1. capacitors

2. CAPACITORS A device designed to store charge
The electrical symbol for a capacitor is …

3. A capacitor is made from two parallel plates placed near to each other and connected to a power source.
Electrons from the negative terminal flow to the attached plate and an equal number of electrons leave the other plate (the one attached to the positive terminal).
A potential difference is produced between the two plates but there is no direct connection so no current can flow.
A good insulating material is placed between the two plates, called the dielectric.

4. uses smoothing circuits back up power supplies timing circuits
pulse producing circuits
tuning circuits (radios)
filter circuits

5. Potential Difference (V)
Capacitance
Charge (x10-6 C)
Potential Difference (V)
300
0.3
600
0.65
900
0.9
1200
1.3
1500
1.5

6. Potential Difference (V)
Plot Q against V
Charge (C)
Potential Difference (V)

7. Farads
C = Q/V
The capacitance C of a capacitor is defined as the charge stored per unit potential difference.
Unit : F (Farad)
Most capacitors are in the micro range hence the capacitors you use will be in μF

8. CAPACITORS
A student inserts two bare copper wires into a lump of wet clay. the clay is dried out. The student suggests that he has made a capacitor. Explain why he is correct.
The charge stored by a capacitor connected to a 12V battery is
2.4 x 10-5 C. calculates its capacitance in farads and microfarads.
A capacitor stores a charge of 30pC when the p.d. across it is 3.2V. Calculate the charge stored in pC when the p.d is increased to 8.7 V
A capacitor of capacitance F is connected to a 1.5 V cell, Calculate the number of electrons delivered by the cell to the capacitor.