WBJEE · Physics · Current Electricity
Four cells, each of emf \(E\) and internal resistance \(r,\) are connected in series across an external resistance \(R .\) By mistake one of the cells is connected in reverse. Then the current in the external circuit is
- A \(\frac{2 E}{4 r+R}\)
- B \(\frac{3 E}{4 r+R}\)
- C \(\frac{3 E}{3 r+R}\)
- D \(\frac{2 E}{3 r+R}\)
Answer & Solution
Correct Answer
(A) \(\frac{2 E}{4 r+R}\)
Step-by-step Solution
Detailed explanation
Total emf of the cell \(=3 E-E=2 E\) Total internal resistance \(=4 r\) \(\therefore\) Total resistance of the circuit \(=4 r+R\) So, the current in the external circuit \(\left(\because i=\frac{V}{B}\right)\) \(\therefore\) \[ i=\frac{2 E}{4 r+R} \]
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Physics
- A diver at a depth of \(12 \mathrm{~m}\) in water \(\left(\mu=\frac{4}{3}\right)\) sees the sky in a cone of semivertical angle :WBJEE 2011 Easy
- Two charges \(+q\) and \(-q\) are placed at points \(A\) and \(B\) respectively which are at a distance \(2 L\) apart. \(C\) is the mid point of \(A\) and \(B\). The workdone in moving a charge \(+Q\) along the semicircle \(\operatorname{CSD}\left(W_1\right)\) and along the line \(\operatorname{CBD}\left(W_2\right)\) are
WBJEE 2025 Medium - Consider two concentric spherical metal shells of radii \(r_{1}\) and \(r_{2}\left(r_{2}>r_{1}\right)\). If the outer shell has a charge \(q\) and the inner one is grounded, the charge on the inner shell isWBJEE 2014 Easy
- Two soap bubbles of radii \(\mathrm{x}\) and \(\mathrm{y}\) coalesee to constitute a bubble of radius \(\mathrm{z}\). Then \(\mathrm{z}\) is requal toWBJEE 2011 Medium
- An electron enters an electric field having
intensity \(\mathbf{E}=3 \overrightarrow{\mathbf{i}}+6 \hat{\mathbf{j}}+2 \hat{\mathbf{k}} \cdot \mathbf{V} \mathbf{m}^{-1}\) and magnetic
field having induction \(\mathrm{B}=2 \hat{\mathbf{i}}+3 \hat{\mathbf{j}}\) T with a velocity \(\mathbf{v}=2 \hat{\mathbf{i}}+3 \hat{\mathbf{j}}\) ms \(^{-1}\). The magnitude of the force acting on the electron is (Given, \(\left.e=-1.6 \times 10^{-19} \mathrm{C}\right)\)WBJEE 2016 Hard - A positive charge \(Q\) is situated at the centre of a cube. The electric flux through any face of the cube is (in SI units)WBJEE 2017 Easy
More PYQs from WBJEE
- The solutions set of inequation \(\cos ^{-1} x < \sin ^{-1} x\) isWBJEE 2011 Easy
- \(\int_0^{2 \pi} \theta \sin ^6 \theta \cos \theta d \theta\) is equal toWBJEE 2023 Medium
- If \(\int e^{\sin x} \cdot\left[\frac{x \cos ^{3} x-\sin x}{\cos ^{2} x}\right] d x=e^{\sin x} f(x)+c\)
where c is constant of integration, then \(f(x)\) is
equal toWBJEE 2018 Medium - Let \(f: N \rightarrow R\) be such that \(f(1)=1\) and \(f(1)+2 f(2)+3 f(3)+\ldots+n f(n)=n(n+1) f(n),\) for all \(n \in N, n \geq 2,\) where \(N\) is the set of natural numbers and \(R\) is the set of real numbers. Then, the value of \(f(500)\) isWBJEE 2015 Hard
- In a slide caliper, \((m+1)\) number of vernier divisions is equal to \(m\) number of smallest main scale divisions. If \(d\) unit is the magnitude of the smallest main scale division, then the magnitude of the vernicr constant isWBJEE 2012 Medium
- In a GP series consisting of positive terms, each term is equal to the sum of next two terms. Then, the common ratio of this GP series isWBJEE 2017 Easy