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  • (a) Define Power and state its SI unit. (b) A torch bulb is rated 5 V and 500 mA. Calculate its (i) Power (ii) Resistances (iii) Energy consumed when it is lighted for 2½ hours.

(a) Define Power and state its SI unit.
(b) A torch bulb is rated 5 V and 500 mA. Calculate its

  1. (i) Power
  2. (ii) Resistances
  3. (iii) Energy consumed when it is lighted for 2½ hours.

 

 

 

 
 
 
 
 

Answers (1)

(a)  Rate of doing work or transferring energy per unit time is called power. SI unit of power is Watt which is equal to 1 Joule per second.


(b) 

(i) Power

P = V × A

=5V×0.5A=2.5=5V×0.5A=2.5 W

(ii) Resistance

 R = VIVI

=50.5=10=50.5=10 Ω

(iii) Energy consumed when it is lighted for 2½ hours

power consumed in 1 sec = 2.5 W

So, power consumed in2.5 hours

=2.5×60×60×2.5=225=2.5×60×60×2.5=225 Wh

= 0.225 kWh

Posted by

Safeer PP

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