the convex lens and adjust its position to get a sharp, inverted and diminished image. Measure the distance between the screen and the lens (v). Repeat the same procedure, by changing the distance of the object (u) and tabulate your observations. f Practicals Observation: Focal length of the convex lens (By distance object method) is (f) = …………cm 2f = …….cm S.No Size of the Image Position of the object Distance between the object and the lens (u) cm Distance between the screen and the Lens (v) cm Focal length of convex lens = uv (u + v) cm f Diminished u > 2f Same size u = 2f Magnified u < 2f Result: The focal length of the given convex lens .
By distance object method f = ………cm . By ‘uv’ method f = … .…..cm . DETERMINATION OF RESISTIVITY Objective: To determine the resistivity of the material of the given coil of wire. Equipment required: A coil of wire, screw gauge, a metre scale, battery, key, ammeter, voltmeter, rheostat and connecting Wires.
Formula: The resistivity of the material of the coil of wire is Where A is the area of cross section of the wire (m ) L is the length of the coil of wire (m) ` R is the resistance of the coil of wire (ohm) Circuit Diagram: Procedure: Connect the battery, ammeter, given wire, rheostat and key in series, as shown in the circuit diagram. Connect the voltmeter in parallel to the unknown resistor. Close the key and hence the circuit is closed. Adjust the rheostat such that the ammeter reads a current of .
ampere. Note down the potential difference across the resistor as shown by the voltmeter. Adjust the rheostat and change the current in steps of .5A (that is .5A, .0A, .5A, etc.). For each current, note down the corresponding potential difference as shown by the voltmeter.
Tabulate the observations. Measure the diameter of the wire using a screw gauge. Measure the length