Electromagnetism PYQ — Page 25

For a uniformly charged thin spherical shell, the electric potential $(V)$ radially away from the centre $(O)$ of shell can be graphically represented as 

Three concentric spherical metallic shells $X,Y$ and $Z$ of radius $a,b$ and $c$ respectively $[a<b<c]$ have surface charge densities $\sigma ,–\sigma$ and $\sigma$, respectively. The shells $X$ and $Z$ are at same potential. If the radii of $X&Y$ are $2\mathrm{cm}$ and $3\mathrm{cm}$, respectively. The radius of shell $Z$ is _____$\mathrm{cm}$.

A network of four resistances is connected to $9V$ battery, as shown in figure. The magnitude of voltage difference between the points $A$ and $B$ is __________ $V$. 

In the circuit shown, the energy stored in the capacitor is $n\mu J$. The value of $n$ is _____. 

A long straight wire of circular cross-section (radius $a$) is carrying steady current $I.$ The current $I$ is uniformly distributed across this cross-section. The magnetic field is

The number of turns of the coil of a moving coil galvanometer is increased in order to increase current sensitivity by $50%$. The percentage change in voltage sensitivity of the galvanometer will be :

Electric potential at a point $P$ due to a point charge of $5\times {10}^{-9}C$ is $50V$. The distance of $P$ from the point charge is: (Assume, $\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}N{m}^{2}{C}^{-2}$)

As shown in the figure, two parallel plate capacitors having equal plate area of $200{\mathrm{cm}}^{2}$ are joined in such a way that $a\neq b$. The equivalent capacitance of the combination is $x{\epsilon }_{0}F$. The value of $x$ is _____. 

Which of the following correctly represents the variation of electric potential $(V)$ of a charged spherical conductor of radius $(R)$ with radial distance $(r)$ from the centre?

Two long parallel wires carrying currents $8A$ and $15A$ in opposite directions are placed at a distance of $7\mathrm{cm}$ from each other. A point $P$ is at equidistant from both the wires such that the lines joining the point $P$ to the wires are perpendicular to each other. The magnitude of magnetic field at $P$ is ______ $\times {10}^{-6}T$. (Given: $\sqrt{2}=1.4$)

Match List I with List II <table class="pyq-table"><tbody><tr><td colspan="2" rowspan="1">List – I (Current configuration)</td><td colspan="2" rowspan="1">List – II (Magnetic field at point $O$)</td></tr><tr><td>A</td><td><img src="https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Magnetic_Effects_of_Current/648b5a6f417cc3fb48d68059/question_1__q_648b5a6f417cc3fb48d68059__cdn-question-pool.getmarks.app__6d4d8a8b-2cf2-4134-983a-f4d799603481-30c03559-a817-48e9-903a__ea5c80dc0b_final_ppt_sync.png" alt="JEE Main 2023 Physics, Magnetic Effects of Current — question figure 1"></td><td>I.</td><td>${B}_{0}=\frac{{\mu }_{0}I}{4\pi r}[\pi +2]$</td></tr><tr><td>B</td><td><img src="https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Magnetic_Effects_of_Current/648b5a6f417cc3fb48d68059/question_2__q_648b5a6f417cc3fb48d68059__cdn-question-pool.getmarks.app__fa41edbe-9bec-4bce-b977-38641dda9526-9894246_B__1d8500f970_final_ppt_sync.png" alt="JEE Main 2023 Physics, Magnetic Effects of Current — question figure 2"></td><td>II.</td><td>${B}_{0}=\frac{{\mu }_{0}}{4}\frac{I}{r}$</td></tr><tr><td>C</td><td><img src="https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Magnetic_Effects_of_Current/648b5a6f417cc3fb48d68059/question_3__q_648b5a6f417cc3fb48d68059__cdn-question-pool.getmarks.app__0455c956-7478-44d1-aafb-f6da4de894cc-9894246_C__68b5fd56ef_final_ppt_sync.png" alt="JEE Main 2023 Physics, Magnetic Effects of Current — question figure 3"></td><td>III.</td><td>${B}_{0}=\frac{{\mu }_{0}I}{2\pi r}[\pi -1]$</td></tr><tr><td>D</td><td><img src="https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Magnetic_Effects_of_Current/648b5a6f417cc3fb48d68059/question_4__q_648b5a6f417cc3fb48d68059__cdn-question-pool.getmarks.app__514b245c-d49c-45f0-bee9-5eeea479953f-9894246_D__0d22150df7_final_ppt_sync.png" alt="JEE Main 2023 Physics, Magnetic Effects of Current — question figure 4"></td><td>IV.</td><td>${B}_{0}=\frac{{\mu }_{0}I}{4\pi r}[\pi +1]$</td></tr></tbody></table>Choose the correct answer from the option given below:

