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MCQ Practice Test — Category 08
Circuit Breaker & Protection MCQ
MCB, MCCB, RCBO, ACB — types, ratings, trip curves aur selection. Gulf panel me har cheez yahi decide karti hai.
50 Questions
Easy-Hard Level
Hinglish Explanation
Attempted: 0/50
Correct: 0
Wrong: 0
Question 01Easy
MCB aur MCCB me kya main fark hai?
AKoi fark nahi
BMCB up to 63A fixed trip, MCCB 100A-2500A adjustable trip
CMCCB sirf DC ke liye hai
DMCB size me bada hota hai
✓ Sahi Jawab: B
MCB: 63A tak, fixed trip settings, residential/commercial ke liye. MCCB: 100A-2500A, adjustable thermal + magnetic trip, main incomer me lagta hai. Gulf me main DB incomer pe hamesha MCCB ya ACB lagta hai.
Question 02Easy
RCCB aur MCB me kya fark hai?
ADono same kaam karte hain
BRCCB overload se protect karta hai
CRCCB earth leakage detect karta hai, MCB overload/short circuit rokta hai
DMCB earth leakage detect karta hai
✓ Sahi Jawab: C
MCB = overload + short circuit protection. RCCB = earth fault/leakage protection (jaise 30mA). RCCB overload se nahi bachata. RCBO in dono ka combination hai aur Gulf me bahut use hota hai.
Question 03Medium
Type B, C, aur D MCB me kya fark hai?
AMagnetic trip limit: B=3-5x, C=5-10x, D=10-20x FLC
BSirf color coding ka fark hai
CKoi technical fark nahi hai
DType D gharon ke liye hota hai
✓ Sahi Jawab: A
Type B (3-5x): Resistive loads, normal lighting. Type C (5-10x): Motors, AC (inrush current handle karta hai). Type D (10-20x): Welding machines jaise high inrush load. Industrial motor ke liye Type C zaruri hai.
Question 04Medium
MCB ki Breaking Capacity (Icn) ka kya matlab hai?
ANormal load current
BMCB ka physical size
CMaximum voltage
DMaximum short circuit current jo MCB safely interrupt kar sake bina jale
✓ Sahi Jawab: D
Breaking capacity ka matlab hai maximum fault current jo MCB safe tarike se clear kar sake. Gharon me 6kA aur commercial panels me 10kA+ breaking capacity wale MCB lagte hain.
Question 05Medium
Agar MCB bina kisi overload ke trip ho raha hai, toh kya karna chahiye?
AMCB turant replace kar do
BLoose connection, harmonics, moisture ya earth leakage check karo
CBadi rating ka MCB laga do
DKuch mat karo
✓ Sahi Jawab: B
Nuisance (faltu) tripping ke causes: Loose connection (jis se heat banti hai), harmonics, panel me moisture, ya galat curve type (jaise motor pe Type B lagana). Bina fault dhunde MCB change mat karo.
Question 06Medium
Breaker coordination me ‘Selectivity’ (Discrimination) ka kya matlab hai?
ASaare breaker ek sath trip ho jayein
BSabse sasta breaker select karna
CFault aane par sirf wahi breaker trip ho jo fault ke sabse kareeb ho
DPanel me sab breaker same rating ke hon
✓ Sahi Jawab: C
Selectivity se power loss kam hota hai. Agar kisi ek room ki light me short circuit ho, toh sirf us room ka 10A MCB gire, na ki main panel ka 100A MCCB. Hospitals aur Data Centers me ye bahut zaruri hai.
Question 07Hard
20A MCB se protected circuit me 3kW, 230V single phase load ka kya asar hoga?
ASafe hai — load current 13A hai jo 20A se kam hai
BMCB turant trip ho jayega
CCable jal jayegi
DBahut zyada voltage drop hoga
✓ Sahi Jawab: A
I = P/V = 3000/230 = 13.04A. Ek 20A ka MCB is continuous load ko safely chala lega bina trip hue.
