Page 136 - Physics - XII

7. Measure the distance between the balls when they become stationary and note the distance.
8. Touch any one suspended ball with other uncharged third ball and take the third ball away and repeat

step 6.
9. Touch other suspended balls with other uncharged fourth ball and take the fourth ball away and repeat
the step 6.
10. Note the distance between balls each time and determine the charge in each case.

Observations
Mass of each ball, m = _____ g
Radius of each ball, r = _____ mm
Length of each thread, l = _____ cm

Table for Measuring the Charges on Balls A and B, and Distance Between the Balls

S. No. Charge on ball A Charge on ball B Distance between the balls, a (cm)

1. 0 0 0

2. q q a = _____ cm
1
3. q q/2 a = _____ cm
2
4. q/2 q/2 a = _____ cm
3

Calculations 3
Calculate the charge in each case using the relation q mga , K 1
2l K 4 0
Result

The charge on each ball = _____ C

Precautions
1. The length of the thread with which the balls are suspended should be equal.

2. Do not touch the suspended balls by any conducting body.
3. The glass rod should be rubbed properly with the silk cloth.
4. Measure the mass of the balls accurately.

Sources of Error
1. The balls may not be of equal mass and size.
2. The distance between the balls may not be measured accurately.

PROJECT - 7

Aim

To study the factor on which the self-inductance of a coil depends by observing the eff ect of this coil, when
put in series with a resistor/(bulb) in a circuit fed up by an A.C. source of adjustable frequency.

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