JEE Mains · Physics · STD 12 - 3. current electricity
A \(220 \; V , 50 \; Hz\) AC source is connected to a \(25 \; V\), \(5 \; W\) lamp and an additional resistance \(R\) in series (as shown in figure) to run the lamp at its peak brightness, then the value of \(R\) (in ohm) will be
- A \(975\)
- B \(875\)
- C \(775\)
- D \(675\)
Answer & Solution
Correct Answer
(A) \(975\)
Step-by-step Solution
Detailed explanation
\(P = Vi\) \(5=25 i\) \(i=\frac{1}{5}\) \(V_{R}=i R\) \((220-25)=\frac{1}{5} R\) \(R=195 \times 5=975 \Omega\)
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
- Which of the following are true for a single slit diffraction?
(A) Width of central maxima increases with increase in wavelength keeping slit width constant.
(B) Width of central maxima increases with decrease in wavelength keeping slit width constant.
(C) Width of central maxima increases with decrease in slit width at constant wavelength.
(D) Width of central maxima increases with increase in slit width at constant wavelength.
(E) Brightness of central maxima increases for decrease in wavelength at constant slit width.JEE Mains 2026 Easy - The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2 m away from it, is :JEE Mains 2025 Medium
- Given below are two statements: one is labelled a Assertion \((A)\) and the other is labelled as Reason\((R)\) \(Assertion\) \((A)\) : Work done by electric field on moving a positive charge on an equipotential surface is always zero. \(Reason\) \((R)\) : Electric lines of forces are always perpendicular to equipotential surfaces. In the light of the above statements, choose the most appropriate answer from the options given belowJEE Mains 2024 Hard
- Electrons are accelerated through a potential difference \(V\) and protons are accelerated through a potential difference \(4\, V\). The de-Broglie wavelengths are \(\lambda_e \) and \(\lambda_p \) for electrons and protons respectively. The ratio of \(\frac{{{\lambda _e}}}{{{\lambda _p}}}\) is given by : (given \(m_e\) is mass of electron and \(m_p\) is mass of proton).JEE Mains 2013 Hard
- A parallel plate capacitor has capacitance C , when there is vacuum within the parallel plates.
A sheet having thickness \(\left(\frac{1}{3}\right)^{ rd }\) of the separation between the plates and relative permittivity K is introduced between the plates. The new capacitance of the system is :JEE Mains 2026 Medium - Match List-\(I\) with List-\(II\) :-
Choose the correct answer from the options given below:List - \(I\) (EM-Wave) List - \(II\) (Wavelength) (Range) \((A)\) infra-red \((i)\) \(<10^{-3} \mathrm{~nm}\) \((B)\) Ultraviolet \((ii)\) \(400 \mathrm{~nm}\) to \(1 \mathrm{~nm}\) \((C)\) X-rays \((iii)\) \(1 \mathrm{~mm}\) to \(700 \mathrm{~nm}\) \((D)\) Gamma rays \((iv)\) \(1 \mathrm{~nm}\) to \(10^{-3} \mathrm{~nm}\) JEE Mains 2024 Hard
More PYQs from JEE Mains
- The number of distinct real roots of \(x ^{4}-4 x +1=0\) isJEE Mains 2022 Medium
- Let the six numbers \(a_1, a_2, a_3, a_4, a_5, a_6\) be in \(A.P.\) and \(a_1+a_3=10\). If the mean of these six numbers is \(\frac{19}{2}\) and their variance is \(\sigma^2\), then \(8 \sigma^2\) is equal toJEE Mains 2023 Hard
- The electric field and magnetic field components of an electromagnetic wave going through vacuum is described by \(E _{ x }= E _0 \sin ( kz -\omega t )\) \(B _{ y }= B _0 \sin ( kz -\omega t )\) Then the correct relation between \(E_0\) and \(B_0\) is given byJEE Mains 2023 Medium
- Let \(\vec{a}=\hat{i}+\hat{j}+2 \hat{k}, \vec{b}=2 \hat{i}-3 \hat{j}+\hat{k}\) and \(\overrightarrow{ c }=\hat{ i }-\hat{ j }+\hat{ k }\) be three given vectors. Let \(\vec{v}\) be a vector in the plane of \(\vec{a}\) and \(\overrightarrow{ b }\) whose projection on \(\overrightarrow{ c }\) is \(\frac{2}{\sqrt{3}}\). If \(\overrightarrow{ v } . \hat{ j }=7\), then \(\overrightarrow{ v } \cdot(\hat{ i }+\hat{ k })\) is equal toJEE Mains 2022 Medium
- If the center and radius of the circle \(\left|\frac{z-2}{z-3}\right|=2\) are respectively \((\alpha, \beta)\) and \(\gamma\), then \(3(\alpha+\beta+\gamma)\) is equal toJEE Mains 2023 Hard
- A perpendicular is drawn from a point on the line \(\frac{{x - 1}}{2} = \frac{{y + 1}}{{ - 1}} = \frac{z}{1}\) to the plane \(x + y + z = 3\) such that the foot of the perpendicular \(Q\) also lies on the plane \(x -y + z = 3.\) Then the co-ordinates of \(Q\) areJEE Mains 2019 Hard