JEE Mains · Physics · STD 12 - 3. current electricity
An ideal battery of \(4\, V\) and resistance \(R\) are connected in series in the primary circuit of a potentiometer of length \(1\, m\) and resistance \(5\,\Omega \) . The value of \(R\), to give a difference of \(5\, mV\) across \(10\, cm\) of potentiometer wire, is: ................ \(\Omega\)
- A \(490\)
- B \(480\)
- C \(395\)
- D \(495\)
Answer & Solution
Correct Answer
(C) \(395\)
Step-by-step Solution
Detailed explanation
\(i=\frac{4}{5+R}\) \(V_{A B}=i(5)=\frac{20}{5+R}\) \(V_{A P}=\frac{V_{A B}}{L}(0.1)=\frac{20}{5+R}\left(\frac{0.1}{1}\right)=\frac{2}{5+R}\) Now, \(\frac{2}{5+R}=5 \times 10^{-3}\) \(\Rightarrow \quad R=395\, \Omega\)
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
- There is a small source of light at some depth below the surface of water (refractive index \(=\frac{4}{3}\) ) in a tank of large cross sectional surface area. Neglecting any reflection from the bottom and absorption by water, percentage of light that emerges out of surface is (nearly)...........\(\%\) [Use the fact that surface area of a spherical cap of height \(\mathrm{h}\) and radius of curvature \(\mathrm{r} \text { is } 2 \pi \mathrm{rh}]\)JEE Mains 2020 Hard
- A metallic surface is illuminated with radiation of wavelength \(\lambda\), the stopping potential is \(V_0\). If the same surface is illuminated with radiation of wavelength \(2 \lambda\), the stopping potential becomes \(\frac{V_0}{4}\). The threshold wavelength for this metallic surface will be -JEE Mains 2023 Medium
- Given below are two statements :
Statement (I) : When an object is placed at the centre of curvature of a concave lens, image is formed at the centre of curvature of the lens on the other side.
Statement (II) : Concave lens always forms a virtual and erect image.
In the light of the above statements, choose the correct answer from the options given below :JEE Mains 2024 Medium - A closed and an open organ pipe have same lengths. If the ratio of frequencies of their seventh overtones is \(\left(\frac{a-1}{a}\right)\) then the value of \(a\) is _______.JEE Mains 2024 Medium
- A galvanometer having a coil of resistance \(30 \Omega\) need 20 mA of current for full-scale deflection. If a maximum current of 3 A is to be measured using this galvanometer, the resistance of the shunt to be added to the galvanometer should be \(\frac{30}{X} \Omega\), where \(X\) is ________.JEE Mains 2025 Medium
- Hydrogen atom is bombarded with electrons accelerated through a potential different of \(\mathrm{V}\), which causes excitation of hydrogen atoms. If the experiment is being formed at \(\mathrm{T}=0 \mathrm{~K}\). The minimum potential difference needed to observe any Balmer series lines in the emission spectra will be \(\frac{\alpha}{10} \mathrm{~V}\), where \(\alpha=\) _______.JEE Mains 2024 Hard
More PYQs from JEE Mains
- The ratio of the power of a light source \(S_1\) to that the light source \(S_2\) is \(2 . S_1\) is emitting \(2 \times 10^{15}\) photons per second at 600 nm . If the wavelength of the source \(S_2\) is 300 nm , then the number of photons per second emitted by \(S_2\) is _______ \(\times 10^{14}\).JEE Mains 2025 Medium
- A ray of light coming from the point \(P(1,2)\) gets reflected from the point \(\mathrm{Q}\) on the \(\mathrm{x}\)-axis and then passes through the point \(R(4,3)\). If the point \(S(h\), \(\mathrm{k})\) is such that \(\mathrm{PQRS}\) is a parallelogram, then \(\mathrm{hk}^2\) is equal toJEE Mains 2024 Hard
- Consider \(10\) observation \(\mathrm{x}_1, \mathrm{x}_2, \ldots, \mathrm{x}_{10}\). such that \(\sum_{i=1}^{10}\left(x_i-\alpha\right)=2\) and \(\sum_{i=1}^{10}\left(x_i-\beta\right)^2=40\), where \(\alpha, \beta\) are positive integers. Let the mean and the variance of the observations be \(\frac{6}{5}\) and \(\frac{84}{25}\) respectively. The \(\frac{\beta}{\alpha}\) is equal to :JEE Mains 2024 Hard
- A hollow spherical ball of uniform density rolls up a curved surface with an initial velocity \(3\, m / s\) (as shown in figure). Maximum height with respect to the initial position covered by it will be \(...........cm\).
JEE Mains 2023 Hard - The region represented by \(\{z=x+i y \in C:|z|-\operatorname{Re}(z) \leq 1\}\) is also given by the inequalityJEE Mains 2020 Hard
- The integral \(\int {{{\sec }^{2/3}}\,x\,\cos e{c^{4/3}}} x\,dx\) is equal to : (Here \(C\) is a constant of integration)JEE Mains 2019 Hard