Source And Effects Of Magnetic Field | Physics JEE previous year questions with Solutions

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Topic Question Set

Q 1 :
A 2 A current carrying straight metal wire of resistance 1 $Ω$ , resistivity $2 \times 10^{- 6} Ω m$ , area of cross-section 10 $m m^{2}$ 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/s²) [2024]

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(5) $R = \frac{ρ l}{A} \Rightarrow l = \frac{R A}{ρ} = \frac{1 \times 10 \times 10^{- 6}}{2 \times 10^{- 6}} = 5 m$

$i l B = m g \Rightarrow B = \frac{m g}{i l}$

$B = \frac{(0.5) (10)}{2 \times 5} = 5 \times 10^{- 1} T$

Q 2 :
A charge of 4.0 μC is moving with a velocity of $4.0 \times 10^{6} m s^{- 1}$ along the positive y-axis under a magnetic field $\vec{B}$ of strength ( $2 \hat{k}$ ) T. The force acting on the charge is $x \hat{i}$ N. The value of $x$ is ____. [2024]

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(32) $q = 4 μ C, \vec{v} = 4 \times 10^{6} \hat{j} m / s,$ $\vec{B} = 2 \hat{k} T$

$\vec{F} = q (\vec{v} \times \vec{B}) = 4 \times 10^{- 6} (4 \times 10^{6} \hat{j} \times 2 \hat{k})$

$\vec{F} = 4 \times 10^{- 6} \times 8 \times 10^{6} \hat{i} = 32 \hat{i} N$

$x = 32$

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