Ask anything
electrical.
506 straight answers — in English and Hindi, searched as you type, Hinglish welcome. Calculators for the questions that need numbers, and live circuits to play with.
- 506 answers
- 20 topics
- 11 in-depth guides
- 6 calculators
- 2 live circuits
- हिंदी में भी
The bench
Calculators for the questions that need numbers.
Wire and MCB for any load, a month's bill, the right fan and geyser, voltage drop on long runs, and every unit conversion an electrician needs.
Current8.7 Aat 230 V, power factor 0.8
MCB16 AC-curve
Copper wire2.5 sq mmcarries ≈ 21 A at 40 °C
Voltage drop over 15 m0.9%within 5%
Every circuit needs an MCB no bigger than its wire can carry, an earth, and a 30 mA RCCB in the board. Motors and ACs draw a surge at start: C-curve MCBs ride through it.
Reference ratings: PVC copper in conduit, two loaded conductors (IEC 60364-5-52, B1), ×0.87 for 40 °C. Fewer amps if several circuits share a conduit. General guidance — follow IS 732 and your electrician.
The lab
Switch it, short it, trip it.
Two circuits every home has, to operate rather than read about: a staircase light, and the breakers that keep a house safe.
Circuit 01
The staircase light
Two two-way switches joined by two ‘traveller’ wires. Whichever switch you flip, the light changes — the current only reaches the lamp when both switches pick the same traveller.
Light off
Circuit 02
MCB and RCCB, doing their jobs
A 16 A C-curve MCB protects the wire; a 30 mA RCCB protects people. Push the load, short it, or leak current to earth.
RCCB · 30 mA
MCB · C16
9.0A
0mA leaking
All normal: current flows out on the phase and back on the neutral.
Every answer, by topic
506 answers in 20 topics.
Answer first, then the same in Hindi, with the Indian standard where there is one and the Samaksh range it's about.
Lighting
- 30LED lighting basicsLED लाइट की बुनियादी बातें
- What is an LED light?
- Should I compare LED lights by watts or by lumens?
- How many lumens does a 9 W LED bulb give?
- 27Panels, downlights & spotsपैनल, डाउनलाइट और स्पॉट
- What size hole (cut-out) does a recessed LED panel need?
- What's the difference between recessed and surface LED panels?
- How far apart should downlights be?
- 24Strip, rope & profile lightsस्ट्रिप, रोप और प्रोफ़ाइल लाइट
- What's the difference between 12 V, 24 V and 230 V LED strips?
- Where can I cut an LED strip?
- What size driver do I need for an LED strip?
- 25Outdoor, street & solar lightsबाहर, गली और सोलर लाइट
- What IP rating do outdoor lights need?
- What does IP65 actually mean?
- What wattage flood light do I need?
- 20Bulbs, battens & holdersबल्ब, बैटन और होल्डर
- What's the difference between B22 and E27 bulbs?
- What is an emergency (inverter) LED bulb?
- Should I replace old tube lights with LED battens?
Switches, protection & safety
- 30Switches & socketsस्विच और सॉकेट
- What's the difference between modular and non-modular switches?
- What's the difference between 6 A and 16 A switches and sockets?
- What is a two-way (staircase) switch?
- 31MCBs, RCCBs & the MCB boxMCB, RCCB और DB
- What does an MCB protect against?
- What do B, C and D curves on an MCB mean?
- Which MCB rating should I use for lights, sockets, AC and geyser?
- 28Earthing & shock safetyअर्थिंग और करंट से सुरक्षा
- What is earthing, and why does a house need it?
- What are the types of earthing for a house?
- What earth resistance should I aim for?
- 19Plugs & extension boardsप्लग और एक्सटेंशन बोर्ड
- How much load can an extension board take?
- What's the difference between a spike guard and a plain extension board?
- Can I plug one extension board into another?
Wires, pipes & backup
- 30Wires & cablesतार और केबल
- Which wire size is used for what in house wiring?
- Which wire size do I need for a 1.5 ton AC?
- How much current can 1.5, 2.5 and 4 sq mm wire carry?
- 21Conduit, pipes & boxesकंड्यूट, पाइप और बॉक्स
- Which size conduit pipe is used in house wiring?
- What are light, medium and heavy gauge conduits?
- How many wires can go in one conduit?
- 21Inverters, backup & solarइनवर्टर, बैकअप और सोलर
- What size inverter (VA) do I need?
- What size battery do I need for my inverter?
- What's the difference between flat-plate, tubular and lithium inverter batteries?
Fans & appliances
- 30Ceiling, table & exhaust fansसीलिंग, टेबल और एग्ज़ॉस्ट पंखे
- What size ceiling fan do I need for my room?
- How high should a ceiling fan be from the floor?
- What's the difference between BLDC and ordinary ceiling fans?
- 25Geysers & water heatersगीज़र और वॉटर हीटर
- What size geyser do I need?
