Mechanical Engineering 1. MCQ Practice Tests.

## Units & Measurements MCQ Test - Set 03

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World Famous Personality. Worlds Honours and Awards. World Geography.Physics is a quantitative science, based on measurement of physical quantities. Certain physical quantities have been chosen as fundamental or base quantities. The fundamental quantities that are chosen are Length, Mass, Time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. Each base quantity is defined in terms of a certain basic arbitrarily chosenbut properly standardised reference standard called unit such as metre,kilogram,second,ampere,kelvin,mole,and candela.

The units for the fundamental base quantities are called fundamental or base units and two supplementary units in relation to quantities plane angle and solid angle radian, Ste radian.

Other physical quantities derived from the base quantities can be expressed as a combination of the base units and are called derived units. A complete set of units both fundamental and derived units are called a system of units. Example :- volume, density etc. In computing any physical quantity the units for derived quantities involved in the relationships are treated as though they were algebraic quantities till the desired units are obtained.

In measured quantities while expressing theresult, the accuracy and precision of measuring instrumentsalong with errors in measurement should be taken into account. Dimensional analysis can be used to check the dimensional consistency of equations, deducing relations among physical quantities etc. A dimensionally consistent equation need not be actually an exact equation, but a dimensionally wrong or inconsistent equation must be wrong.

These are the errors that tend to be either positive or negative. Sources of systematic errors are i Instrumental errors ii Imperfection in experimental technique or procedure iii Personal errors. Those errors which occur irregularly. These errors arise due to unpredictable fluctuations in experimental conditions.

The magnitude of the difference between the individual measurement and the true value of the quantity is called the absolute error of the measurement. The arithmetic mean of all the absolute errors is taken as the final or mean absolute error of the value of the physical quantity a. When two quantities are added or subtracted, the absolute error in the final result is thesums of the absolute errors in the individual quantities. The relative error in a physical quantity raised to the power k is the k times the relative error in the individual quantity.

The significant figures are normally those digits in a measured quantity which are known reliably plus one additional digit that is uncertain. For counting of the significant figure rule are as: i All non- zero digits are significant figure.

But such zeros are significant if they come from a measurement. Single zero conventionally placed to the left of the decimal point is not significant. In addition or subtractionthe result should be reported to the same number of decimal places as that of the number with minimum number of decimal places.

In multiplication or division, the result should be reported to the same number of significant figures as that of the number with minimum of significant figures. Accuracy refers to the closeness of a measurement to the true value of the physical quantity and precision refers to the resolution or the limit to which the quantity is measured. The accuracy of a measurement is a measure of how close the measured value is to the true value of the quantity.

While rounding off measurements the following rules are applied Rule I: If the digit to be dropped is smaller than 5,then the preceding digit should be left unchanged. For ex: 9. For ex: 5. M 1 L 1 T -2 is the dimensional formula of Force. Dimensional Costants: These are the quantities which possess dimensions and have a fixed value.

Ex: Gravitational Constant.

Dimensional Variables: These are the quantities which possess dimensions and do not have a fixed value For ex: velocity, acceleration etc.

Dimensionless Constants: these are the quantities which do not possess dimensions and have a fixed value. Dimensionless Variables: These are the quantities which are dimensionless and do not have a fixed value.

### Practice Zone : Units & Dimensions

For ex: Strain, Specific Gravity etc. A given physical relation is dimensionally correct if the dimensions of the variousterms on either side of the relation are the same. They have to be determined either by experiment or by mathematical investigation.What is the power of a W bulb in cgs units? Electron volt is a unit of. One torr is equal to. The dimensional formula of energy and torque respectively are.

If L is the inductance and C is the capacitance, then the dimensional representation of expression will be. Which of the following quantities is expressed as force per unit area?

The ratio of the height of a man to the radius of the earth is of the order of. A spherometer has equal divisions marked along the peripheri of its disc and one full rotation of the disc advances on the main scale by 0. The least count of the system is. A vernier caliper has its main scale of 10 cm equally divided into equal parts.

If vernier scale of 25 divisions coincides with 12 mm on the main scale. The least count of the instrument is. The vernier of a circular scale is divided into 30 divisions which coincides against 29 main scale divisions. Each main scale divisions is The least count of the instrument is. The velocity of a particle is given by The unit of b will be.

The dimensions of in the equation where P is pressure, x is the distance and t is time are. In the International System of Units, the magnetic permeability is measured in. The number of significant figures in 0. The number of significant figures in m is. With due regard for significant figures, The value of 0. The sides of a rectangle are 6.Ans : 1. All above. Magnetic susceptibility 3. Angular acceleration 4. Moment of a magnet. Fermi is equal to. Impulse 2. Angular acceleration 3. Luminous intensity 4.

Which of the following is a common unit of a physical quantity in M. I systems. The fundamental unit which is common in F. S and M. S systems is.

Ans 1. Light year. Time and temperature 2. Length and time. Magnetic induction and magnetic flux differ in the dimensions of.

Electric current 4.Question No : 1 Which of the following does not have the same dimension? Question No : 2 The ratio of the dimension of Planck's constant and that of moment of inertia is the dimension of. Question No : 3 Out of the following pair, which one does not have the same dimensions? Question No : 4 Parsec is the unit of. Question No : 5 A. Specific gravity of a fluid is a dimensionless quantity R. It is the ratio of density of fluid to density of water. Question No : 7 Which of the following is not a unit of Young's modulus?

Explanation are given for understanding. A Electric flux, electric field, electric dipole moment. B pressure, stress, Young's modulus.

C Electromotive force, potential difference, electric voltage. D Heat, potential energy, work done. Share this question with your friends. A time. B frequency. C angular momentum. D velocity. A angular momentum and Planck's constant. B impulse and momentum. C moment of inertia and moment of force. D work and torque. B distance. C frequency. D angular acceleration. A both A and R are correct and R is the correct explanation of A. B both A and R are correct but R is not the correct explanation of A.

C A is correct but R is false. D both A and R are false.The maximum error in measurement of g is. If radian correction is not considered in specific heat measurement.

The measured value of specific heat will be. Three measurements 7. If P represents radiation pressure, c represents speed of light and Q represents radiation energy striking a unit area per second, then non-zero integers x, y and z, such that P x Q y c z is dimensionless, may be.

The time in which the velocity of the body increases from zero to 0. In specific resistance measurement of a wire using a meter bridge, the key k in the main circuit is kept open when we are not taking readings. The reason is. The error in the resistance has a maximum value of.

You must be logged in to post a comment. On the basis of dimensional equation, the maximum number of unknown that can be found, is A one B two C three D four 4. The multiplication of The measured value of specific heat will be A more than its actual value.

B less than its actual value. C remains same as actual value.

**Measurements Questions and Answers - MCQsLearn Free Videos**

D none of these. The S. Which of the following is a possible dimensionless quantity? The reason is A the emf of cell will decrease. B the value of resistance will change due to joule heating effect. C the galvanometer will stop working. Leave a Reply Cancel reply You must be logged in to post a comment.Mechanical Engineering 1. MCQ Practice Tests. Timed Mock Tests. Online Quizzes.

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