Page 59 - Physics - XII

4. Slide the Jockey J along the wire away from end A. Note the reading of voltmeter after every 40 cm.
5. Repeat the observations by placing the Jockey at the lengths 80 cm, 120 cm up to 400 cm.
V
6. Calculate the ratio for each observation. Plot a graph between V and l taking l along X-axis and V
along Y-axis. l

Observations
Range of voltmeter = 0 to _____ V

Least count of voltmeter = _____ V
Zero correction of voltmeter = _____ V

Table to study the variation of potential drop with length

Voltmeter reading (volt) Potential gradient
S. Length of wire φ φ = V
No. l (cm) Observed (V) Corrected (V) l
(volt cm )
–1
1.

2.

3.

4.

.

.

.

Mean value of potential gradient = φ = _____ V/cm.

Graph and Calculations
A graph is plotted between V and l, taking l along Scale used on:
X-axis and V along Y-axis, as shown in Fig. 5.2. The Y X-axis, 1 cm = ... cm
graph comes to be a straight line. The slope of the line gives potential Y-axis, 1 cm = ... volt
gradient φ.

Result
V
The ratio is almost constant and the graph between V and l is V (in volt)
l
a straight line. These two results show that the fall of potential is
directly proportional to the length of the wire. X
l (in cm)
Hence, V ∝ l. Fig. 5.2: Graph between V and l

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