2016 Feb

Field: Force at a Distance

February 16, 2016

Force Field at a Distance

If I have to impart a force on an object, we generally do it by getting in contact with it. Let’s say you are playing a game of cricket, to impart force on the ball and hit it, you need to get the ball in contact with the bat. This is the same in the case of badminton where you have to hit a shuttle. Do we always have to touch an object to impart force on it? For example, an airplane engine generates enough power to push away or suck things but we do not see the engine in contact with those objects. Well, we can simply explain it by saying that the air present in the atmosphere mediates the effect. Now consider the case of a compass needle moved without any contact at all, this happens even in vacuum where there is no air present. How does this work? This is mediated by something called as field. Let’s discuss the concept of field and different types of fields in detail in this article.

Field can be thought of as force at a distance. For the field to exist, no medium is required and the force can be effected without contact. As we have learnt in our JC Physics tuition classes, there are three different types of fields – magnetic, electric and gravitational. Magnetic field and electric field are of both attractive and repulsive types i.e. an object under the influence of the magnetic field can either be attracted or repelled depending on the nature of the object. But in the case of gravitational field the objects can only be attracted and the concept of repulsion doesn’t apply here. All the three fields are associated with forces that decrease with an increase in the distance i.e. inversely proportional to the square of the distance between the object imparting force and the object on which the force is imparted.

Gravitational force is directly proportional to the product of the masses of the objects involved whereas magnetic field depends on something called as pole strength (remember magnets come with two poles south and north). Electric field is directly proportional to the product of the charges involved. Electric and magnetic fields are related and time varying magnetic field produces electric field and vice versa. The relation between electric and magnetic fields inspired people to unify all the three major fields known by including gravitational field to the bunch. Albert Einstein explained gravity by the curvature of space-time in the process.

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