Magnetic Field | MCQs

Explanation

A magnetic compass is a device that responds to the presence of a magnetic field by aligning its needle with the direction of the field.

It is a common tool used to detect and measure magnetic fields.

Explanation

Magnetic poles always exist in pairs, with every magnet having a north pole and a south pole.

Like poles (north-north or south-south) repel each other.

Unlike poles (north-south or south-north) attract each other.

Explanation

Explanation

• One parallel to the field (causes straight motion)
• One perpendicular to the field (causes circular motion)

Explanation

Formula:

B=μ0​I/2πr​

Where:

• $mu_0 = 4pi times 10^{-7} , text{T·m/A}$ 

• $I = 5 , text{A}$ (current)

• $r = 2,text{cm} = 0.02,text{m}$

Substituting Values:

$$B = frac{4pi times 10^{-7} , text{T·m/A} times 5 , text{A}}{2 times 3.14 times 0.02, text{m}}$$2×3.14×0.02m​

Let’s calculate step by step:

Numerator:

$$4pi times 10^{-7} times 5 = 20pi times 10^{-7}$$

Denominator:

$$2 times 3.14 times 0.02 = 0.1256$$

Now,

$$B = frac{20pi times 10^{-7}}{0.1256}$$0.1256​

$$approx frac{62.8 times 10^{-7}}{0.1256} approx 5 times 10^{-5} , text{T}$$0.1256 ≈5×10^−5T

Explanation

The force on a moving charge in a uniform magnetic field depends on:

• Magnetic flux density (B): The strength of the magnetic field.
• The charge on the particle (q): The amount of charge on the particle.
• The speed of the particle (v): The velocity at which the particle is moving.

The force (F) on a moving charge in a uniform magnetic field is given by the Lorentz force equation: F = q (v x B)

Where x denotes the cross product.

Explanation

The force exerted on a charged particle by a magnetic field is perpendicular to both the magnetic field and the velocity of the particle. This is described by the Lorentz force equation: F = q (E + v x B)

Where:

• F is the force
• q is the charge
• E is the electric field
• v is the velocity
• B is the magnetic field
• x denotes the cross product

The cross product of two vectors results in a vector that is perpendicular to both of the original vectors.

Therefore, the force due to the magnetic field and velocity is at right angles to each other.

Explanation

When magnets are used in magnetic therapy, the poles are often referred to as being positive or negative.

Explanation

• Electromagnets require an electric current to generate a magnetic field.
• Whereas bar magnets are permanent magnets that do not require electricity to exhibit magnetism.
• This is the main difference between the two types of magnets.

Explanation

• When two same poles (north-north or south-south) of magnets are brought close to each other, they repel each other.
• This is because like poles have the same polarity and therefore push each other away.