Capacitance

Capacitance

1. Charging and Discharging

2. Energy stored

   • Can be found by using the graph of p.d. against charge for the capacitor
   • E = (QV)/2

3. Investigating V and Q

   • By charging a capacitor using a constant current
   • Set up a test circuit with an Ammeter, Voltmeter and variable resistor
     • Adjust the resistor to keep the charging current constant
       • Record the p.d. at regular time intervals until it equals the battery p.d.
         • Plot current against time
           • The area under the graph is the charge stored

4. Capacitance/ Capacitors

   • Capacitance is the amount of charge an object is able to store per unit p.d. across it
   • Capacitor
     • An electrical component that stores electrical charge
     • 2 electrical conducting plates separated by a dielectric.
       • A dielectric is an electrical insulator
     • When charged by a d.c. power source, the charge builds up over the plates
       • One plate becomes negatively charged and the other becomes positively charged
       • The plates are separated by a dielectric so a p.d. build up
     • It will only charge up to the voltage of the power source
   • C = Q/V