Easyphysics
WJEC  - GCSE Science
Physics 1 - Energy
Glossary
Formulae

Did you know? 

The power is usually marked on the electric appliance . A kettle marked with 2 kW means it converts 2000 joules of electrical energy into heat in one second.

 

      

 P1 Power 

Syllabus Summary Questions Answers
 
 1) Answers are in table in red. See also the working out below table.
 Appliance Voltage (V) Current (A) Power (W)
 Fridge 230 10 2300
 Radio 12 0.5 6
 Mobile phone 3 0.33 1

 
   Fridge
  Power = voltage x current

  P = V x I

  P = 230 x 10

  P = 2300 W

  
  Radio                                                                    Mobile Phone
 Current = power ÷ voltage

 I = P ÷ V 

 I = 6 ÷ 12   

 I = 0.5 A

      Voltage = power ÷ current

     V = P ÷ I

     V = 1 x 0.33

     V = 3 V
      
 2) A lamp is connected to a 230 V supply and a current of 0.26 flows for 5 minutes. 

     Energy transfer = power x time

     Energy transfer = (230 x 0.26) x (5 x 60)      Time is measured in seconds

     Energy transfer = 17 940 J