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CBSE

Subject

Physics

NEET Physics : Moving Charges And Magnetism

Multiple Choice Questions

81.

The ratio of magnetic fields on the axis of a circular current carrying coil of radius a to the magnetic field at its centre will be

$\frac{1}{{(1 + \frac{x^{2}}{a^{2}})}^{\frac{3}{2}}}$
$\frac{1}{{(1 + \frac{a^{2}}{x^{2}})}^{\frac{1}{2}}}$
$\frac{1}{{(1 + \frac{a^{2}}{x^{2}})}^{2}}$
$\frac{1}{{(1 + \frac{a^{2}}{x^{2}})}^{3}}$

82.

In the following diagram, which particle has highest e/m value?

83.

The intensity of magnetic field due to an isolated pole of strength m_p at a point distant r from it will be

m_p/r²
m_p r²
r²/ m_p
m_p/r

84.

When a positively charged particle enters into a uniform magnetic field with uniform velocity, its trajectory can be

(i) a straight line (ii) a circle (iii) a helix

(i) only
(i) or (ii)
(i) or (iii)
any one of (i), (ii) and (iii)

85.

Assertion: Magnetic force between two short magnets, when they are co-axial follows inverse square law of distance.

Reason: The magnetic forces between two poles do not follow inverse square law of distance.

If both assertion and reason are true and reaon is correct explanation of assertion.
If both assertion and reason are true and reaon is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

86.

Assertion: Magnetic field lines are continuous and closed.

Reason: Magnetic monopole does not exist.

If both assertion and reason are true but reason is not the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.

87.

Assertion: If a proton and an a-particle enter a uniform magnetic field perpendicularly with the same speed, the time period of revolution of a particle is double that of proton.

Reason: In a magnetic field, the period of revolution of a charged particle is directly proportional to the mass of the particle and is inversely proportional to charge of particle.

If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.

88.

Assertion: When a radius of circular loop carrying current is doubled, its magnetic moment becomes four times.

Reason: Magnetic moment depends on area of the loop.

If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false

89.

What is the magnetic field at a distance R from a coil of radius r carrying current ?

$\frac{μ_{0} I R^{2}}{2 {(R^{2} + r^{2})}^{\frac{3}{2}}}$
$\frac{μ_{0} I R^{2}}{2 {(R^{2} + r^{2})}^{\frac{3}{2}}}$
$\frac{μ_{0} I}{2 r}$
$\frac{μ_{0} I}{2 R}$

90.

A moving coil galvanometer has a resistance of 900 Ω. In order to send only 10 % of the main current through this galvanometer, the resistance of the required shunt is

0.9 Ω
100 Ω
405 Ω
90 Ω

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