Two lamps are connected in parallel to the network. The resistance of one of the lamps is greater than the other.

| September 11, 2021 | education

Two lamps are connected in parallel to the network. The resistance of one of the lamps is greater than the other. Which lamp will generate more heat in the same time? A) in both lamps the same heat will be released B) in the one where the resistance is greater C) in the one where the resistance is less D) there is no definite answer, since the amount of heat generated does not depend on the resistance of the material

R1> R2.
t1 = t2.
Q1? Q2.
According to the Joule-Lenz law, the amount of heat Q that is released in the conductor is determined by the formula: Q = U * I * t. Where U is the voltage across the conductor, I is the current in the conductor, t is the time the current flows in the conductor.
The amount of heat in the first Q1 lamp is determined by the formula: Q1 = U1 * I1 * t1.
The amount of heat in the second lamp Q2 is determined by the formula: Q2 = U2 * I2 * t2.
For a parallel connection, the following relation is valid: U1 = U2.
I1 = U1 / R1, I2 = U2 / R2.
Q1 = U1 * t1 * U1 / R1 = U1 ^ 2 * t1 / R1.
Q2 = U2 * t2 * U2 / R2 = U2 ^ 2 * t2 / R2.
Since R1> R2, U1 = U2, t1 = t2, then Q1 <Q2.
Answer: the amount of heat will be released more in a lamp in which the resistance is less: at R1> R2 Q1 <Q2.



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