Total resistance?

   A 50 Ω B 20 Ω C 30 Ω D 5 Ω
   Answer and why

   B. Reduce the parallel pair first: 20 ‖ 20 = 10 Ω. Then the series: 10 + 10 = 20 Ω. Combination circuits.

10. Same conductor, run twice as far. Its resistance…

    A doubles B halves C stays the same D quadruples
    Answer and why

    A. Resistance is proportional to length. Conductors and insulation.

11. On a plan drawn at 1/4" = 1'-0", a run measures 3" on the paper. How long is it?

    A 3 ft B 0.75 ft C 12 ft D 48 ft
    Answer and why

    C. One inch on paper is 4 ft, so 3" is 12 ft. Reading prints.

12. A conductor goes around a terminal screw…

    A counter-clockwise B either way C clockwise, the way the screw tightens D with no hook at all
    Answer and why

    C. Clockwise, so tightening pulls it in. Terminations.

13. Why is bonding, not the ground rod, what trips a breaker on a fault to a metal case?

    A Bonding is green B Bonding gives a low-resistance metal path back to the source, so a large fault current flows C The ground rod is only for 240 V D Breakers read the earth’s voltage
    Answer and why

    B. Through the earth the resistance is too high for enough current to flow. A bonded path carries many times the breaker rating. Grounding and bonding.

14. A GFCI trips when…

    A the circuit draws more than its rating B it detects arcing C the voltage is low D the current out on the hot and back on the neutral differ by a few milliamps
    Answer and why

    D. It compares out and back; a difference means current is leaking another way, possibly through someone. Residential circuits.

15. The correct order to prove a circuit dead is…

    A test the circuit only B test a known live source, test the circuit, test the known live source again C test the circuit twice D use a non-contact tester, then touch it
    Answer and why

    B. Live–dead–live proves the meter worked before and after. Using your meter.