To determine the resistivity of 2/3 wire by plotting a graph between V & I | Class 12 | Physics Practical Copy | Handwritten with observations

By

 


Aim: To determine the resistivity of 2/3 wire by plotting a graph between V & I.


01

Principal:

According to Ohm's law the electric current flowing through a conductor is directly proportional to the potential difference across its ends, provided that the physical condition of the conductor remains constant.
Let I be the current flowing through the conductor and V be the potential difference across its ends, then according to Ohm's law
V ∝ I
V = RI
[eq.1]
where R is the proportionality constant and is called Resistance of the conductor. 


02

The SI Unit of resistance is ohm and is denoted by (Ω) in the honor of George Simon Ohm. The resistance, R depends upon the material and dimensions of the conductor. For a given wire of uniform cross-section, the resistance depends on its length l and the area of cross-section A of the wire. It also depends on the temperature of the conductor. At a given temperature the resistance
R = ρ
l
A
[eq.2]
where ρ is the specific resistance or resistivity and is characteristic of the material of wire.

03
Note: The resistance R do not depend upon the current I flowing and the voltage V across the conductor.
A straight line passing through the origin is obtained when the values of V and I is plotted on V-I graph.
Hence, the resistivity of the given wire is given by
ρ = (
A
l
)R


04

Procedure:

  1. Clean the ends of the connecting wires with the help of sandpaper to remove any insulating coating on them.
  2. Connect all the components according to the circuit diagram.

    05

  3. Note whether pointers in milliammeter and voltmeter coincide with the zero mark on the measuring scale. If it is not so, adjust the pointer to coincide with the zero mark by adjusting the screw provided near the base of the needle using a screwdriver.
  4. Note the range and least count of the given voltmeter and milliammeter.
    06

  5. Insert the key K and slide the rheostat contact to one of its extreme ends, so that current passing through the resistance wire is minimum.
  6. Note the milliammeter and voltmeter readings.
    07
  7. Remove the key K and allow the wire to cool, if heated. Again, insert the key. Shift the rheostat contact slightly to increase the applied voltage. Note the milliammeter and voltmeter reading.
    08
  8. Repeat step 7 for four different settings of the rheostat and record your observations.

09


●Other Experiments


No comments:

Post a Comment