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NEETPhysicsCurrent Electricity

A student in a town in India, where the price per unit (1 unit = 1 kWh ) of electricity is ₹ 5 . 00 , purchases a 1 kVA UPS (uninterrupted power supply) battery. A day before the exam, 10 friends arrive to the student's home with their laptops and all connect their laptops to the UPS. Assume that each laptop has a constant power requirement of 90 W . Consider the following statements. I. All the 10 laptops can be pow

Options

  1. AI only
  2. BI and II only
  3. CI and III only
  4. DII and III only .

Correct answer

C. I and III only

Step-by-step solution

Power requirement for 1 laptop, P 1 = 90 W So, power r quirement for 10 laptops, P = 10 × P 1 = 10 × 90 - 900 W = 0 . 9 kW In 5 h , electrical energy used by all laptops, E = P × t = 0 . 9 × 5 = 4 . 5 kWh cost of electrical energy used is cost = E × Unit cost = 4 . 5 × 5 = ₹ 22 . 50 So, statement III is correct. For laptop charger, input voltage is 220 V So, current when all 10 laptops are connected through an extension, I = P V = 900 220 ≈ 4 . 1 A As, line current exceeds current rating of fuse, therefore 3 A fuse

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