Question 08Hard
ACB (Air Circuit Breaker) ka use kahan hota hai?
AGhar ke chote DB me
BHigh current applications (800A-6300A) me jaise main incomer aur bus coupler
CSirf outdoor overhead lines ke liye
DSirf direct motor protection ke liye
✓ Sahi Jawab: B
ACB badi commercial buildings ke main LV switchgear me use hote hain jo bahut high current (6300A tak) handle karte hain. Inme advanced electronic trip units (Micrologic/Ekip) hoti hain.
Question 09Medium
Thermal-magnetic MCB me ‘Thermal element’ kya detect karta hai?
AShort circuit
BEarth leakage
CVoltage surge
DOverload (slow sustained overcurrent)
✓ Sahi Jawab: D
Thermal element (bimetallic strip) overload ki wajah se heat ho kar bend hoti hai aur breaker ko trip karti hai. Short circuit ke liye andar magnetic coil hoti hai jo instant trip karti hai.
Question 10Hard
3-Phase 415V, 50kW load ke liye breaker rating kya honi chahiye? (PF=0.85)
A50A
B63A
C100A
D125A
✓ Sahi Jawab: C
I = P / (√3 × V × PF) = 50000 / (1.732 × 415 × 0.85) = 81.8A. 81.8A ke upar ka standard commercial breaker size 100A MCCB hota hai.
Question 11Medium
RCBO ka full form kya hota hai?
A. Residual Current Breaker Only
B. Residual Current Breaker with Overcurrent protection
C. Relay Controlled Breaker Output
D. Remote Circuit Breaker Operation
✓ Sahi Jawab: B
Ek RCBO me MCB (overload/short-circuit) aur RCCB (earth leakage) dono ke features ek hi device me hote hain, is se DB me jagah bachti hai.
Question 12Hard
Purane ELCB aur naye RCCB me kya practical fark hai?
A. ELCB voltage-operated hai, RCCB current-operated hai
B. ELCB DC ke liye tha, RCCB AC ke liye hai
C. Koi fark nahi, bas naam badla gaya hai
D. RCCB voltage-operated hai, ELCB current-operated hai
✓ Sahi Jawab: A
Purane ELCB earth wire par voltage detect karte the. Naye RCCB Current Transformer ka use karke Phase aur Neutral ke current ka difference (imbalance) napte hain. ELCB ab obsolete (band) ho chuke hain.
Question 13Easy
Human life protection (insan ki jaan bachane) ke liye RCCB ki standard sensitivity kya honi chahiye?
A. 100mA
B. 300mA
C. 30mA
D. 500mA
✓ Sahi Jawab: C
Ghar ke sockets aur bathroom me 30mA rating mandatory hai. Ye itni jaldi trip hota hai ki insan ko fatal electric shock (jaanlewa jhatka) nahi lagta. 300mA sirf aag se bachav (fire protection) ke liye hota hai.
Question 14Medium
VCB (Vacuum Circuit Breaker) kahan install kiya jata hai?
A. Ghar ki lighting circuits me
B. Low Voltage (415V) main incomer me
C. DC battery banks me
D. Medium Voltage (11kV se 33kV) switchgear me
✓ Sahi Jawab: D
VCB me arc ko bujhane ke liye vacuum ka use hota hai. Ye bahut fast aur compact hote hain, isliye inhe Medium Voltage (MV) networks jaise 11kV substations me use kiya jata hai.
Question 15Hard
AFDD kis cheez se bachata hai jo MCB ya RCCB nahi kar sakte?
A. Phase-to-phase short circuit se
B. Loose wiring me hone wale electrical arcs (sparking) se, aag lagne ko rokta hai
C. Bijli girne (Lightning strikes) se
D. Voltage up-down (fluctuations) se
✓ Sahi Jawab: B
Arc Fault Detection Device (AFDD) microprocessor ka use karke deewar ke andar chhupi kharab wire ki sparking (arc) detect kar leta hai aur aag lagne se pehle trip ho jata hai.
