JAMB Physics 2011 Paper

Concept:The dielectric constant measures how much a material increases a capacitor's capacitance compared with air.It is the ratio of capacitance with the dielectric to capacitance in air.Explanation:Let $C_0 = 20\ \mu F$ be the capacitance in air.Let $C = 60\ \mu F$ be the capacitance when the dielectric is present.The dielectric constant $k$ is given by the formula:$$k = \frac{C}{C_0}$$Substitute the given values:$$k = \frac{60\ \mu F}{20\ \mu F} = 3$$The unit $\mu F$ cancels out, leaving a pure number.So the dielectric constant is $3.0$.Answer:The dielectric constant is $3.0$.Correct option: C. 3.0.