Conversion of Units

The primary focus of this chapter is to tackle conversion of units of measurement of various quantities. However, before we start, it is essential to understand fundamental and derived physical quantities and their units. 

In order to learn how to convert units of physical quantities, it is necessary to be aware of the terms – dimensional formula and dimension equation. Firstly, check these details about fundamental and derived quantities.

Fundamental Quantities and Derived Quantities

All measurable physical quantities can be primarily classified into two types which are –

  • Fundamental Quantities

A small group of physical quantities are considered as fundamental quantities or primary quantities which are used to derive other physical quantities. 

For Example:

Mass, time, length, electric current, luminous intensity of light, temperature, amount of substance are all fundamental quantities.

  • Derived Quantities

Also referred to as secondary quantities, derived quantities are formed from primary or fundamental quantities. 

For Example:

On dividing distance by time we can calculate the speed of an object. Hence, speed is a prime example of a derived quantity. 

Additionally, if we multiply the breadth, length and height of an object, we get to derive the volume. So, volume is also another example of a derived quantity.

Fundamental and Derived Units

Units selected for primary physical quantities are known as fundamental units. Meanwhile, those units which are formed with the help of fundamental units are termed as derived units. 

For Example:

Speed is a derived quantity whose unit is determined as distance/time, i.e. metre/second. Here, you can notice that metre and second are fundamental units while the unit of speed, i.e. metre/second is a derived unit. 

A Complete Unit Conversion Table

In order to solve numerical problems in case of unit conversion questions in physics, consulting a tabulated form of unit conversions is highly important especially for beginners. 

Several tables containing unit conversion formula are given below which sums up almost every important physical quantity. Each table contains various units and their conversions of a specific physical quantity, fundamental or derived.

Basic Unit Conversion Table – Length

Sl. No.

Different Types of Measurement

In Terms of Metre

1.

1 mm

1 x 10-3 m

2.

1 km

1 x 103 m

3.

1 inch

2.54 x 10-2 m

4.

1 foot

3048 x 10-4 m

5.

1 light year

946 x 1013 m

6.

1 mile

16 x 102 m

7.

1 angstrom

1 x 10-10 m


Unit Conversion List – Mass

Sl. No.

Different Types of Measurement

In Terms of Gram

1.

1 mg

1 x 10-3 g

2.

1 kg

1 x 103 g

3.

1 stone

6.35 x 102 g

4.

1 pound

4.53 x 102 g

5.

1 ounce

0.283 x 102 g


Units of Measurement Conversion Table – Volume

Sl. No.

Different Types of Measurement

In Terms of Litre

1.

1 ml

1 x 10-3 l

2.

1 kl

1 x 103 l

3.

1 cubic inch

1639 x 10-5 l

4.

1 cubic foot

0.283 x 102 l

5.

1 gallon

0.03785 x 102 l


Units and Conversions – Time

Sl. No.

Different Types of Measurement

In Terms of Seconds

1.

1 min

60 s

2.

1 hour

3600 s

3.

1 day

86400 s

4.

1 week

604800 s

5.

1 month

2592000 s

6.

1 year

31104000 s


Unit Conversion Table – Energy

Sl. No.

Different Types of Measurement

In Terms of Joule

1.

1 kw-hr

3.6 x 106 J

2.

1 erg

1 x 10-7 J

3.

1 BTU

1.055 x 103 J

4.

1 calorie

4186 x 10-3 J

5.

1 electron volt

1.602 x 10-19 J


Numerical Problems from Unit Conversion Tables

Numerical problems on the conversion of units in physics are quite common in the exams. For example, the following question is frequently asked –

  1. State the Relationship Between Dyne and Newton?

As we know, dyne and Newton are units of force. Moreover, the dimensional formula of force is [MLT-2]. 

Hence, 1 Newton = 1 x kg x m x s-2 = 1 x 103 g x 103 cm x s-2 = 1 x 106 g x cm x s-2

So, Newton = 106 dyne.

At Vedantu, we hope that this discussion on Conversion of Units will help you to attain high marks in the upcoming physics exams. Moreover, make sure to download our Vedantu app to access study materials and online classes easily.

FAQ (Frequently Asked Questions)

1. Name Four Fundamental Quantities in Physics?

Ans. Four fundamental quantities in physics are mass, length, time, temperature, etc.

2. What is the Difference Between One Pound and One Ounce?

Ans. One pound equals to 4.53 x 102 grams while one ounce can also be measured as 0.283 x 102 grams

3. How Many Litres of Diesel Will Make One Gallon?

Ans. 0.03785 x 102 liters of diesel will make one gallon of diesel.