   Question Answers

# In the given electric circuit, the current flowing through the 3ohm resistor is 1ampere. Find the voltage of the battery and the circuit drawn from it.   Hint: In a parallel combination of resistors, the current divides but voltage between the terminals is the same and reciprocal of the total resistance is the sum of the reciprocal of individual resistances.
In series combination of resistors voltage divides between two resistors but same current flows through them and effective resistance is the sum of the two resistances.

Consider circuit diagram, where ${{R}_{1}}=2\Omega ,{{R}_{2}}=3\Omega$ and ${{R}_{3}}=6\Omega$. Let ${{I}_{2}}=1A$ is the current flowing through ${{R}_{2}}$ as given in the question. Now we have to find I and V which are total current and potential respectively.
Now first part to find total current I, we have,
$I={{I}_{1}}+{{I}_{2}}$ …….. (1)
we already know ${{I}_{2}}$ as it is given in question we have to find ${{I}_{1}}$
To find ${{I}_{1}}$ :
$I{}_{1}=\dfrac{{{V}_{2}}}{{{R}_{3}}}$ ….. (2)
the same voltage ${{V}_{2}}$ flows through ${{R}_{3}}$ as they are aligned parallel to each other.
but we don’t know ${{V}_{2}}$, it can be determined by using the formula:
${{V}_{2}}={{I}_{2}}{{R}_{2}}$ (Ohm’s law)
on substituting values of resistance and current we get,
${{V}_{2}}=1\times 3=3V$
On substituting ${{V}_{2}}$ in (2) we get
\begin{align} & {{I}_{1}}=\dfrac{{{V}_{2}}}{{{R}_{3}}}=\dfrac{3}{6} \\ & {{I}_{1}}=\dfrac{1}{2}A=0.5A \\ \end{align}
Now we know both ${{I}_{1}}$and${{I}_{2}}$ substituting in (1) we get
\begin{align} & I=1+0.5 \\ & I=1.5A \\ \end{align}
Thus, total current flowing through the circuit is found.
Now second part to find total potential V, we have,
$V={{V}_{1}}+{{V}_{2}}$ …… (3)
We know what is ${{V}_{2}}$ but have to find ${{V}_{1}}$ ,
${{V}_{1}}=I{{R}_{1}}$
on substituting I and ${{R}_{1}}$ we get
\begin{align} & {{V}_{1}}=1.5\times 2 \\ & {{V}_{1}}=3V \\ \end{align}
on substituting values in (3)
\begin{align} & V=3+3 \\ & V=6V \\ \end{align}
Thus, total potential of the circuit is found.

Note: Students should remember all the above formulas to solve this type of question.
Students may get confused about V and I which is constant, and which will vary when connected in series and parallel. Always remember that in series combination of resistors voltage divides current remains same between resistors and in parallel combination, the current divides but voltage remains constant.
View Notes
Electric Current in Conductors  Electric Current and Its Effects  Chemical Effects of Electric Current  Magnetic Effects of Electric Current  Integrated Circuit  Electric Car  Electric Power  CBSE Class 12 Physics Electric Charges and Fields Formula  Electric Potential - Point Charge  Electric Charge and Static Electricity  CBSE Class 8 Science Chemical Effects of Electric Current Worksheets  CBSE Class 7 Science Electric Current and Its Effects Worksheets  Important Questions for CBSE Class 12 Physics Chapter 1 - Electric Charges and Fields  Important Questions for CBSE Class 12 Physics Chapter 3 - Current Electricity  Important Questions for CBSE Class 8 Science Chapter 14 - Chemical Effects of Electric Current  Important Questions for CBSE Class 12 Physics Chapter 7 - Alternating Current  Important Questions for CBSE Class 7 Science Chapter 14 - Electric Current and Its Effects  Important Questions for CBSE Class 10 Science Chapter 13 - Magnetic Effects of Electric Current  NCERT Books Free Download for Class 12 Physics Chapter 1 - Electric Charges and Fields  Important Questions for CBSE Class 6 Social Science The Earth Our Habitat Chapter 1 - The Earth In The Solar System  CBSE Class 12 Physics Question Paper 2020  Previous Year Question Paper for CBSE Class 12 Physics  Previous Year Question Paper for CBSE Class 12 Physics - 2015  Previous Year Question Paper for CBSE Class 12 Physics - 2018  Previous Year Question Paper for CBSE Class 12 Physics - 2014  Previous Year Question Paper for CBSE Class 12 Physics - 2013  Previous Year Question Paper for CBSE Class 12 Physics - 2019  Previous Year Physics Question Paper for CBSE Class 12 - 2017  Physics Question Paper for CBSE Class 12 - 2016 Set 1 C  Previous Year Question Paper for CBSE Class 12 Physics - 2016 Set 1 S  HC Verma Class 12 Physics Part-2 Solutions for Chapter 32 - Electric Current in Conductors  NCERT Solutions for Class 10 Science Chapter 13  Electric Current and Its Effects NCERT Solutions - Class 7 Science  Chemical Effects of Electric Current NCERT Solutions - Class 8 Science  NCERT Solutions for Class 12 Physics Chapter 1  Lakhmir Singh Physics Class 10 Solutions Chapter 2 - Magnetic Effects of Electric Current  HC Verma Class 12 Physics Part-2 Solutions for Chapter 29 - Electric Field and Potential  NCERT Solutions for Class 12 Physics Chapter 1 Electric Charges and Fields In Hindi  NCERT Solutions for Class 12 Physics Chapter 7  NCERT Solutions for Class 12 Physics Chapter 3  