The electric lamp emits 900 kJ of heat in 2.5 hours of operation. Determine the power of the lamp
March 22, 2021 | education
| The electric lamp emits 900 kJ of heat in 2.5 hours of operation. Determine the power of the lamp and the amperage in it if the voltage is 200 V.
t = 2.5 h = 9000 s.
Q = 900 kJ = 900000 J.
U = 200 V.
N -?
I -?
According to the Joule-Lenz law, the amount of heat Q that is released in a conductor through which an electric current flows is determined by the formula: Q = I ^ 2 * U * t. Where I is the current in the conductor, U is the voltage at the ends of the conductor, t is the current flow time.
I = √ (Q / U * t).
I = √ (900000 J / 200 V * 9000 s) = 0.7 A.
The power of the lamp N, through which the electric current flows, is determined by the formula: N = I * U.
N = 0.7 A * 200 V = 140 W.
Answer: lamp power N = 140 W, current I = 0.7 A.
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