灯L1标有“6V,2W”,灯L2标有“12V,2W”,将L1和L2串联后接入某电源上,L2恰能正常发光,求电源电压和L1的实际功率?
问题描述:
灯L1标有“6V,2W”,灯L2标有“12V,2W”,将L1和L2串联后接入某电源上,L2恰能正常发光,求电源电压和L1的实际功率?
答
∵P=U2R,∴两灯的电阻分别为:R1=U21P1=(6V)22W=18Ω;R2=U22P2=(12V)22W72Ω因为串联,L2正常发光,则I1=I2=U2R2=12V72Ω=16A则L1两端的实际电压为:U′1=R1I1=18Ω×16A=3V电源电压为:U=U′1+U2=3V+12V=15VL1的...