Chapter 21 - Capacitance

Question 1

After some time, what does the potential difference across the capacitor become

Answer 1

The EMF of the cell.

Question 2

If there are other components in parallel with a capacitor and it is fully charged, what does the p.d across those components become

Answer 2

0V

Question 3

When a capacitor is fully charged, what is the current in the circuit

Answer 3

0A

Question 4

Use Fig. 22 to determine the capacitance C of the capacitor. Describe how the student can
then use this value of C to determine a value for ε.
In your description, mention any additional measurements required on the capacitor

Answer 4

C = A/d
 A = area (of overlap) and d = separation.
 Use ruler to measure the side / radius / diameter (and
hence the area A)
 Ensure total overlap of plates.
 Measure the thickness / d of paper using micrometer /
(vernier) caliper.
 Take several readings of thickness and determine an
average value for d