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There is an electric lamp, which consumes 100 watts when connected to the power supply. Connect it in series with another resistor and then connect it to the same power supply. The power consumed by the resistor is 9 watts. The strategy of bulb consumption at this time is proposed
P=U*U/R=100 U*U=100R R=U*U/100
[U/(R+r)]^2*r=9
100R*r/(R+r)^2=9
The solution is: r = 9R r = R / 9
So the power consumed on the bulb is 81 watts or 1 watt
Connect a bulb directly to the power supply, the power is 100 watts, connect the bulb in series with a long wire to the same power supply, the power is 81 watts, then the power loss on the long wire is ()
A. 19 watts B. 10 watts C. 9 watts D. cannot be calculated
Because U1 & nbsp; 2p1 = U2 & nbsp; 2P2, u1u2 = p1p2 = 100w81w = 109, that is, the voltage at both ends of the bulb and the long wire in series is 910 of the power supply voltage, and the voltage at both ends of the long wire is 110 of the power supply voltage. If the power consumed by the long wire is P0, then 91 = 81wp0, and P0 = 9W
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