Question 16Medium
Breaker me ‘Shunt Trip coil’ ka kya kaam hota hai?
A. Breaker ko electrical signal bhej kar remote se trip karwana
B. Voltage 70% se kam hone par trip karna
C. Breaking capacity ko badhana
D. Earth fault detect karna
✓ Sahi Jawab: A
Shunt Trip ek accessory hai jisme voltage dene par wo breaker ko trip kara deti hai. Aag lagne par Fire Alarm Panel isko signal bhejta hai taaki main power cut ho jaye.
Question 17Medium
Breaker setup me UVR (Under Voltage Release) kya karta hai?
A. Voltage dip hone par usko badhata (boost) hai
B. High voltage aane par breaker trip karta hai
C. Agar supply fail ho jaye ya voltage bahut kam ho jaye toh breaker trip kar deta hai
D. Electricity consumption (unit) napta hai
✓ Sahi Jawab: C
UVR motors ko low voltage pe chalne se bachata hai. Agar power chali jaye toh ye breaker gira deta hai, taaki jab power wapas aaye toh motor apne aap start na ho jaye (safety reason).
Question 18Easy
Kya MCB ko daily lighting switch ki tarah ON/OFF karne ke liye use karna sahi hai?
A. Haan, hamesha kar sakte hain
B. Nahi, roz manual ON/OFF karne se iska internal mechanism jaldi kharab ho jata hai
C. Sirf Type B ko switch ki tarah use kar sakte hain
D. Haan, par sirf DC me
✓ Sahi Jawab: B
MCB ek protection device hai, normal switch nahi. Isko bar-bar up-down karne se iske contacts ghis jate hain aur protection fail ho sakti hai. Lighting control ke liye contactor ya normal switch use karo.
Question 19Hard
Industrial circuit breakers (jaise MCCB aur ACB) ka IEC standard kaun sa hai?
A. IEC 60898
B. IEC 61439
C. IEC 60947-2
D. IEC 60364
✓ Sahi Jawab: C
IEC 60947-2 industrial breakers ke liye hota hai. IEC 60898 gharon me lagne wale normal MCB ke liye hota hai jise aam aadmi operate kar sake.
Question 20Hard
MCCB ki nameplate par ‘Ics’ aur ‘Icu’ ka kya matlab hota hai?
A. Icu = Ultimate breaking capacity, Ics = Service breaking capacity
B. Icu = Under current, Ics = Short circuit current
C. Dono ka exact same matlab hai
D. Ye breaker ka physical size batate hain
✓ Sahi Jawab: A
Icu wo max fault hai jo breaker ek baar clear kar dega (par uske baad shayad kharab ho jaye). Ics wo fault hai jo wo bina kharab hue kai baar clear kar sakta hai. Achhe breakers me Ics = 100% Icu hota hai.
Question 21Medium
MPCB ka use kis liye kiya jata hai?
A. Lighting control ke liye
B. Motor Protection (Overload, short circuit, aur phase loss) ke liye
C. Main incoming panel me
D. Earthing network ke liye
✓ Sahi Jawab: B
Motor Protection Circuit Breakers (MPCB) motors ke high starting current ko bina trip hue handle karte hain aur purane OLR (Overload Relay) ki jagah kaam aate hain.
Question 22Medium
Agar 3-phase circuit me 4-pole MCB lagaya jaye, toh chautha (4th) pole kya disconnect karta hai?
A. Earth
B. Backup Phase
C. Control circuit
D. Neutral
✓ Sahi Jawab: D
4-pole breaker 3 Phases (R, Y, B) ke sath Neutral ko bhi cut karta hai. Maintainance ke time isse poori tarah isolation milta hai, khaaskar TT earthing system me.
