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As shown in the figure on the right, R1 = 30 ohm, R2 = 10 ohm. After closing the switch, the indication of ammeter A is 2a to calculate the power supply voltage!
Answer: 24 V
Analysis:
It is treated as a parallel circuit, because there is no diagram:
In parallel circuit, the main current is equal to the sum of branch currents,
That is: U / R1 + U / r2 = 2
Algebra: U / 30 + U / 20 = 2
Solution: u = 24 V
As shown in the figure, R1 = 30 Ω, R2 = 10 Ω, after closing the switch, the ammeter shows 0.2A
(1) Power supply voltage U = i1r1 = 0.2A × 30 Ω = 6V; (2) current through R2 I2 = UR2 = 6v10 Ω = 0.6A; then the total current is I total = I1 + I2 = 0.2A + 0.6A = 0.8A
As shown in the figure, in the circuit, R1 = 5, when the switch S is closed, I = 0.6A, I1 = 0.4A, calculate the resistance value of R2
Close look at the topic: two resistors in parallel. The voltage is equal, the total current = the sum of branch current
U=U1=I1R1=0.4*5=2v
I2=I-I1=0.6-0.4=0.2A
R2 = u / I2 = 2 / 0.2 = 10 Ω
R1 = 10 ohm, R2 = 20 ohm. After closing the switch, the indication of the ammeter is 0.3A; (1) what is the voltage at both ends of resistance R1? (2) what is the current through R2
Parallel (1) U1 = i1r1 = 0.3A * 10 Ω = 3V (2) I2 = U2 / r2 = 3V / 20 Ω = 0.15A
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