Current electricity-II : Current electricity-II BY R.Buvana
Current electricity : Current electricity 1.Kirchoff’s law
2.Wheat stone bridge
3.Metre bridge
4.Potentiometer
5.Homework questions
Kirchoff’s laws : Kirchoff’s laws First law-Junction law or current law
?I=0
Second law-closed loop law or voltage law
?E=?IR
Wheatstone bridge : Wheatstone bridge It is one of the accurate arrangements for measuring an unknown resistance
For a balanced bridge, it can be proved that
P/Q=R/S
Potentiometer : Potentiometer A potentiometer is used to compare emf’s of two cells or to measure internal resistance of a cell.
Principle-When a constant current is passed through a wire of uniform area of cross-section,the potential drop across any portion of the wire is directly proportional to the length of that portion.
Homework questions : Homework questions Derive the relationship between the current and drift velocity and define the unit of charge.
Two point charges A and B of values 5x 10?? C and 3x 10??C are kept 6 cm apart in air. Calculate the work done when charge B is moved by 1 cm towards charge A..
Explain the grouping of cells (i) in series and (ii) in parallel. Obtain the condition for the maximum current in the external resistance connected with each grouping of cells.
Homework questions : Homework questions If a wire is stretched to double its original length without loss of mass how will the resistivity of the wire be influenced?
Are the paths of electrons straight lines between successive collisions (with the positive ions of the metal) in the i) absence of electric field ii) the presence of E.F.
A wire is carrying current. It is charges? Why?
Some times the balance point in the potentiometer many not be obtained on the wire. Explain.
It is easier to start a car engine on a warm day than on a chilly day why?
How can you make a potentiometer of given wire length more sensitive using a resistance box?
Why do we prefer a potentiometer with a longer bridge wire? What are the characteristic of a fuse wire?