Question 23Easy
RCCB me laga ‘T’ (Test) button kitni baar dabana chahiye?
A. Daily
B. Kabhi nahi, is se RCCB kharab ho jayega
C. Regularly (jaise har mahine ya quarter me)
D. Sirf lagate waqt
✓ Sahi Jawab: C
Test button ek nakli (artificial) leakage create karta hai taaki check ho sake ki trip mechanism kaam kar raha hai ya nahi. Ise har mahine dabana chahiye.
Question 24Hard
EV chargers aur Solar Inverters ke liye kaun se Type ka RCCB lagana mandatory hai?
A. Type B
B. Type AC
C. Type A
D. Type F
✓ Sahi Jawab: A
Type B RCCBs smooth DC leakage current ko pakad sakte hain jo EV charger aur inverter me nikalta hai. Normal Type AC aise DC fault me andha (blind) ho jata hai aur trip nahi karta.
Question 25Medium
Electrical panels me ‘Cascading’ ka kya matlab hai?
A. Breakers ko ulta lagana
B. Bahut sare neutral ek sath jodna
C. Upstream main breaker ki madad se chhote downstream breaker ko bade fault se bachana
D. Panel me pani aana
✓ Sahi Jawab: C
Cascading (Back-up protection) technique me bada MCCB current ko limit kar deta hai, isliye aage saste aur kam kA rating wale MCB use kiye ja sakte hain panel ki cost bachane ke liye.
Question 26Hard
ACB maintenance ke time “Rack Out” position ka kya matlab hai?
A. Breaker ON hai
B. Breaker live busbar se physically bahar nikal liya gaya hai taaki safely kaam ho sake
C. Breaker test mode me hai
D. Breaker trip ho gaya hai
✓ Sahi Jawab: B
Draw-out type ACB ko handle ghumakar panel se bahar khincha ja sakta hai. Rack Out / Withdrawn position me busbar aur ACB ke beech gap ban jata hai jo maintenance ke liye safe hai.
Question 27Medium
Earth wire ko kabhi bhi RCCB/RCBO ke andar se kyu nahi guzarna chahiye?
A. Ye leakage current ko cancel kar dega aur RCCB kabhi trip nahi karega
B. RCCB bar-bar trip hone lagega
C. Is se short circuit ho jayega
D. Earth wire cut jayegi
✓ Sahi Jawab: A
Agar Phase ka leakage current Earth wire se wapas ussi sensor me chala gaya, toh CT (sensor) ko lagega ki jitna current gaya utna wapas aa gaya. Is se RCCB fault me bhi andha ho jayega.
Question 28Easy
Electrical safety me LOTO (Lock Out, Tag Out) kya hai?
A. Line Off, Trip On
B. Load Output Test Operation
C. Leave Open To Observe
D. Breaker ko OFF karke uspe taala (padlock) aur warning tag lagana
✓ Sahi Jawab: D
LOTO ek bohut zaruri safety rule hai. Jab koi electrician line par kaam kar raha ho, toh breaker OFF karke uspe padlock laga dete hain taaki koi galti se bhi breaker ON na kar de.
Question 29Hard
Breaker par likhi ‘Uimp’ rating ka kya matlab hota hai?
A. Normal working voltage
B. Minimum voltage jispe wo chalega
C. Impulse withstand voltage (Bijli girne se aane wala jhatka sehne ki taqat)
D. Phase to Phase voltage
✓ Sahi Jawab: C
Uimp batata hai ki breaker ka insulation milliseconds ke liye kitna bada voltage spike jhel sakta hai (jaise 8kV) bina blast hue.
Question 30Medium
Naya lagaya gaya RCCB load chalu karte hi turant trip kar jata hai. Sabse bada karan kya ho sakta hai?
