Physical Quantities and Measurement Test - 7

K not is a measure of the speed of ship. The term knot dates from the 17th century, when sailors measured the speed of their ship by using a device called a "common log".

Hence, option A is correct.

We know that 1 mm = 0.039 inch

So, 65 mm = 65 mm × 0.039/1mm= 2.6 inches

The Gauss (G), is the cgs unit of measurement of magnetic flux density (B). One gauss is defined as one maxwell per square centimeter.

Thus option A is correct.

In C.G.S system, Maxwell is the unit of magnetic flux

1Wb (S.Iunit) = 10⁸maxwell

Thus option C is correct.

Because Calorie, Joule and Kelvin are related to Heat.

But, Ampere or amp (symbol: A) is the unit of electrical current. The Ampere unit is named after Andre-Marie Ampere, from France. One Ampere is defined as the current that flows with electric charge of one Coulomb per second.

Thus option C is correct.

We know that,

1kg=1000g

1m=100cm

Now, converting the unit kg m² s² into g m² s²

1 kg m² s² = 1000 g × (100 m)²s²kg

=1000×10⁴ g m² s²

=10⁷g cm² s²

Thus option A is correct.

The gradient of any physical quantity is computed to as per unit length. This means it is a rate with respect to length. So, the Displacement gradient will also be length per unit length. Because a displacement gradient is the ratio of two quantities having dimensions of "length". That is, a displacement gradient has units of a meter per meter for example.

The length dimensions will be cancelled, and we have a unitless quantity. While others will be having certain units. Hence it is a unitless quantity.

Thus option B is correct.

Relative density is the ratio of density of one substance to the density of water. So, relative density is a dimensionless quantity which remains the same even if the units of mass, length and time are changed.

Thus option B is correct.

Heat a form of Energy and SI unit of Energy is Joule.

Calorie is also unit of heat energy but it is not SI unit.

\(1 \mathrm{cal}=4.2 \mathrm{J}\)

Calorie is defined as the amount of heat energy needed to raise the temperature of one gram of pure water by one degree Celsius. 1 Kilocalorie are 1000 calories, the amount of caloric energy needed to raise the mass of 1 kg of pure water by 1⁰C. 1 kilocalorie is 4200 Joules.

Thus option C is correct.

The kilowatt hour is a unit of energy equal to \(3.6 \times 10^{6} \mathrm{J}\). If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt hours is the power in kilowatts multiplied by the time in hours. so if \(\mathrm{kWh}\) is unit of energy so none of the option is correct hence option \(D\) is the answer.

SI unit of potential energy is Joule (J).The gravitational potential energy has the same units as kinetic energy, kg m² / s². In fact, all energy has the same units, kg m² / s², and is measured using the SI unit is Joule (J).

Thus option C is correct.

SI unit of magnetic field is  Weber/m². Other units of magnetic field are Tesla and Gauss.

Also,  1 Tesla = 104 Gauss

Thus option B is correct.

Heat Energy  = I²Rt

So, R = J/A²s = Kgm²s⁻³A−2

Electric potential is defined as the work done to move a unit positive charge from one point to another point.

The SI unit of electric potential is volt(V).

Hence, \(V=\frac{J}{C}\)

Hence, \(V=\frac{J}{C}=J C^{-1}\)