# All IGCSE Physics Laws

## Hooke’s law

Hooke’s law states that when an object is stretched, its extension is directly proportional to the load force. Hooke’s law only applies if you do not stretch an object beyond its elastic limit.

## Newton’s Law of Motion: 1st Law

An object will continue in a state of rest or uniform motion in a straight line unless an external force acts upon it.

## Newton’s Law of Motion: 2nd Law

The rate of change of momentum of an object is directly proportional to the force acting and takes place in the direction in which the force acts.

## Newton’s Law of Motion: 3rd Law

Every action has a equal and opposite reaction.

## Ohm’s law

The current flowing in a metallic conductor is directly proportional to the potential difference applied across its ends, provided that the physical conditions are constant.

## Law of Reflection

i.The incident ray, the reflected ray and the normal to the surface all lie in the same plane.

ii.The angle of incidence is equal to the angle of reflection

## Law of Refraction

i.The incident ray, the reflected ray and the normal to the surface all lie in the same plane.

ii.For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant i.e,

sin i/sin r = constant

## Newton’s Law of Gravity

Newton suggested that between any two objects there is a force of attraction. This attraction is due to the masses of the objects. He called this force gravitational force. The size of the force depends on:-

i.The masses of the objects

ii.The distance between the masses

## Conservation of Momentum

For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.

## Law of Conservation of Energy

Energy is not created or destroyed in any process. It is just converted from one type to another.

## Right hand grip rule

With the thumb of your right hand pointing to the direction of the current where your fingers will curl in the direction of the field.

## Fleming’s left hand rule

Hold the forefinger, second finger and the thumb of your left hand at right angles to each other while the others closed. If the thumb points in the direction of the motion of force, the first finger points in the direction of the field (N to S) then the second finger will point in the direction of the current.

## Faraday’s Law of Electromagnetic Induction

The size of the induced voltage across the ends of a wire (coil) is directly proportional to the rate at which the magnetic flux lines are being cut.

## Lenz’s Law

The direction of the induced e.m.f and hence the induced current in a closed circuit is always such as to oppose the change in magnetic flux producing it.

Category: Science
Tags: igcse, physics laws