1
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

A wire of resistance R is bent into an equilateral triangle and an identical wire is bent into $a$ square. The ratio of resistance between the two end points of an edge of the triangle to that of the square is

A
$8 / 9$
B
$9 / 8$
C
$32 / 27$
D
$27 / 32$
2
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Consider a long thin conducting wire carrying a uniform current I. A particle having mass "M" and charge " $q$ " is released at a distance " $a$ " from the wire with a speed $v_0$ along the direction of current in the wire. The particle gets attracted to the wire due to magnetic force. The particle turns round when it is at distance $x$ from the wire. The value of $x$ is [ $\mu_0$ is vacuum permeability]

A
$a\left[1-\frac{m v_o}{2 q \mu_0 \mathrm{I}}\right]$
B
$a e^{-\frac{4 \pi \mathrm{mv}_o}{q \mu_o \mathrm{I}}}$
C
$a\left[1-\frac{\mathrm{mv}}{\mathrm{q}} \mu_{\mathrm{o}} \mathrm{I}\right]$
D
$\frac{a}{2}$
3
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Due to presence of an em-wave whose electric component is given by $E=100 \sin (\omega t-k x) \mathrm{NC}^{-1}$ a cylinder of length 200 cm holds certain amount of em-energy inside it. If another cylinder of same length but half diameter than previous one holds same amount of em-energy, the magnitude of the electric field of the corresponding em-wave should be modified as

A
$50 \sin (\omega \mathrm{t}-\mathrm{kx}) \mathrm{NC}^{-1}$
B
$400 \sin (\omega \mathrm{t}-\mathrm{kx}) \mathrm{NC}^{-1}$
C
$200 \sin (\omega t-k x) \mathrm{NC}^{-1}$
D
$25 \sin (\omega \mathrm{t}-\mathrm{kx}) \mathrm{NC}^{-1}$
4
JEE Main 2025 (Online) 28th January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

Three infinitely long wires with linear charge density $\lambda$ are placed along the $x-a x i s, y-a x i s$ and $z-$ axis respectively. Which of the following denotes an equipotential surface?

A
$\left(x^2+y^2\right)\left(y^2+z^2\right)\left(z^2+x^2\right)=$ constant
B
$x y z=$ constant
C
$x y+y z+z x=$ constant
D
$(x+y)(y+z)(z+x)=$ constant
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