## Wednesday, 17 September 2014

### Current Electricity

1. Derive the formula for combination of resistors in series and parallel.
2. Describe the experimental procedure to determine the internal resistance of a cell using potentiometer.
3. Derive the formula for combination of cells in series, parallel and mixed grouping.
4. Derive the expression for balanced wheat stones bridge P/Q = R/S
5. Draw a neat and labelled diagram of a simple potentiometer used to measure the e.m.f of a cell and explain the experimental procedure.
6. How can a moving coil galvanometer is converted into:
a) an ammeter                             b) a voltmeter of  given ranges
Draw labelled diagram, illustrate the conversion, and derive the value of resistor to be attached.
7.  State Kirchaff’s I & II law .
8. A galvanometer coil has a resistance of 15Ohm and it shows full scale deflection for a current of 4 mA.   How will you convert it into an ammeter of range 0 to 6A?           (10 M ohm)
9. What would be the resistance of the resistor that is colour coded Red-Red-Orange?
10. A galvanometer with a coil of resistance 100Ohm and a scale having 100 division has a current sensitivity of 25micro Ampere per division.   How will you convert it into an ammeter of range 0 to 5 A?                          [0.05 Ohm]