Two lamps, one rated 100w;220v , and the other 60w;220v, are connected in parallel to electric mains supply. Find the current drawn by two bulbs from the line, if the supply voltage is 220v.
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Answer
- Current will be 0.72 A
Explanation
Given
In case 1
- Power = 100W
- Voltage = 220V
In case 2
- Power = 60W
- Voltage = 220V
To Find
- The current drawn
Solution
We shall first find the resistance and then use the current using the Ohm's law
In case 1
→ P = V²/R
→ 100 = 220²/R
→ R = 220²/100
→ R = 48400/100
→ R = 484Ω
In case 2
→ P = V²/R
→ 60 = 220²/R
→ R = 220²/60
→ R = 48400/60
→ R = 806.7Ω
✭ Net resistance
→ 1/R = 1/R¹ + 1/R².....
→ 1/R = {1/484}+{1/806.7}
→ R = 302.5Ω
✭ Current drawn
→ V = IR
→ 220 = I×302.5
→ 220/302.5 = I
→ I = 0.72 A
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