1
JEE Main 2022 (Online) 26th July Evening Shift
+4
-1

Two concentric circular loops of radii $$r_{1}=30 \mathrm{~cm}$$ and $$r_{2}=50 \mathrm{~cm}$$ are placed in $$\mathrm{X}-\mathrm{Y}$$ plane as shown in the figure. A current $$I=7 \mathrm{~A}$$ is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately :

A
$$\frac{7}{2} \hat{k} \,\mathrm{Am}^{2}$$
B
$$-\frac{7}{2} \hat{k} \,\mathrm{Am}^{2}$$
C
$${7}\, \hat{k} \,\mathrm{Am}^{2}$$
D
$${-7}\, \hat{k} \,\mathrm{Am}^{2}$$
2
JEE Main 2022 (Online) 26th July Evening Shift
+4
-1

A velocity selector consists of electric field $$\vec{E}=E \,\hat{k}$$ and magnetic field $$\vec{B}=B \,\hat{j}$$ with $$B=12 \,m T$$. The value of $$E$$ required for an electron of energy $$728 \,\mathrm{e} V$$ moving along the positive $$x$$-axis to pass undeflected is :

(Given, mass of electron $$=9.1 \times 10^{-31} \mathrm{~kg}$$ )

A
$$192 \,\mathrm{kVm}^{-1}$$
B
$$192 \,\mathrm{mVm}^{-1}$$
C
$$9600 \,\mathrm{kVm}^{-1}$$
D
$$16 \,\mathrm{kVm}^{-1}$$
3
JEE Main 2022 (Online) 26th July Morning Shift
+4
-1

A charge particle is moving in a uniform magnetic field $$(2 \hat{i}+3 \hat{j}) \,\mathrm{T}$$. If it has an acceleration of $$(\alpha \hat{i}-4 \hat{j})\, \mathrm{m} / \mathrm{s}^{2}$$, then the value of $$\alpha$$ will be :

A
3
B
6
C
12
D
2
4
JEE Main 2022 (Online) 26th July Morning Shift
+4
-1

$$\mathrm{B}_{X}$$ and $$\mathrm{B}_{\mathrm{Y}}$$ are the magnetic fields at the centre of two coils $$\mathrm{X}$$ and $$\mathrm{Y}$$ respectively each carrying equal current. If coil $$X$$ has 200 turns and $$20 \mathrm{~cm}$$ radius and coil $$Y$$ has 400 turns and $$20 \mathrm{~cm}$$ radius, the ratio of $$B_{X}$$ and $$B_{Y}$$ is :

A
1 : 1
B
1 : 2
C
2 : 1
D
4 : 1
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