The current in the original circuit is 1.2 A. after an 8.2 ohm resistor is connected in the circuit, the current becomes 0.5 A, and the resistance and power supply voltage in the original circuit are calculated

Let the resistance in the original circuit be R1 and the supply voltage be u
I1 = u / R1 = 1.2 (a). (1)
If a 8.2 ohm resistor is connected in series in the circuit, the circuit resistance is R2 = R1 + 8.2 (Ohm)
I2 = u / r2 = u / (R1 + 8.2) = 0.5 (a). (2)
From (1), u = 1.2r1. (3)
Substituting (3) into (2), 0.7r1 = 4.1, R1 = 41 / 7 ≈ 5.86 (Euro)
Substituting R1 = 5.86 Ω into (3), u ≈ 7.03 (V)
A: slightly

A 484 ohm resistance wire is connected to a 220 V circuit, and the heat it emits is calculated after 240 seconds of power on

Because heat = power (P) * time (T), known t = 240s, P = IU = u * U / R, known r = 484 ohm, u = 220 V, so p = u * U / r = 220 * 220 / 484 = 100W, so q = Pt = 100 * 240 = 24000j

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