A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring balance reads $$49 \mathrm{~N}$$, when the lift is stationary. If the lift moves downward with an acceleration of $$5 \mathrm{~m} / \mathrm{s}^2$$, the reading of the spring balance will be $$(\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2)$$

In a potentiometer experiement, when three cells $$\mathrm{A}, \mathrm{B}$$ and $$\mathrm{C}$$ are connected in series, the balancing length is found to be $$420 \mathrm{~cm}$$. If cells $$\mathrm{A}$$ and $$\mathrm{B}$$ are connected in series the balancing length is $$220 \mathrm{~cm}$$ and for cells $$\mathrm{B}$$ and $$\mathrm{C}$$ connected in series in balancing length is $$320 \mathrm{~cm}$$. The emf of cells $$\mathrm{A}, \mathrm{B}$$ and $$\mathrm{C}$$ are respectively in the ratio of

A current '$$I$$' is flowing in a conductor of length '$$L$$' when it is bent in the form of a circular loop, its magnetic moment will be

Two long conductors, separated by a distance '$$\mathrm{d}$$' carry currents '$$\mathrm{I}_1$$' and '$$\mathrm{I}_2$$' in the same directions. They exert a force '$$\mathrm{F}$$' on each other. Now the current in one of them is increased to two times and its direction is reversed. The distance is also increased to '$$3 \mathrm{~d}$$'. The new value of the force between them is