JEE Mains · Physics · STD 12 - 3. current electricity
A cell, shunted by a \(8 \; \Omega\) resistance, is balanced across a potentiometer wire of length \(3 \; m\). The balancing length is \(2 \; m\) when the cell is shunted by \(4 \; \Omega\) resistance. The value of internal resistance of the cell will be \(\dots \; \Omega .\)
- A \(7\)
- B \(8\)
- C \(9\)
- D \(10\)
Answer & Solution
Correct Answer
(B) \(8\)
Step-by-step Solution
Detailed explanation
\(\frac{V_{1}}{V_{2}}=\frac{3}{2}=\frac{E-i_{1} r}{E-i_{2} r}\) \(=\frac{E-\frac{E}{8+r} \times r}{E-\frac{E}{4+r} \times r}\) \(\frac{3}{2}=\frac{8(4+r)}{4(8+r)}\) \(24+3 r=16+4 r\) \(r=8 \; \Omega\)
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 2 A current carrying straight metal wire of resistance \(1 \Omega\), resistivity \(2 \times 10^{-6} \Omega m\), area of cross-section \(10 mm^2\) and mass 500 g is suspended horizontally in mid air by applying a uniform magnetic field \(\vec{B}\). The magnitude of \(B\) is _______ \(\times 10^{-1} T\) (given, \(g =10 m / s ^2\) ).JEE Mains 2024 Medium
- An atom absorbs a photon of wavelength \(500\,nm\) and emits another photon of wavelength \(600\,nm\). The net energy absorbed by the atom in this process is \(n \times 10^{-4}\,eV\). The value of \(n\) is ............ [Assume the atom to be stationary during the absorption and emission process] \(\left(\right.\)Take \(h =6.6 \times 10^{-34}\,Js\) and \(\left.c =3 \times 10^8\,m / s \right)\)JEE Mains 2023 Medium
- A player caught a cricket ball of mass \(150 \mathrm{~g}\) moving at a speed of \(20 \mathrm{~m} / \mathrm{s}\). If the catching process is completed in \(0.1 \mathrm{~s}\), the magnitude of force exerted by the ball on the hand of the player is _______.JEE Mains 2024 Hard
- A wire \(A\), bent in the shape of an arc of a circle, carrying a current of \(2\, A\) and having radius \(2\, cm\) and another wire \(B ,\) also bent in the shape of arc of a circle, carrying a current of \(3\, A\) and having radius of \(4\, cm ,\) are placed as shown in the figure. The ratio of the magnetic fields due to the wires \(A\) and \(B\) at the common centre \(O\) is
JEE Mains 2020 Hard - A sinusoidal wave of wavelength 7.5 cm travels a distance of 1.2 cm along the x -direction in 0.3 sec. The crest \(P\) is at \(x=0\) at \(t=0 \mathrm{sec}\) and maximum displacement of the wave is 2 cm. Which equation correctly represents this wave ?JEE Mains 2025 Easy
- A torque meter is calibrated to reference standards of mass, length and time each with \(5 \%\) accuracy. After calibration, the measured torque with this torque meter will have net accuracy of\(............\%\)JEE Mains 2022 Medium
More PYQs from JEE Mains
- If \(\int \frac{\cos x-\sin x}{\sqrt{8-\sin 2 x}} d x=a \sin ^{-1}\left(\frac{\sin x+\cos x}{b}\right)+c\) where \(c\) is a constant of integration, then the ordered pair \(( a , b )\) is equal toJEE Mains 2021 Hard
- The number of solutions of the equation \(\cos \left(x+\frac{\pi}{3}\right) \cos \left(\frac{\pi}{3}-x\right)=\frac{1}{4} \cos ^{2} 2 x, x \in[-3 \pi\) \(3 \pi]\) isJEE Mains 2022 Hard
- Let \(S=\{\theta \in[0,2 \pi): \tan (\pi \cos \theta)+\tan (\pi \sin \theta)=0\}\). Then \(\sum_{\theta \in S } \sin ^2\left(\theta+\frac{\pi}{4}\right)\) is equal toJEE Mains 2023 Hard
- The charge stored by the capacitor C in the given circuit in the steady state is _________ \(\mu C\).
JEE Mains 2026 Medium - A fish rising vertically upward with a uniform velocity of \(8\,ms ^{-1}\), observes that a bird is diving vertically downward towards the fish with the velocity of \(12\,ms ^{-1}\). If the refractive index of water is \(\frac{4}{3}\), then the actual velocity of the diving bird to pick the fish, will be \(.......\,ms ^{-1}\).JEE Mains 2023 Medium
- A uniform cable of mass \(‘M’\) and length \(‘L’\) is placed on a horizontal surface such that its \({\left( {\frac{1}{n}} \right)^{th}}\) part is hanging below the edge of the surface. To lift the hanging part of the cable upto the surface, the work done should beJEE Mains 2019 Hard