The potential difference across $ 8 $ ohm resistance is $ 48 $ volt as shown in the figure. The value of potential difference across X and Y points will be
(A) $ 128 $ volt
(B) $ 160 $ volt
(C) $ 80 $ volt
(D) $ 62 $ volt
Answer
638.7k+ views
Hint : To solve this question, we need to assume a battery between the points X and Y of emf equal to the unknown potential difference. Then we have to simplify the circuit by calculating the parallel equivalent resistance.
Complete step by step answer
Let the potential difference across X and Y points be $ V $ . So let us consider a battery of emf $ V $ connected across the points X and Y as shown in the figure below.
According to the question, the potential difference across the $ 8 $ ohm resistance is equal to $ 48 $ volt. So referring to the above figure, the potential difference between the points A and B is $ 48 $ volt. According to the polarity of the battery, the point B should be at a higher potential than the point A. So we have
$\Rightarrow {V_{BA}} = 8{\text{V}} $ ……………………….(1)
Now, the $ 24\Omega $ and $ 8\Omega $ resistances are in parallel combination across the point A and B. So the equivalent resistance between the points A and B, $ {R_{AB}} $ is given by
$\Rightarrow \dfrac{1}{{{R_{AB}}}} = \dfrac{1}{8} + \dfrac{1}{{24}} $
On solving we get
$\Rightarrow {R_{AB}} = 6\Omega $
Also, across the points B and C, the $ 20\Omega ,30\Omega ,60\Omega $ resistances are arranged in parallel combination. So the equivalent resistance across the points B and C is given by
$\Rightarrow \dfrac{1}{{{R_{BC}}}} = \dfrac{1}{{20}} + \dfrac{1}{{30}} + \dfrac{1}{{60}} $
On solving we get
$\Rightarrow {R_{BC}} = 10\Omega $
So the above circuit can be redrawn as
Now, let $ I $ be the current in the circuit. From Ohm’s law we have
$\Rightarrow V = IR $ ..........................(2)
Now, the equivalent resistance in the circuit is given by
$\Rightarrow R = 3\Omega + 10\Omega + 6\Omega + 1\Omega $
$ \Rightarrow R = 20\Omega $
So from (2) we have
$\Rightarrow V = 20I $
$ \Rightarrow I = \dfrac{V}{{20}} $ ........................(3)
The potential difference across the points A and B is equal to that across the $ 6\Omega $ resistance. Therefore we have
$\Rightarrow {V_{BA}} = 6I $
From (3)
$\Rightarrow {V_{BA}} = \dfrac{{6V}}{{20}} $ ........................(4)
Equating (1) and (4) we have
$\Rightarrow \dfrac{{6V}}{{20}} = 48 $
$ \Rightarrow V = 160{\text{V}} $
Thus, the potential difference between the points X and Y is equal to $ 160 $ volts.
Hence, the correct answer is option B.
Note
The points X and Y are not shown to be connected through any battery in the figure given in the question. But the potential difference which is given across the $ 8 $ ohm resistance clearly indicates that a voltage source must be present there. Hence we were able to assume the battery between X and Y.
Complete step by step answer
Let the potential difference across X and Y points be $ V $ . So let us consider a battery of emf $ V $ connected across the points X and Y as shown in the figure below.
According to the question, the potential difference across the $ 8 $ ohm resistance is equal to $ 48 $ volt. So referring to the above figure, the potential difference between the points A and B is $ 48 $ volt. According to the polarity of the battery, the point B should be at a higher potential than the point A. So we have
$\Rightarrow {V_{BA}} = 8{\text{V}} $ ……………………….(1)
Now, the $ 24\Omega $ and $ 8\Omega $ resistances are in parallel combination across the point A and B. So the equivalent resistance between the points A and B, $ {R_{AB}} $ is given by
$\Rightarrow \dfrac{1}{{{R_{AB}}}} = \dfrac{1}{8} + \dfrac{1}{{24}} $
On solving we get
$\Rightarrow {R_{AB}} = 6\Omega $
Also, across the points B and C, the $ 20\Omega ,30\Omega ,60\Omega $ resistances are arranged in parallel combination. So the equivalent resistance across the points B and C is given by
$\Rightarrow \dfrac{1}{{{R_{BC}}}} = \dfrac{1}{{20}} + \dfrac{1}{{30}} + \dfrac{1}{{60}} $
On solving we get
$\Rightarrow {R_{BC}} = 10\Omega $
So the above circuit can be redrawn as
Now, let $ I $ be the current in the circuit. From Ohm’s law we have
$\Rightarrow V = IR $ ..........................(2)
Now, the equivalent resistance in the circuit is given by
$\Rightarrow R = 3\Omega + 10\Omega + 6\Omega + 1\Omega $
$ \Rightarrow R = 20\Omega $
So from (2) we have
$\Rightarrow V = 20I $
$ \Rightarrow I = \dfrac{V}{{20}} $ ........................(3)
The potential difference across the points A and B is equal to that across the $ 6\Omega $ resistance. Therefore we have
$\Rightarrow {V_{BA}} = 6I $
From (3)
$\Rightarrow {V_{BA}} = \dfrac{{6V}}{{20}} $ ........................(4)
Equating (1) and (4) we have
$\Rightarrow \dfrac{{6V}}{{20}} = 48 $
$ \Rightarrow V = 160{\text{V}} $
Thus, the potential difference between the points X and Y is equal to $ 160 $ volts.
Hence, the correct answer is option B.
Note
The points X and Y are not shown to be connected through any battery in the figure given in the question. But the potential difference which is given across the $ 8 $ ohm resistance clearly indicates that a voltage source must be present there. Hence we were able to assume the battery between X and Y.
Recently Updated Pages
What is BLO What is the full form of BLO class 8 social science CBSE

Explain the Treaty of Vienna of 1815 class 10 social science CBSE

10 examples of friction in our daily life

Draw a diagram of nephron and explain its structur class 11 biology CBSE

Write structures of the following compounds i 2 Chloro3methylpentane class 11 chemistry CBSE

A Paragraph on Pollution in about 100-150 Words

Trending doubts
Draw a labelled sketch of the human eye class 12 physics CBSE

Which are the Top 10 Largest Countries of the World?

Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE

Draw ray diagrams each showing i myopic eye and ii class 12 physics CBSE

Which is the correct genotypic ratio of mendel dihybrid class 12 biology CBSE

What is the Full Form of PVC, PET, HDPE, LDPE, PP and PS ?