A. Voltage bahut zyada hai
B. Aage wiring me Neutral aur Earth wire aapas me touch ho rahe hain ya ulte jude hain
C. Load ampere limit se zyada le raha hai
D. MCB kharab hai
✓ Sahi Jawab: B
Agar breaker ke aage Neutral aur Earth mix/touch ho jayein, toh return current Neutral ke bajaye Earth se wapas aata hai. RCCB ko lagega ki current leak ho gaya aur wo turant trip ho jayega.
Question 31Easy
Kya MCB ek insan ko jaanlewa electric shock lagne se bacha sakta hai?
A. Nahi, MCB bahut heavy current pe trip karta hai, tab tak insan ki maut ho sakti hai
B. Haan, hamesha bachata hai
C. Sirf Type B MCB bacha sakta hai
D. Haan, agar 32A ka laga ho
✓ Sahi Jawab: A
Insan ko fatal shock 30mA (0.03 Amp) me lag jata hai. MCB toh 10 Amp ya 20 Amp ke baad trip hota hai. Isiliye shock se bachne ke liye RCCB/RCBO lagana hi padta hai.
Question 32Medium
Breaker me ‘Trip-Free’ feature ka kya matlab hota hai?
A. Ye load aane pe kabhi trip nahi hota
B. Trip hone ke baad apne aap ON ho jata hai
C. Bina light ke bhi trip ho jata hai
D. Agar aap handle ko zabardasti upar pakad ke bhi rakhein, toh bhi fault aane pe andar se trip ho jayega
✓ Sahi Jawab: D
Trip-Free ek safety feature hai. Koi bewakoof agar short circuit me handle ko tape mar de ya pakad ke rakhe, tab bhi internal contacts khul jayenge aur line cut jayegi.
Question 33Hard
Breaker trip curve me ‘IDMT’ ka kya matlab hota hai?
A. Instantaneous Direct Motor Trip
B. Internal Default Magnetic Trip
C. Inverse Definite Minimum Time (Jitna bada fault, utni jaldi trip)
D. Induced Direct Maximum Temperature
✓ Sahi Jawab: C
IDMT ka sidha rule hai: Agar thoda sa overload hai toh trip hone me 1 ghanta lagega, agar bahut bada overload hai toh 5 second me trip ho jayega. Ye cable ko bachane ke liye hota hai.
Question 34Medium
MCB aur MCCB ke andar ‘Arc Chute’ ka kya kaam hota hai?
A. Plastic body ko thanda rakhna
B. Short circuit ke time banne wali aag/spark (arc) ko tod kar thanda karke bujhana
C. Voltage check karna
D. Bimetal strip ko pakad ke rakhna
✓ Sahi Jawab: B
Jab full fault pe contacts khulte hain, toh andar bhayankar plasma ki chingari banti hai. Arc chute me lohe ki plates hoti hain jo us chingari ko chote tukdo me baat kar bujha deti hain.
Question 35Easy
Gulf ke normal residential DB (Distribution Board) me connection ka sahi sequence kya hota hai?
A. Main Isolator → RCCB → Single Pole MCBs
B. MCBs → Main Isolator → RCCB
C. RCCB → MCB → Isolator
D. DB me sirf MCB lagte hain
✓ Sahi Jawab: A
Main power pehle Isolator (Switch) me aati hai, wahan se leak protection ke liye RCCB me jati hai, aur phir alag-alag rooms ke liye busbar ke zariye MCBs me bant jati hai.
Question 36Medium
Inme se kaun sa valid MCB Curve type NAHI hai?
A. Type B
B. Type C
C. Type D
D. Type X
✓ Sahi Jawab: D
IEC standard curves B, C, aur D hote hain. Kuch special industrial model me K aur Z aate hain, lekin Type X jaisa kuch nahi hota.
Question 37Hard
MCCB ke sath EFR (Earth Fault Relay) aur CBCT kyu lagaya jata hai?
