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About electric power At present, there is a kind of electric energy meter, which is inserted after the user buys it, and the electric energy meter reads the amount in the card. Once the amount is used up, the electric energy meter will cut off the circuit. It needs to go to the bank to store the value for it, and then insert the electric energy meter again before it can be used. There is also a new type of electric energy meter, in which the electric energy is calculated by the internal electronic circuit, and its count is displayed (Note: the blank should be filled in)
At present, there is a kind of (intelligent) electric energy meter, which is inserted after the user buys (electric card), and the electric energy meter reads the amount in the card. Once the amount is used up, the electric energy meter cuts off the circuit, which needs to go to the bank to store value for it, and then insert the electric energy meter again. There is also a new type of electric energy meter, in which the electric energy is calculated by the internal electronic circuit without rotation (rotor or mechanical part), Its count has (digital) display
Second year physics power exercises, how to do ah, help
A 36V, 100W lamp is connected to the circuit. The current passing through it is 2a, and the actual power is calculated
Lamp resistance R = u ^ 2 / P = 36 ^ 2 / 100 = 12.96 Ω
Actual power = I ^ 2 * r = 2 ^ 2 * 12.96 = 51.84w
A and B lamps are respectively marked with the words "12V 36W" and "24V 18W" and connected in series in the 36V circuit. Then which bulb lights normally and which bulb may burn out? Please explain through calculation
Another question: after the filament in the incandescent bulb is burned out, it is connected to the original power supply again. Does the bulb turn on or dark? Why?
(1) The resistance of a lamp "12V 36W" is r = u ^ 2 / P = 12x12 / 36 = 4 Ω
Rated current I = u / P = 12 / 36 = 1 / 3A
Resistance of B lamp "24 V 18 W" r = u ^ 2 / P = 24 x 24 / 18 = 32 Ω
The total current is I = u / r = 36 / (4 + 32) = 1A when connected in series in a 36V circuit
The total current is greater than the rated current of a lamp, so the "12V 36W" of a lamp may burn out
(2) After lapping, the filament length becomes shorter and the filament resistance becomes smaller
According to P = u ^ 2 / R, the voltage remains unchanged, R becomes smaller, so the actual power P of the bulb becomes larger
And the brightness of the bulb is determined by the actual power. The power becomes larger, so the brightness becomes brighter
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