Chapter 15 Quiz: Lighting

Multiple Choice

1. A modern LED bulb producing 800 lumens uses approximately how many watts?

a) 60 watts b) 40 watts c) 8–10 watts d) 20 watts

Correct answer: c 800 lumens is the standard "60-watt equivalent" output. A good LED achieves this with 8–10 watts — an 85–90% efficiency improvement over incandescent.

2. Which color temperature would be MOST appropriate for a bedroom aiming for a warm, relaxing atmosphere?

a) 5000K (daylight) b) 4000K (cool white) c) 3500K (neutral white) d) 2700K (warm white)

Correct answer: d 2700K produces warm, yellow-toned light closest to incandescent — ideal for bedrooms and living spaces. Higher color temperatures (4000K+) feel clinical and are better suited to workshops.

3. A CRI of 90 on a light bulb means:

a) The bulb is 90% efficient compared to incandescent b) The bulb lasts 90,000 hours c) The bulb renders colors with 90% accuracy compared to natural sunlight d) The bulb produces 90 lumens per watt

Correct answer: c Color Rendering Index (CRI) measures how accurately a light source renders colors relative to natural sunlight (CRI 100). A CRI 90+ bulb renders colors with high fidelity — important in kitchens and bathrooms.

4. What does "IC rated" mean for a recessed light fixture?

a) The fixture has an integrated circuit for smart home control b) The fixture is safe for direct contact with insulation c) The fixture is rated for installation in concrete d) The fixture uses an indirect current power supply

Correct answer: b IC stands for "Insulation Contact." An IC-rated fixture is designed to be in direct contact with attic insulation without creating a fire hazard. Non-IC fixtures require 3 inches of clearance from all insulation.

5. You install new dimmable LED bulbs with your existing dimmer switch and they flicker at low settings and buzz. The MOST LIKELY cause is:

a) The bulbs are defective b) The circuit breaker is failing c) The dimmer is not compatible with LED loads d) The wiring gauge is too small for LED fixtures

Correct answer: c Dimmer/LED incompatibility is the most common cause of this exact symptom combination. The old dimmer was designed for resistive incandescent loads and doesn't handle the electronic drivers in LED bulbs properly. Solution: replace with an LED-compatible dimmer.

6. In summer, a ceiling fan in the correct setting should produce:

a) Air circulating upward along the walls b) A noticeable downward airflow felt directly below the fan c) Warm air distributed from ceiling level downward d) Minimal airflow in any direction

Correct answer: b Summer mode (counterclockwise/forward rotation) pushes air straight down, creating the wind chill effect that makes occupants feel cooler. This allows you to raise the thermostat without discomfort.

7. Which of the following is the correct action when multiple lights throughout the house flicker simultaneously, especially when large appliances cycle on?

a) Replace all the bulbs b) Reset the dimmer switches c) Call a licensed electrician — this may indicate a main panel or service entrance issue d) Replace the GFCI outlets on each circuit

Correct answer: c Whole-house flickering correlated with large appliance starts is a warning sign of a loose connection at the main panel, service entrance, or utility connection — a potentially serious issue requiring professional evaluation.

8. A non-IC recessed fixture installed in an insulated ceiling creates which TWO primary problems?

a) Reduced light output and buzzing noise b) Fire risk from heat buildup and excessive air leakage between conditioned and unconditioned space c) Incompatibility with LED bulbs and moisture infiltration d) Shortened bulb life and GFCI tripping

Correct answer: b Non-IC fixtures in insulated ceilings are both a fire hazard (the fixture generates enough heat to degrade or ignite insulation) and a major source of air leakage — essentially open holes in the ceiling allowing conditioned air to escape to the attic year-round.

9. A smart dimmer that says "requires neutral wire" likely won't work in:

a) Any room with more than one switch b) Older homes with switch loop wiring (two-wire circuits without a neutral at the switch location) c) Circuits with more than eight LED bulbs d) Any home built before 2000

Correct answer: b Many pre-1980s homes were wired with switch loops — a wiring method that routes only the hot wire to the switch and back, without a neutral conductor. Most smart dimmers require a neutral to power their electronics. Most manufacturers offer a "no-neutral" version for these situations.

10. A recessed light that turns off after 20–30 minutes of use and then comes back on after cooling is most likely:

a) On a GFCI-protected circuit that's tripping b) Triggering its built-in thermal protection cutout due to overheating c) Experiencing a loose bulb connection d) A sign the circuit breaker is failing

Correct answer: b Recessed fixtures have thermal protection that shuts them down if they overheat. Cycling on and off is the classic symptom. Causes include using the wrong bulb type, insulation packed against a non-IC fixture, or inadequate clearance. The fix: address the insulation clearance or install an IC-rated LED retrofit kit.

Short Answer

Short Answer 1: Explain the difference between lumens and watts, and why this distinction matters when shopping for LED bulbs.

Model answer: Watts measure energy consumption, not brightness. Lumens measure actual light output. Incandescent bulbs made watts a useful proxy because a 60W incandescent always produced about 800 lumens. LEDs break that relationship — a 9W LED also produces 800 lumens. Shopping by watts with LEDs would lead you to buy bulbs that are far too dim (9W looks inadequate compared to 60W, even though they produce the same light). Always compare bulbs by lumen output.

Short Answer 2: A homeowner wants to upgrade a bathroom vanity to improve their experience applying makeup and evaluating skin tone. What bulb specifications should they prioritize, and why?

Model answer: The homeowner should prioritize CRI 90+ (preferably 95+) for accurate color rendering — low CRI light makes skin tones look inaccurate and colors appear different from how they look outdoors. Color temperature should be 2700K–3000K to provide warm, flattering light similar to natural morning light. High CRI is the most important specification for this use case — it directly determines whether colors look accurate.

Short Answer 3: Describe the steps you would take to diagnose a ceiling fan that wobbles noticeably during operation.

Model answer: First, turn off the fan and ensure all blade brackets are tightly screwed to the motor housing — loose blade arms are a common cause. Second, check that all blades are tightly attached to their arms. Third, visually inspect whether any blade appears warped or bent differently from the others. Fourth, use a balancing kit (available for $5–10 at hardware stores) — clip the provided weight to blade tips one at a time to find the blade causing the imbalance, then apply the adhesive weight to the top surface at the location that eliminated wobble. If wobbling persists after balancing, check the fan mounting box to confirm it's fan-rated and securely mounted.