Question

A torch bulb is rated 2. 5V and 600 mA... calculate its power... it's resistance.. and energy consumed if this bulb is lighted for 4 hours

Answer 1

V=2.5 V
I= 600 mA = 0.6 A
∵ P= V.I
∴P= 2.5 × 0.6 = 1.5 W (power)
 ∵R= $V^{2}$/P
∴R= (2.5×2.5)/1.5= 4.16 Ω (resistance)
∵energy consumed, H=$I^{2}$. R. t
∴H= 0.6 A×0.6 A×4.16 Ω×14400 s                (time, t= 4hr= 4×60×60=14400s)
     =21565.44 J
     =21.56 kJ