What is Electromotive Force (Emf)? What is its role in Physics?

Electromotive Force

When a steady current is to be passed through a resistance, a constant potential difference must be maintained across its ends.

An electric cell is a device which can maintain a constant potential difference across its ends. The cell converts its chemical energy into electrical energy and transfer its energy to the resistance connected its ends. This energy is dissipated as heat in the resistance.

The positive charge carriers in the current fall from high to low potential across resistance. The cell lifts these charges from low potential and puts them again at higher potential. This influence of the cell that makes the charge move from low potential to higher potential is known as electromotive force (EMF).

Quantitatively EMF is the potential difference across the terminals of a cell when the cell is in open circuit i.e.,   when it is not delivering any current.

How to find Image of a point in a line? Best trick

Image of a Point in a Plane :

Let P and Q be two points on given plane such that 

(i)     line PQ is perpendicular to the plane and

(ii)    mid point of PQ lies on the plane

Then either of the point is the image of the point in the plane.

Algorithm For Finding the image of a point in a given Plane :

Step I: Write the equation of the line passing through P and normal to the given plane

Step II: Write the coordinates of image Q as (x1 + ar, y1 + br, z1 + cr)

Step III: Find the coordinates of the mid-point of PQ.

Step IV: Obtain the value of r by putting the coordinates of mid point in the equation of plane.

Step V: Put the value of r in the coordinates of Q.