Choose the correct option from the following options given below :

Nucleus A is having mass number 220 and its binding energy per nucleon is 5.6 MeV. It splits in two fragments 'B' and 'C' of mass numbers 105 and 115. The binding energy of nucleons in 'B' and 'C' is 6.4 MeV per nucleon. The energy Q released per fission will be :

A parallel plate capacitor is formed by two plates each of area 30$$\pi$$ cm² separated by 1 mm. A material of dielectric strength 3.6 $$\times$$ 10⁷ Vm^$$-$$1 is filled between the plates. If the maximum charge that can be stored on the capacitor without causing any dielectric breakdown is 7 $$\times$$ 10^$$-$$6C, the value of dielectric constant of the material is :

[Use $${1 \over {4\pi {\varepsilon _0}}} = 9 \times {10^9}$$ Nm² C^$$-$$2]

The magnetic field at the centre of a circular coil of radius r, due to current I flowing through it, is B. The magnetic field at a point along the axis at a distance $${r \over 2}$$ from the centre is :