Electric Power

1 (a)     P = VI               P power in W

                                    V p.d. in V       

                                    I current in A

 

 

3000 = 240 x I

I=3000/240 =12.5A

 

(b)      V = IR

240=12.5R

R = 240/12.5 = 19.2 Ω

 

(c)      3 kW = 3000 W = 3000 joules per second

Energy used in 1 min = 3000 x 60 = 180 000 J

 

2        8A       31.25Ω

 

3        Resistance depends upon temperature

 

4        1 641 600 J

 

5        4800J

 

6        6

 

7        2.083 kW

 

8        1920W 1687.5 W

 

9        .64m

 

10      50kW  0.072W