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Numbers & formulas
नंबर और फ़ॉर्मूले
Watts to amps, HP, tons, kVA, lumens, voltage drop and cost.
How do I convert watts to amps at 230 V?
Amps = watts ÷ 230 for resistive loads like heaters, irons and geysers: a 2,000 W geyser draws about 8.7 A. For motors and other loads with a power factor below 1, divide by 230 × power factor (a 1,000 W motor at PF 0.8 draws about 5.4 A).
हिंदी एम्पियर = वाट ÷ 230 (हीटर, प्रेस, गीज़र के लिए): 2000 W ≈ 8.7 A। मोटर के लिए वाट ÷ (230 × पावर फ़ैक्टर)।
How many watts is 1 HP?
One horsepower is about 746 W of mechanical output. A 1 HP pump draws more than that from the mains because the motor isn't 100% efficient — often around 900–1,100 W in practice.
हिंदी 1 HP ≈ 746 W (आउटपुट); 1 HP पंप मेन से आम तौर पर 900–1100 W लेता है।
What does '1 ton' mean for an air conditioner?
It's cooling capacity, not weight or power: 1 ton of refrigeration is about 3.5 kW (12,000 BTU per hour) of heat removed. The electricity an AC draws is much less than its cooling capacity — a 1.5 ton unit often draws roughly 1.2–1.8 kW, depending on its efficiency.
हिंदी 1 टन = लगभग 3.5 kW ठंडक (12,000 BTU/घंटा); 1.5 टन AC बिजली आम तौर पर 1.2–1.8 kW लेता है।
What's the difference between kW and kVA?
kW is real power — what does the work and what homes are billed for. kVA is apparent power — voltage × current — which is higher when the power factor is below 1. kW = kVA × power factor; generators, UPSs and inverters are rated in kVA.
हिंदी kW असली पावर है, kVA आभासी (वोल्ट × एम्पियर); kW = kVA × पावर फ़ैक्टर। जनरेटर-इनवर्टर kVA में रेटेड होते हैं।
What is Ohm's law?
Voltage = current × resistance (V = I × R). Power = voltage × current (P = V × I). Together they explain why thin wires heat up: more current through more resistance means more heat (I²R).
हिंदी ओम का नियम: V = I × R; पावर P = V × I। ज़्यादा करंट और प्रतिरोध = ज़्यादा गर्मी (I²R)।
How is three-phase power calculated?
Power (W) = √3 × line voltage × current × power factor. On a 415 V supply, a balanced 10 A per phase at PF 0.9 is about 1.73 × 415 × 10 × 0.9 ≈ 6.5 kW.
हिंदी थ्री-फ़ेज़ पावर = √3 × लाइन वोल्टेज × करंट × पावर फ़ैक्टर; 415 V, 10 A, PF 0.9 ≈ 6.5 kW।
Why is the supply 230 V and 415 V in India?
Indian low-voltage supply is 230 V between a phase and neutral, and 415 V between any two phases of a three-phase supply (230 × √3), at 50 Hz. Homes usually get one phase; larger loads get all three.
हिंदी भारत में फ़ेज़-न्यूट्रल 230 V और दो फ़ेज़ के बीच 415 V (50 Hz) होता है।
What does 50 Hz mean?
Mains electricity in India alternates 50 times a second (50 hertz). Appliances made for 60 Hz countries may run differently here — check the rating plate when buying imported motors and clocks.
हिंदी 50 Hz यानी बिजली एक सेकंड में 50 बार दिशा बदलती है; विदेशी 60 Hz उपकरण की रेटिंग देखें।
How do I convert square feet to square metres?
Divide square feet by 10.76: a 12 × 12 ft room is 144 sq ft ≈ 13.4 m². Lighting and fan guides often use one or the other, so it's useful for working out lux and lumens.
हिंदी वर्ग फ़ुट ÷ 10.76 = वर्ग मीटर; 12×12 फ़ीट = 144 वर्ग फ़ुट ≈ 13.4 वर्ग मीटर।
How do I work out the lumens a room needs?
Lumens ≈ target lux × floor area in m² ÷ 0.5, where 0.5 allows for light lost to walls, ceiling height and fittings. For a 13.4 m² bedroom at 150 lux: 150 × 13.4 ÷ 0.5 ≈ 4,000 lumens.
हिंदी ज़रूरी ल्यूमेन ≈ लक्स × क्षेत्रफल (वर्ग मीटर) ÷ 0.5; 13.4 वर्ग मीटर बेडरूम, 150 लक्स = लगभग 4,000 ल्यूमेन।
How do I convert fan sizes between inches and millimetres?
Multiply inches by 25.4: 36" ≈ 900 mm, 42" ≈ 1050 mm, 48" ≈ 1200 mm and 56" ≈ 1400 mm — the common Indian ceiling-fan sweeps.
हिंदी इंच × 25.4 = मिमी: 36" ≈ 900, 42" ≈ 1050, 48" ≈ 1200 और 56" ≈ 1400 मिमी।
How do I work out what an appliance costs to run?
Cost = watts × hours ÷ 1,000 × your rate per unit. A 1,500 W heater for 3 hours at ₹7 a unit: 1,500 × 3 ÷ 1,000 = 4.5 units × ₹7 ≈ ₹31.5. Use the actual tariff on your bill.
हिंदी खर्च = वाट × घंटे ÷ 1000 × प्रति यूनिट दर; 1500 W हीटर, 3 घंटे, ₹7/यूनिट ≈ ₹31.5।
How much heat energy does it take to warm water?
About 1.16 Wh per litre for each °C of rise. Warming 15 litres by 40 °C takes 15 × 40 × 1.16 ≈ 700 Wh (0.7 units) — before losses.
हिंदी हर लीटर पानी को 1 °C गर्म करने में लगभग 1.16 Wh; 15 लीटर को 40 °C गर्म करने में ≈ 0.7 यूनिट।
How do I calculate voltage drop in a wire?
For a single-phase circuit: drop (V) ≈ 2 × length (m) × current (A) × resistance (Ω per km) ÷ 1,000. Flexible copper is about 13.3 Ω/km for 1.5 sq mm, 7.98 for 2.5, 4.95 for 4 and 3.3 for 6 sq mm. Keep the drop within about 3–5% of 230 V.
हिंदी वोल्टेज ड्रॉप ≈ 2 × लंबाई (मी) × करंट × प्रतिरोध (Ω/किमी) ÷ 1000; 230 V का 3–5% से कम रखें।
General guidance — follow IS 732 and local rules, and use a licensed electrician.
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