Tag: physics

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Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

What is the  $SI$  unit of permeability?

  1. Henry per metre

  2. Tesla metre per ampere

  3. Weber per ampere metre

  4. All the above units are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Permeability (mu) is related to magnetic field intensity H and magnetic flux density B by B = mu*H. The SI unit of B is Tesla (T) and H is Ampere per metre (A/m), so mu = B/H has units of T/(A/m) = T*m/A. Henry per metre (H/m) is also a standard unit, and Weber per ampere metre (Wb/A*m) is equivalent to H/m.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

If E and H represent electric field and magnetic field intensity respectively, then E/H has unit of 

  1. Ampere

  2. Ohm

  3. Volt

  4. Joule
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The ratio of electric field intensity E (V/m) to magnetic field intensity H (A/m) is known as the intrinsic impedance of the medium. The unit is (V/m) / (A/m) = V/A, which is the definition of an Ohm.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

Which of the following is not the unit of surface tension ? 

  1. $newton/meter$

  2. $joule/(meter)^2$

  3. $kg/(second)^2$

  4. $watt/ meter$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Surface tension is force per unit length (N/m). Since N = kg*m/s^2, N/m = kg/s^2. Also, surface tension is energy per unit area (J/m^2). Watt/meter is power per unit length, which is not surface tension.