A. MCCB ko replace karne ke liye
B. Breaking capacity badhane ke liye
C. Badi machines ke liye adjustable earth leakage protection dene ke liye
D. Panel ko thanda rakhne ke liye
✓ Sahi Jawab: C
Bade current walo ke liye RCCB nahi aate. Wahan main cables ko CBCT (Core Balance CT) ke andar se nikalte hain. Leakage hone pe EFR relay MCCB ke Shunt coil ko signal dekar trip kara deti hai.
Question 38Medium
Kya ek single MCB terminal ke andar bahut sari taarein (wires) ghusa kar tighten karna theek hai?
A. Haan, jitni fit aa jayein
B. Bilkul nahi, aamtaur pe max 2 same size ki wire, warna terminal block/connector use karein
C. Haan, par sirf Earth wire ke liye
D. Bas taar ko twist karke lagana zaruri hai
✓ Sahi Jawab: B
Alag-alag motayi (size) ki tarain ek hole me dalne se loose connection banta hai, jis se sparking hoti hai aur aag lag sakti hai. Hamesha proper distribution blocks ya din rail terminal use karne chahiye.
Question 39Easy
Agar 10A ke MCB se lagatar 11A current ja raha hai, toh wo kab trip karega?
A. Bahut der baad (shayad kuch ghante me)
B. Ek second me
C. Exactly 5 second me
D. Kabhi nahi
✓ Sahi Jawab: A
MCB me ek non-tripping limit hoti hai (jaise 1.13 guna zyada). 10A pe 11A aane se heat bahut dheere banegi, isliye trip hone me ghanto lag sakte hain. Ye ek standard IDMT feature hai.
Question 40Hard
Circuit breaker ki “Making Capacity” ka kya matlab hai?
A. Breaking capacity jaisa hi hota hai
B. Breaker ko banane (manufacture) ki limit
C. Short circuit chalte hue aage agar aap galti se breaker ON kar do, toh bina contacts weld (chipakne) hue safe chalne ki taqat
D. Minimum current chalu hone ke liye
✓ Sahi Jawab: C
Agar short circuit maujud ho aur aap manual handle upar karein, toh bahut bhayankar jhatka lagta hai jo contacts ko chipka (weld) sakta hai. Making capacity ensure karti hai ki breaker aise worst-case me bhi safely close ho sake.
Question 41Medium
High voltage circuit breakers me aag (arc) bujhane ke liye kaun si Gas use hoti hai?
A. Oxygen
B. SF6 (Sulfur Hexafluoride)
C. Helium
D. Methane
✓ Sahi Jawab: B
SF6 gas bahut badhiya insulator hoti hai aur aag bujhane (arc quenching) me mahir hoti hai. Substations ke GIS (Gas Insulated Switchgear) me yahi bhari hoti hai.
Question 42Easy
Breaker ka size sirf Load ke hisab se nahi, balki Cable ke hisab se kyu fix kiya jata hai?
A. Paise bachane ke liye
B. Wiring aasan hoti hai
C. Koi fark nahi padta
D. Kyunki Breaker ka main kaam cable ke insulation ko jalne se bachana hai
✓ Sahi Jawab: D
Golden Rule: Load Current ≤ Breaker Rating ≤ Cable Capacity. Agar aapne patli 1.5 sqmm wire pe 32A ka MCB laga diya, toh pehle taar jal ke raakh ho jayegi, MCB girega hi nahi.
Question 43Hard
Badi motor panels me purane OLR ki jagah ‘Electronic Motor Protection Relay’ ka kya fayda hai?
A. Jyada precise hoti hai, phase unbalance/loss jald pakadti hai aur digital hoti hai
B. Ye direct short circuit clear kar deti hai
C. Ise power supply ki zarurat nahi
D. Ye sasti padti hai
✓ Sahi Jawab: A
Electronic relays CT ka use karke digital calculations karti hain. Ye phase symmetry, locked rotor, aur earth fault jaise khatarnak faults ko aaram se pakad leti hain jo normal heater bimetal relay nahi kar sakti.
