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Multiple choice properties of magnet magnetism physics neutral points magnetic poles and magnetic compass magnetic field

A device used by the sailors to find the direction in which their ship is moving is called .................

  1. horse shoe

  2. curve

  3. magnetic field

  4. magnetic needle
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A device used by the sailors to find the direction in which their ship is moving is called magnetic needle.
A compass contains a magnetic needle pivoted in a horizontal plane that indicates the direction of magnetic north at points on the earth's surface. It is an instrument containing a freely suspended magnetic element which displays the direction of the horizontal component of the Earth's magnetic field at the point of observation.
It is the oldest instrument for navigation and has been a vital tool for navigators at sea for centuries.

Multiple choice properties of magnet magnetism physics neutral points magnetic poles and magnetic compass magnetic field

Two parallel conductors are separated by 5cm. They carry 6A and 2A in the same direction. Between them the location from first at which magnetic needle lies along $B _H$ is

  1. 1.25 cm

  2. 3.75 cm

  3. 2.5 cm

  4. no point exist
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Two parallel conductors carrying currents I1 = 6A and I2 = 2A in the same direction. The magnetic field at distance x from the first conductor is B = (μ0/4π)(2I1/x - 2I2/(d-x)), where d = 5cm. For the magnetic needle to lie along Earth's horizontal field Bh, the net magnetic field must be zero (balanced by Bh). Setting B = 0 gives I1/x = I2/(d-x), so 6/x = 2/(5-x). Cross-multiplying: 6(5-x) = 2x, so 30 - 6x = 2x, giving 30 = 8x, so x = 30/8 = 3.75 cm from the first conductor.

Multiple choice properties of magnet magnetism physics neutral points magnetic poles and magnetic compass magnetic field

A magnetic needle oscillates in a horizontal plane with a period $T$ at a place where the angle of dip is $60^0$. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be 

  1. $\frac{T}{\sqrt 2}$

  2. T

  3. 2T

  4. 6T
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a horizontal plane, the period is T = 2 * pi * sqrt(I / (M * BH)). In a vertical plane, the effective field is the total magnetic field B = BH / cos(delta), where delta is the angle of dip. Thus, T_v = 2 * pi * sqrt(I / (M * B)) = T * sqrt(cos(delta)). With delta = 60 degrees, cos(60) = 1/2, so T_v = T / sqrt(2).

Multiple choice properties of magnet magnetism physics neutral points magnetic poles and magnetic compass magnetic field

When a current of $1$ ampere is passed in a coil lying in the magnetic meridian then a magnetic needle at its centre gives some deflection. If the current in the coil is increased to $\sqrt8$ ampere then at what distance from the centre of the coil will the deflection of needle remains underchanged?

  1. $2R$
  2. $4R$
  3. $8R$
  4. $R$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice physics light, shadows and images introduction to reflection of light light and sight images in plane mirror

For a total internal reflection, which of the following is correct?

  1. Light travel from rarer to denser medium.

  2. Light travel from denser to rarer medium.

  3. Light travels in air only.

  4. Light travels in water only.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The total internal reflection occurs when the ray of light is reflected totally into the same medium even without the presence of a mirror. The total internal reflection occurs when a ray of light travels from denser medium to rarer medium.