The magnitude of any physical quantity: A. depends on the method of measurement B. does not depend on the method of measurement C. is more in SI system than in CGS system D. Directly proportional to the fundamental unit of mass, length and time
Hint: We know that physical quantities are the characteristic of any given material. We also know that they are broadly classified into scalars and vectors. The physical quantity is generally written as a numerical with a suitable unit.
Complete answer: To identify the correct answer let us begin by understanding the given options and eliminating the wrong answers: A. depends on the method of measurement According to this difference in method must give a different answer or different magnitude, but this cannot be true. Let us consider the example of finding the distance from A to C via B. Let us assume that the measurements are taken in kilometres. If A to B takes 5km, and B to C takes 2km, we can say that A to C takes 7km. This value of A to C doesn’t vary if we find AB and BC, then add them, or straight away measure AC directly. Thus clearly this option is wrong. B.does not depend on the method of measurement Since option A and B are opposite to each other, we can say that since A is wrong, clearly B is right. Also we saw above that the method of measurement doesn’t affect the magnitude of the quantity. C. is more in SI system than in CGS system This is again wrong as SI units and CGS units are interconvertible and hence one can not be greater than the other. D. Directly proportional to the fundamental unit of mass, length and time This is again not true as there are other fundamental units like ampere. And not just mass, length and time.
Thus the option is B. does not depend on the method of measurement.
Note: Since a physical quantity can either be a scalar with a numerical or a vector with the numerical and direction, we can say that either way any physical quantity has a numerical value. This numerical value is called the magnitude and it can be measured using appropriate scales.