Page 58 - Physics - XII

3. Assembly of electric components in the electric circuit is complete. Check the continuity of the circuit
using a multimeter.

Result
Assembly of all the components in the electric circuit is complete.

Precautions

1. Ammeter is connected in series in the circuit.
2. Voltmeter is connected in parallel with the given resistor.

ACTIVITY - 5

Aim

To study the variation in potential drop with length of a wire for a steady current.

Apparatus and Materials Required
A potentiometer, a voltmeter, an ammeter, a battery of constant voltage, a one-way key, a rheostat,
a jockey, and connecting wires

Rheostat

B 400 cm
+ Resistance
Ammeter A wire 300 cm Copper strips
– J (Jockey)
200 cm
K . Key A
0 cm 100 cm

– + + V –
Battery Voltmeter

Fig. 5.1: Variation of potential drop with length of a wire

Principle/Theory
If a steady current is fl owing through a wire having resistance per unit length constant and of uniform

cross-sectional area, then the potential drop V across two points of the wire is directly proportional to the
length l between these two points.
V
i.e. V ∝ l ⇒ V = φl ⇒ , φ is called potential gradient
l
Procedure
1. Arrange the components as per the circuit diagram shown in the Fig. 5.1. Treat the end A of potentiometer
wire where positive terminal of battery has been joined as origin (zero) for the purpose of measuring

length.
2. Calculate the least count of voltmeter and ammeter. Note the zero correction for voltmeter and ammeter.
3. Now, insert the key K, and press the Jokey J at the end B of potentiometer wire and adjust the rheostat
so that reading of voltmeter is maximum, but well within the scale.

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