An electric lamp is included in the circuit with a voltage of 220V. When the rheostat was switched on in series

| June 17, 2021 | education

An electric lamp is included in the circuit with a voltage of 220V. When the rheostat was switched on in series, the current strength changed from 0.5 to 0.2 A. Draw a circuit diagram and find the resistance of the rheostat

Let the resistance of the lamp be R1 and the resistance of the rheostat equal to R2.

Determine the resistance of the lamp in the circuit when the resistance of the rheostat is zero and the current is 0.5 A.

U = I1 * (R1 + R2) = I1 * R1.

R1 = U / I1 = 220 / 0.5 = 440 Om.

Determine the resistance of the circuit when the rheostat and the lamp are turned on, and the current in the circuit is 0.2 A.

U = I2 * (R1 + R2).

220 = 0.2 * (440 + R2).

0.2 * R2 = 220 – 0.2 * 440 = 132.

R2 = 132 / 0.2 = 660 Om.

Answer: The resistance of the rheostat is 660 ohms.



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