In a meter bridge experiment null point is obtained at $$20\,cm.$$ from one end of the wire when resistance $$X$$ is balanced against another resistance $$Y.$$ If $$X < Y,$$ then where will be the new position of the null point from the same end, if one decides to balance a resistance of 4 $$X$$ against $$Y$$
A.
$$40\,cm$$
B.
$$80\,cm$$
C.
$$50\,cm$$
D.
$$70\,cm$$
Answer :
$$50\,cm$$
Solution :
In the first case $$\frac{X}{Y} = \frac{{20}}{{80}} = \frac{1}{4}$$
In the second case $$\frac{{4X}}{Y} = \frac{\ell }{{100 - \ell }} \Rightarrow \ell = 50$$
Releted MCQ Question on Electrostatics and Magnetism >> Electric Current
Releted Question 1
The temperature coefficient of resistance of a wire is 0.00125 per $$^ \circ C$$ At $$300\,K,$$ its resistance is $$1\,ohm.$$ This resistance of the wire will be $$2\,ohm$$ at.
The electrostatic field due to a point charge depends on the distance $$r$$ as $$\frac{1}{{{r^2}}}.$$ Indicate which of the following quantities shows same dependence on $$r.$$
A.
Intensity of light from a point source.
B.
Electrostatic potential due to a point charge.
C.
Electrostatic potential at a distance r from the centre of a charged metallic sphere. Given $$r$$ < radius of the sphere.