N-03-01-001-vr-010 Casio fx-82NL
┘
Eerst de weerstanden parallel
Rv = 1/ [ 1/R1 + 1/R2 ]
Rv = 1 : ( 1 : 2 + 1 : 2 ) = 1 Kohm
Nu twee weerstanden in serie van elk 1 Kohm
Rt = R1 = R2
Rt = 1 + 1 = 2 Kohm
U = I x R
I = U / R
I = 40 / 2K = 20 mA
I = 40 : 2 3 20 -3 = 20 mA