A battery supplies 0.9 A current through a $2 \Omega$ resistor and 0.3 A current through a $7 \Omega$ resistor when connected one by one. The internal resistance of the battery is

A particle of mass $m$ and charge $q$ describes a circular path of radius $R$ in a magnetic field. If its mass and charge were $2 m$ and $\frac{q}{2}$ respectively, the radius of its path would be

Which of the following pairs is that of paramagnetic materials?

A galvanometer of resistance $50 \Omega$ is converted into a voltmeter of range $(0-2 \mathrm{~V})$ using a resistor of $1.0 \mathrm{k} \Omega$. If it is to be converted into a voltmeter of range ( $0-10 \mathrm{~V}$ ), the resistance required will be