P7

   Dt = 0.1 s,   I = 1 mA = 10**-3 A,

   Dq = I Dt = 10**-3 x 0.1 = 10**-4 C

   N = Dq / e = 10**-4 / 1.6 x 10**-19 = 6.2 x 10**14  protons

P37

  

I x 3R = V R = V/3I = 300 / 3 x 4 = 25 Ohm V (across each resistor) = 300V / 3 = 100V

P67

    Power P = IV = 180A x 12V = 2.2 KW

    Energy W = PDt = 2.2 KW x 2s = 4.4 KJ