Question 44Medium
Agar MCCB ka handle beech me atka hai (ON aur OFF ke centre me), toh iska kya matlab hai?
A. Breaker ON hai par power bacha raha hai
B. Breaker pura kharab ho gaya hai
C. Breaker kisi fault ki wajah se TRIP ho gaya hai
D. Ye manual test mode hai
✓ Sahi Jawab: C
MCCB me handle ka centre me hona yani ‘TRIPPED’ position. Ise wapas ON karne ke liye pehle handle ko poora zor lagakar niche (OFF) karna padta hai reset karne ke liye, phir upar (ON) hota hai.
Question 45Hard
Main ACB me ‘Icw’ rating ka kya matlab hota hai?
A. Continuous Current Withstand
B. Short-time withstand current (Breaker 1 second tak kitna fault current jhel sakta hai bina trip hue)
C. Instantaneous Current Withstand
D. Wiring ki current rating
✓ Sahi Jawab: B
Icw asli selectivity lata hai. Main breaker jaanboojh kar 1 second tak wait karta hai aur high fault current ko bardasht karta hai (taaki aage wala chota breaker pehle trip ho jaye). Tab tak wo mechanical/thermal damage se bacha rehta hai.
Question 46Medium
Kya RCCB bina kisi Earth wire ke connection ke theek se kaam kar sakti hai?
A. Haan, ye Phase aur Neutral me farak dekhti hai, isme earth jodne ka point nahi hota
B. Nahi, earth wire se hi usko power milti hai
C. Nahi, trip hone ke liye earth wire lazim hai
D. Haan, par sirf DC panel me
✓ Sahi Jawab: A
RCCB/ELCB ke terminal par kabhi Earth wire nahi lagti. Ye Live-Neutral me imbalance dhoondhti hai. Halanki, aage machine (load) ki body me earth lagna zaroori hai taaki current leak ho kar wahan se guzar sake aur RCCB ko fault mil jaye.
Question 47Easy
Modern RCCB pe ‘Test Button’ ka standard color ya marking kya hoti hai?
A. Green
B. Black
C. Color kuch bhi ho sakta hai par us par ‘T’ likha hota hai
D. Hamesha Red hota hai
✓ Sahi Jawab: C
Color alag-alag brand pe depend karta hai (jaise ABB me blue ya yellow, Schneider me white) par duniya bhar me uspe ‘T’ (Test) mark zaroor hota hai.
Question 48Hard
Panel board me khali jageh (empty MCB slots) par blanking plates kyu lagani zaroori hain?
A. Sirf dekhne me acha lage isliye
B. Taki busbar niche na gir jaye
C. Future wire lagane ki jagah bachane ke liye
D. IP rating barkarar rakhne aur kisi ki ungli live busbar se touch na ho isliye
✓ Sahi Jawab: D
Khali jagah chhodne se andar chalu line (live busbar) exposed rehti hai. Blanking plates lagana safety rule hai taaki koi finger wahan galti se touch na ho jaye (IP2X Finger-safe requirement).
Question 49Medium
Distribution board me SPN ka full form kya hota hai?
A. Single Phase Network
B. Single Phase & Neutral
C. Standard Panel Node
D. Solid Protected Neutral
✓ Sahi Jawab: B
SPN (Single Phase & Neutral) aamtaur pe 230V ghar walo ke DB hote hain. TPN (Three Phase & Neutral) ka matlab bade 415V distribution board hote hain.
Question 50Easy
Ghar ki normal lighting circuit ke liye kaun se curve type ka MCB KABHI NAHI lagana chahiye?
A. Type D
B. Type B
C. Type C
D. Koi sa bhi chalta hai
✓ Sahi Jawab: A
Type D tab trip hota hai jab current 10-20 guna badh jaye (welding / heavy machine ke time). Ghar ki patli light wiring me itna fault current gaya toh wire jal jayegi par breaker girega hi nahi. Hamesha Type B ya C use karein.
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