Question

A torch bulb is rated at 3 V and 600 mA. Calculate it’s

1. power
2. resistance
3. energy consumed if it is used for 4 hours.

Answer 1

1. V = 3V and I = 600 mA = 600 × 10^-3 A
   (a) Power (P) = VI
   = 3 × 600 × 10^-3
   = 1800 × 10^-3
   = 1.8 W (or) watt.
2.  Resistance (R) =
   \(\frac{\mathrm{V}}{\mathrm{I}}\) = \(\frac{3}{600 \times 10^{-3}}\) = 5 Ω.
3. Power (P) = 1.8 W and
   Time = 4 hours = 4 × 60 × 60 = 14400 second
   Energy consumed E = P × t = 1.8 × 14400 = 25920 joules
   E = 25.9 KJ.