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# Properties of a force field

Properties of a Force Field

(i) Properties of Gravitational Field

(a) The lines of force are directed towards the centre of the planet; hence, it is a radial field.

(b) The gravitational force field (field strength) ‘g’ at a point is the force per unit mass placed at that point. i.e, g=Fm in N/kg but the S.I unit is m/s2

(c) Any force acting on a body falling towards the centre of the earth is given by F = mg

(d) Gravitational field is a vector quantity.

(ii) Properties of Magnetic Field

(a) Direction: When a magnet is freely suspended, it comes to rest in the South-North direction of the earth.

(b) Attraction: A magnet has the ability to attract magnetic materials e.g, steel, iron, etc.

(c) Force: A magnet exerts force on other magnets in such a manner that like poles repel and unlike poles attract.

(d) The inseparable nature of poles on the magnetic dipoles: If a magnet is broken into small pieces, however small it may be, it will still have a North and South Poles. The smallest bit of a magnet is a dipole.

(e) Magnetic lines of force originate from the North pole and terminate at the South pole.

(iii) Properties of Electric Field

(a) Electric lines of force originate from a positive charge and terminate in a negative charge.

(b) Electric lines of force never cross each other.

(c) They repel each other side ways.

(c) They are in a state of tension which tends to shorten them.

(d) The electric field at a point is defined as the force per unit charge placed at that point. i.e, ε=Fq measured in Newton per Coulomb N/C

EVALUATION

1. State two properties each of the three vector fields discussed.
2. What is the direction of the magnetic lines of force?
3. What is the unit of electric field strength?

GENERAL EVALUATION

1. Discuss the properties of the magnetic flux.
2. Define the electric field strength.
3. Itemise the three vector fields.
4. Why is electric When a field is represented by lines of force, it is then calledlines of force a vector quantity?