Question

What is the voltage drop across the entire parallel portion of the circuit?

Answer 1

Given:

The value of each of the parallel resistances is,

`60\text{ ohm}`

The resistance in series with it is,

`30\text{ ohm}`

The potential difference across the combination is,

`V=120\text{ V}`

To find:

The potential drop across the parallel portion

Step-by-step explanation:

The circuit diagram looks like:

The equivalent resistance of the circuit is,

`\begin{gathered} R=30.0+(60.0\parallel60.0) \\ =30.0+(60.0*60.0)/(60.0+60.0) \\ =30.0+30.0 \\ =60.0\text{ ohm} \end{gathered}`

The current through the circuit is,

`\begin{gathered} i=(V)/(R) \\ =(120)/(60.0) \\ =2.0\text{ A} \end{gathered}`

The potential drop across 30.0 ohm is,

`\begin{gathered} V_(30.0)=i*30.0 \\ =2.0*30.0 \\ =60\text{ V} \end{gathered}`

The potential drop across the rest parallel portion is,

`\begin{gathered} V_(rest)=V-V_(30.0) \\ =120-60 \\ =60\text{ V} \end{gathered}`

Hence, the voltage drop across the entire parallel portion is 60 V.