Neet PYQ 2007

Two radioactive substances $A$ and $B$ have decay constants $5\lambda$ and $\lambda$ respectively. At $t=0$ they have the same number of nuclei. The ratio of the number of nuclei of $A$ to those of $B$ will be $1/e^2$ after a time interval:

A hollow cylinder has a charge $q$ coulomb within it (at the geometrical centre). If $\varphi$ is the electric flux associated with the curved surface $B$, the flux linked with the plane surface $A$ is:

A transformer is used to light a $100\text{W}$ and $110\text{V}$ lamp from a $220\text{V}$ mains. If the main current is $0.5\text{A}$, the efficiency of the transformer is approximately:

A charged particle (charge $q$) is moving in a circle of radius $R$ with uniform speed $v$. The associated magnetic moment $\mu$ is given by:

A particle of mass $m$ moves in the $XY$ plane with a velocity $v$ along the straight line $AB$. If the angular momentum of the particle with respect to origin $O$ is $L_A$ when it is at $A$ and $L_B$ when it is at $B$, then: