Resistances 80352

We connect a 9V battery, 2 light bulbs in parallel, and a switch to the circuit. When the switch is turned on, a current of 0.5 A passes through the first bulb and a current of 8 A through the unbranched part of the circuit. Draw the connection and calculate the ratio of the branches I1: I2 and the ratio of the resistances of the bulbs.

Correct answer:

r =  1:15
r₂ =  15:1

Step-by-step explanation:

$$\begin{gathered} U=9\text{V} \\ {I}_1=0.5\text{A} \\ I=8\text{A} \\ I=I_1+I_2 \\ {I}_2=I-I_1=8-0.5=\frac{15}{2}=7\frac{1}{2}=7.5\text{A} \\ r=I_1:I_2=0.5:7.5=1:15\approx 0.0667=1:15 \end{gathered}$$

$$\begin{gathered} r_2=R_1:R_2 \\ {r}_2=I_2:I_1=7.5:0.5=15:1=15 \end{gathered}$$

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