Capacitance and the parallel plate capacitorAQA A-Level Physics: Mind map

Exam questions on Capacitance and the parallel plate capacitor

1. A 470 µF capacitor is connected across a 12 V d.c. supply until it is fully charged.
   Define the capacitance of a capacitor and state what the charge Q in the definition refers to.2 marks
2. A parallel plate capacitor has two identical square plates, each of area 0.020 m², separated by an air gap of 0.50 mm. Treat the relative permittivity of air as 1.0. ε₀ = 8.85 × 10⁻¹² F m⁻¹.
   A sheet of dielectric of relative permittivity 4.0 is inserted so that it completely fills the gap. Calculate the new capacitance.2 marks
3. An air-filled parallel plate capacitor has a capacitance of 2.4 nF. It is charged to 160 V and then disconnected from the supply. A sheet of dielectric made of polar molecules is then slid between the plates so that it fills the gap, and the capacitance rises to 9.6 nF.
   Explain how the polar molecules of the dielectric increase the capacitance of the capacitor.3 marks