A student is provided with a variable voltage source $V$, a test resistor ${R}_{T}=10\Omega$, two identical galvanometers ${G}_{1}$ and ${G}_{2}$ and two additional resistors, ${R}_{1}=10M\Omega$ and ${R}_{2}=0.001\Omega$. For conducting an experiment to verify ohm's law, the most suitable circuit is:

In the given circuit, the equivalent resistance between the terminal A and B is ____ $\Omega$ 

A current carrying circular loop of radius R produces a magnetic field B at its center. At what distance from center on its axis, the magnetic field becomes B/8?

The $H$ amount of thermal energy is developed by a resistor in $10s$ when a current of $4A$ is passed through it. If the current is increased to $16A$, the thermal energy developed by the resistor in $10s$ will be

The energy of an electromagnetic wave contained in a small volume oscillates with

Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R. Assertion A : For measuring the potential difference across a resistance of $600\Omega$, the voltmeter with resistance $1000\Omega$ will be preferred over voltmeter with resistance $4000\Omega$. Reason R : Voltmeter with higher resistance will draw smaller current than voltmeter with lower resistance. In the light of the above statements, choose the most appropriate answer from the options given below

A straight wire AB of mass $40g$ and length $50\mathrm{cm}$ is suspended by a pair of flexible leads in uniform magnetic field of magnitude $0.40T$ as shown in the figure. The magnitude of the current required in the wire to remove the tension in the supporting leads is _____ $A$. (Take $g=10m{s}^{-2})$. 

A $1m$ long metal rod $XY$ completes the circuit as shown in figure. The plane of the circuit is perpendicular to the magnetic field of flux density $0.15T$. If the resistance of the circuit is $5Ω$, the force needed to move the rod in direction, as indicated, with a constant speed of $4m{s}^{-1}$ will be _______${10}^{–3}N$. 

A single turn current loop in the shape of a right angle triangle with sides $5\mathrm{cm},12\mathrm{cm},13\mathrm{cm}$ is carrying a current of $2A$. The loop is in a uniform magnetic field of magnitude $0.75T$ whose direction is parallel to the current in the $13\mathrm{cm}$ side of the loop. The magnitude of the magnetic force on the $5\mathrm{cm}$ side will be $\frac{x}{130}N$. The value of $x$ is _______.

The current sensitivity of moving coil galvanometer is increased by $25%$. This increase is achieved only changing in the number of turns of coils and area of cross section of the wire while keeping the resistance of galvanometer coil constant. The percentage change in the voltage sensitivity will be:

In this figure the resistance of the coil of galvanometer $G$ is $2Ω$. The emf of the cell is $4V$. The ratio of potential difference across ${C}_{1}$ and ${C}_{2}$ is 

The electric field at a distance r from an infinitely long uniformly charged wire having linear charge density λ is:

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : If an electric dipole of dipole moment $30\times {10}^{–5}Cm$ is enclosed by a closed surface, the net flux coming out of the surface will be zero. Reason R : Electric dipole consists of two equal and opposite charges. In the light of above, statements, choose the correct answer from the options given below.