All points on a conductor carrying static charge are at the same potential. If charges were at different potentials on a conductor, they would move, and therefore would not be static.When they come to rest they must all be at the same potential. Charge will only move when there is potential difference between two points and a conductor connecting those points. Charge always moves towards the point at lower potential.
SAMPLE PROBLEM 16A
A potential difference of 12 V exists between two points. Find the work done in transferring 5 C of charge between the points.
Q1 What is the potential difference between two points when 12 J of work is done in moving 3 C of charge from one point to the other?
Q2 An electron loses 8 1018 J of energy as it moves through a certain voltage. Given that the charge on an electron is 1.6 1019 C, calculate the voltage.
Q3 Calculate the work done in moving a 5 C charge across a potential difference of 5 kV. Measuring potential difference
A voltmeter is used to measure voltage. In order to measure the potential difference across a component the voltmeter is connected in parallel with that component. The circuit symbol for a voltmeter is
V Electromotive force
ELECTROMOTIVE FORCE An electromotive force (emf) is a voltage that is applied to a circuit.
SCIENCE,TECHNOLOGY & SOCIETY Sources of emf
A source (or seat) of emf is a device in which chemical, mechanical or some other form of energy is converted into electrical energy, e.g. a battery, an electric generator, etc.
Primary cells
In a primary cell chemical energy is converted into electrical potential energy.The emf of a particular cell is decided simply by its chemistry and does not depend on its size. Primary cells cannot be recharged.
