(1)改装前,两盏路灯每晚需要消耗电能W=Pt=0.025kw×2×10h=0.5kw·h;
(2)每盏灯泡的电阻R=
=
=484Ω;
改装后每个灯泡的功率是P实=
=25W;
故改装后与改装前亮度一样.
(3)D.