A room is 120 feet by 60 feet with 16 feet ceiling. A luminaire is suspended 4 feet below the ceiling and the work plane is 4 feet above the floor. The value of room cavity ratio (RCR) is
Answer & step-by-step solution
The luminaire is 4 ft below a 16-ft ceiling and the work plane is 4 ft above the floor, so cavity height is 8 ft. Room cavity ratio is RCR=5h(L+W)/(LW). Substituting h=8 ft, L=120 ft and W=60 ft gives RCR=1.0, matching option B.
Concept and Reasoning
The luminaire is 4 ft below a 16-ft ceiling and the work plane is 4 ft above the floor, so cavity height is 8 ft. Room cavity ratio is RCR=5h(L+W)/(LW). Substituting h=8 ft, L=120 ft and W=60 ft gives RCR=1.0, matching option B.
Calculation / Key Relation
RCR=5h(L+W)/(LW)=5×8×180/(120×60)=1.0
Exam Takeaway
Use the vertical distance from luminaire plane to work plane as cavity height.
Common Mistake
Do not use the full ceiling height as h when luminaires are suspended and a work plane is specified.
Quick Trick
Use the vertical distance from luminaire plane to work plane as cavity height.
एक कमरा 120 फुट × 60 फुट का है और छत 16 फुट ऊँची है। ल्यूमिनेयर छत से 4 फुट नीचे लटका है और कार्य तल फर्श से 4 फुट ऊपर है। रूम कैविटी अनुपात (RCR) का मान है
उत्तर और चरणबद्ध हल
B — 1। कैविटी ऊँचाई h = 16 − 4 − 4 = 8 ft। RCR = 5h(L + W)/(LW) = 5×8×180/(120×60) = 7200/7200 = 1।
विस्तृत हल (मूल भाषा में)
Concept and Reasoning
The luminaire is 4 ft below a 16-ft ceiling and the work plane is 4 ft above the floor, so cavity height is 8 ft. Room cavity ratio is RCR=5h(L+W)/(LW). Substituting h=8 ft, L=120 ft and W=60 ft gives RCR=1.0, matching option B.
Calculation / Key Relation
RCR=5h(L+W)/(LW)=5×8×180/(120×60)=1.0
Exam Takeaway
Use the vertical distance from luminaire plane to work plane as cavity height.
Common Mistake
Do not use the full ceiling height as h when luminaires are suspended and a work plane is specified.
Quick Trick
Use the vertical distance from luminaire plane to work plane as cavity height.
એક ઓરડો 120 ફૂટ × 60 ફૂટનો છે અને છત 16 ફૂટ ઊંચી છે. લ્યુમિનેર છતથી 4 ફૂટ નીચે લટકેલું છે અને કાર્ય સમતલ ભોંયતળિયાથી 4 ફૂટ ઉપર છે. રૂમ કેવિટી ગુણોત્તર (RCR)નું મૂલ્ય છે
જવાબ અને પગલાવાર ઉકેલ
B — 1. કેવિટી ઊંચાઈ h = 16 − 4 − 4 = 8 ft. RCR = 5h(L + W)/(LW) = 5×8×180/(120×60) = 7200/7200 = 1.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Concept and Reasoning
The luminaire is 4 ft below a 16-ft ceiling and the work plane is 4 ft above the floor, so cavity height is 8 ft. Room cavity ratio is RCR=5h(L+W)/(LW). Substituting h=8 ft, L=120 ft and W=60 ft gives RCR=1.0, matching option B.
Calculation / Key Relation
RCR=5h(L+W)/(LW)=5×8×180/(120×60)=1.0
Exam Takeaway
Use the vertical distance from luminaire plane to work plane as cavity height.
Common Mistake
Do not use the full ceiling height as h when luminaires are suspended and a work plane is specified.
Quick Trick
Use the vertical distance from luminaire plane to work plane as cavity height.
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