Electric current in circuit

Electric current consumers are once lamp with resistance of 200ohm and then lamp with resistance of 500ohm. In both cases power consumed by the lamps is 200W and the wires used to connect the lamps to current source are the same.
What is the current in the wires in case of short circuit?

Call emf of supply 'E' and internal resistance of supply 'r'

With 200Ω
P = I²R
200 = I² x 200
I = 1A
E = I(r + R) so
E = r + 200 (equation 1)

With 500Ω
P = I²R
200 = I² x 500
I = 0.632A
E = I(r + R) so
E = 0.632(r + 500) (equation 2)

From equations 1 and 2
0.632(r + 500) = r + 200
0.368r = 116
r = 315Ω
From equation 1, E = 315 +200 = 515V

Short circuit current = E/r = 515/315 = 1.63A

For help with internal resistance see link.