What Is Resistivity \( R\propto l \) \( R\propto \frac{1}{a} \) \( \text{So, }R\propto \frac{\ell }{a} \) \( \text{or }R=\rho \times \frac{\ell }{a}\text{ }………\text{ (i)} \) where ρ (rho) is called resistivity of the material of conductor. If,        l …

How The Human Eye WorksHuman eye is the most delicate and complicated natural optical instrument which enables us to see the wonderful world of light. Diagram shows the section of a human eye by a horizontal plane. It is a spherical ball of diameter ab…

Power Of Accommodation Of EyeThe ability of the eye lens to adjust its focal length is called accommodation. However, the focal length of the eye lens cannot be decreased below a certain minimum limit. To see an object comfortably and distinctly, you mus…

Understanding PhysicsHow does a rocket fly into the outer space? How does a boat float on the sea? How do kids jump about using pogo sticks? All these questions and many other daily observations are related to physics concepts.Physics is a branch of sci…

Some Common Measuring Instruments The measuring tape is used to measure lengths of several meters. Measurements are accurate up to 0.01 m. It is suitable for measuring the distance jumped by a long jumper, the distance of the throw of a javelin and the h…

Earth’s Gravitational ForceThe force which earth exerts on a body is called ‘force of gravity’. i.e. \(F=\frac{GMm}{{{R}^{2}}}\) Where M = mass of the earth, R = radius of the earth.Due to this force, a body released from some height on the earth’s surfa…

Newton’s Law Of Universal GravitationAny two particles in the universe attract each other. This force is called the force of gravitation. This concept was given by Newton. According to newton, “Any two bodies in universe attract each other with a force d…

Different Forms Of EnergyThe change of one form of energy into another form of energy is known as transformation of energy.Heat energy: Burning of fuels like diesel or petrol in vehicles provides heat energy to do work.Electrical energy: Electric motors …

Circular MotionWhen a body moves in such a way that its distance from a fixed point always remains constant, then its motion is said to be the circular motion.Uniform circular motion: If the radius vector sweeps out equal angles in equal times, then its…

Force of FrictionIf the switch off the engine of car it will stop after moving a certain distance. It means that some retarding force is acting on the car which stops it. The force opposing the motion of the car is called “force of friction”.The frictio…