Page 123 - Physics - XII

Result

1. Internal resistance of given cell is directly proportional to distance between electrolyte.
2. Internal resistance of given cell is inversely proportional to area of electrodes immersed in electrolyte.
3. Internal resistance of given cell is inversely proportional to concentration of electrolyte.

Precautions
1. All the connections should be neat and tight.
2. All the plugs in the resistance box should be made tight.
3. Positive terminal of the voltmeter should be connected to the positive terminal of the cell.

4. The plugs should be inserted in one-way keys only at the time of taking observations.
5. While studying the eff ect of concentration of electrolyte, the distance between the electrodes and their
common area should remain unchanged.
6. While studying the eff ect of common area of the electrodes, the distance between the electrodes should

remain unchanged.

PROJECT - 2

Aim
To study the variations in current fl owing in a circuit containing an LDR because of a variation in

(a) the power of incandescent lamp used to ‘illuminate’ the LDR (keeping all the lamps at a fi xed distance).
(b) the distance of an incandescent lamp (of fi xed power) used to ‘illuminate’ the LDR.

Apparatus and Materials Required
Incandescent lamps of 25 W, 60 W, 100 W, and 200 W, an LDR, a multimeter, a metre scale, and a battery (6 V)

_
+
Key

Bulb

Light

LDR

I
+ –

Key
6 V
Battery Multimeter

Fig. 2.1: To study the variations in current fl owing in a circuit containing an LDR

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