Practicing Success
When two resistances X and Y are put in the left hand and right hand gaps in a wheatstone meter bridge, the null point is at 60cm. If X is shunted by a resistance equal to half of itself then find the shift in the null point. |
16.7 cm 26.7 cm 36.7 cm 46.7 cm |
26.7 cm |
Arrangement is shown in the figure. $ \frac{X}{Y} = \frac{60}{40} = \frac{3}{2}$ When X is shunted then resistance in the left gap becomes
$ X'= \frac{X.X/2}{X+X/2} = \frac{X}{3}$ $ Now , \frac{X/3}{Y} = \frac{l}{100 - l} = \frac{1}{2}$ $ l = \frac{100}{3} cm$ $ Shift = 60 cm - 33.3 cm = 26.7 cm$ |