1
JEE Main 2022 (Online) 25th June Morning Shift
+4
-1

A long straight wire with a circular cross-section having radius R, is carrying a steady current I. The current I is uniformly distributed across this cross-section. Then the variation of magnetic field due to current I with distance r (r < R) from its centre will be :

A
B $$\propto$$ r2
B
B $$\propto$$ r
C
B $$\propto$$ $${1 \over {{r^2}}}$$
D
B $$\propto$$ $${1 \over {{r}}}$$
2
JEE Main 2022 (Online) 24th June Evening Shift
+4
-1

The soft-iron is a suitable material for making an electromagnet. This is because soft-iron has

A
low coercivity and high retentivity.
B
low coercivity and low permeability.
C
high permeability and low retentivity.
D
high permeability and high retentivity.
3
JEE Main 2022 (Online) 24th June Evening Shift
+4
-1

A proton, a deutron and an $$\alpha$$-particle with same kinetic energy enter into a uniform magnetic field at right angle to magnetic field. The ratio of the radii of their respective circular paths is :

A
1 : $$\sqrt 2$$ : $$\sqrt 2$$
B
1 : 1 : $$\sqrt 2$$
C
$$\sqrt 2$$ : 1 : 1
D
1 : $$\sqrt 2$$ : 1
4
JEE Main 2022 (Online) 24th June Evening Shift
+4
-1

An electric bulb is rated as 200 W. What will be the peak magnetic field at 4 m distance produced by the radiations coming from this bulb? Consider this bulb as a point source with 3.5% efficiency.

A
1.19 $$\times$$ 10$$-$$8T
B
1.71 $$\times$$ 10$$-$$8T
C
0.84 $$\times$$ 10$$-$$8T
D
3.36 $$\times$$ 10$$-$$8T
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