A parallel plate capacitor is made of two rectangular aluminium sheets of lateral dimensions 500 mm and 20 mm. The space between the plates is filled with

polystyrene and the separation between plates is 0.15 mm. Calculate the capacitance of the capacitor and the value of the maximum potential difference that can be applied across the capacitor without dielectric breakdown. Take the dielectric constant of polystyrene as 2.6 and the value of the maximum electric field that

polystyrene can withstand as 25×10⁶ Vm⁻¹.

A uniform plane wave of 100 kHz travelling in free space strikes a large block of a material having

ε = 4 ε₀ , µ = 9µ₀ and σ = 0 normal to the surface. If the incident

magnetic field vector is given by

B = 10^-6 cos (ωt − βy) zˆ tesla

write the complete expressions for the incident, reflected, and transmitted field vectors.

Explain the terms polarisation surface charges and molecular polarisability for a

dielectric material.

If the space between the plates of a capacitor is filled will a dielectric material, does

it affect the value of capacitance? Justify your answer.

Two concentric thin metallic spheres having radii 30 cm and 20 cm carry 10 µC and

5 µC, charges respectively. Calculate the electric potential at a distance of 25 cm

from the centre of the spheres.

The radius of the wire in a coaxial cable is 0.65 mm and the inner radius of the coaxial conducting cylinder is 1.45 mm. Assuming that there is vacuum between the

wire and the cylinder, calculate the capacitance of a 1.5 m length of the cable.

A long, straight wire of radius 5.0 mm carries a current of 20A. i) Calculate the magnetic field at the surface of the wire, and ii) calculate the perpendicular distance, from the axis of the wire, at which the magnitude of magnetic field will be half of

its value at the wire surface.