- What's the difference between instant and storage water heaters?
- How long does a geyser take to heat water?
- 26Heaters, irons & kitchenहीटर, प्रेस और किचन
- Which room heater is best for a bedroom?
- What wattage room heater do I need?
- How much electricity does a room heater use?
Planning, bills & fixing
- 26Bills & saving energyबिल और बिजली की बचत
- What is one 'unit' of electricity?
- How do I calculate how many units an appliance uses?
- Which appliances use the most electricity at home?
- 28Planning a home's wiringघर की वायरिंग की योजना
- How do I plan the electrical layout of a new house?
- How many circuits does a house need?
- What electrical points does a bedroom need?
- 31Troubleshootingखराबी और समाधान
- Power is off in only part of my house. Why?
- My whole house has no power but the neighbours do. What now?
- My voltage is very low and lights are dim. What can I do?
- 14Numbers & formulasनंबर और फ़ॉर्मूले
- How do I convert watts to amps at 230 V?
- How many watts is 1 HP?
- What does '1 ton' mean for an air conditioner?
- 20For electricians & shopsइलेक्ट्रीशियन और दुकानदार
- What does the ISI mark on an electrical product mean?
- What is a BIS registration (R-) number?
- How can I spot counterfeit electrical goods?
In depth
11 guides, with tables and the standards behind them.
Lighting
- How many lumens or LED lights do I need for my room?Light homes to roughly 100–200 lux in bedrooms and living rooms, 200–300 lux in kitchens (up to 500 lux on the worktop) and 300–500 lux for study and office areas. To size the lights: lumens needed ≈ target lux × floor area in m² ÷ 0.5. A 12 × 12 ft bedroom (13.4 m²) at 150 lux needs about 4,000 lumens from its fittings.6 min
- Should I use warm white or cool white LED lights at home?Use warm white (2700–3000K) for bedrooms, living and dining rooms; neutral white (around 4000K) for kitchens, bathrooms, study rooms, offices and shops; and cool white or daylight (5700–6500K) for utility areas, warehouses and outdoor security lighting. Keep one colour temperature within a room so it looks consistent.4 min
- What is the difference between COB and SMD LED lights?A COB (chip-on-board) LED packs many LED chips into one small light-emitting surface, giving a single, focused beam with one clean shadow — ideal for downlights, spotlights and accent lighting. SMD (surface-mounted device) LEDs are individual packages spread across a board, giving wide, even light — ideal for bulbs, panels, battens and strip lights.3 min
- What is the difference between B22 and E27 bulbs?B22 is a 22 mm bayonet cap with two side pins that you push in and twist — it's the standard holder in most Indian homes. E27 is a 27 mm Edison screw cap, common in decorative fittings and imported lamps. They are not interchangeable without an adapter, so check your holder before buying.2 min
- What IP rating do I need for outdoor or bathroom lights?An IP (Ingress Protection) rating has two digits: the first is protection against solids and dust (0–6), the second against water (0–9). Use IP20 indoors, IP44 or higher in bathrooms and covered balconies, IP65 or higher for lights exposed to rain such as flood lights, gate lights and street lights, and IP66–IP67 where there are strong water jets or temporary flooding.4 min
Switchgear
- What is the difference between an MCB and an RCCB?An MCB (miniature circuit breaker) protects wiring from overload and short circuit. An RCCB (residual current circuit breaker) protects people from electric shock and reduces fire risk by tripping when current leaks to earth — typically at 30 mA — but it does not protect against overload or short circuit. An RCBO does both in one device. Most homes need an RCCB plus an MCB on every circuit.7 min
- Should I use modular or non-modular switches?Modular switches clip into a plate mounted on a concealed box, so you can mix switches, sockets, regulators and USB modules and replace any one later — they're the standard for new homes and offices. Non-modular (conventional or piano-type) switches mount on a switchboard sheet and cost less, which suits budget rewiring and utility areas.4 min
Wiring
- Which size wire should I use for lights, sockets, AC and geyser?In Indian homes, 1.5 sq mm copper wire is typically used for lights and fans, 2.5 sq mm for general sockets, 4 sq mm for heavy loads such as air conditioners and water heaters, and 6–10 sq mm for the main supply depending on the total connected load. Use multi-strand copper with FR or FR-LSH insulation, and size every circuit with its MCB following IS 732.7 min
- Which PVC conduit pipe should I use for house wiring?Use medium-gauge (MMS) rigid PVC conduit for most concealed wiring in walls, heavy-gauge (HMS) inside concrete slabs and floors or wherever it could be crushed, and light gauge only for low-risk surface runs. 20 mm conduit suits switchboard drops and lighting circuits; 25 mm suits main runs and circuits with more wires. Don't fill a conduit beyond about 40% of its internal area.4 min
Glossary
35 electrical terms in one line each.