16. Capacitors (2026) notes NJC

National Junior College Science Department | Physics 1 16. Capacitors (Extension to the topic of “Electric fields” and “Current and Circuits”) Content Page Learning Objectives ...................................................................................................................... 1 16.1 Capacitance .......................................................................................................................... 2 16.1.1 Charging and discharging a capacitor ............................................................................ 3 16.1.2 The meaning of capacitance .......................................................................................... 4 16.1.3 Energy stored in a capacitor .......................................................................................... 5 16.1.4 Capacitance of isolated bodies ...................................................................................... 7 16.2 RC circuits ............................................................................................................................ 8 16.2.1 Capacitors in series and in parallel ................................................................................ 8 16.2.2 Sharing charge and energy .......................................................................................... 11 16.2.3 RC circuits with constant e.m.f. source ........................................................................ 13 16.3 Some applications of capacitors ......................................................................................... 17 Exercise 1 ................................................................................................................................... 19 LEARNING OBJECTIVES Capacitance (a) Define capacitance as the ratio of the charge stored to the potential difference and use C= QV to solve problems. (b) Recall that the electric potential energy stored in a capacitor is given by the area under the graph of potential difference against charge stored, and use this and the equations U= 12 QV, U= 12Q2C, and U= 12 CV2 to solve problems. RC circuits (c) Solve problems using the formulae for the combined capacitance of two or more capacitors in series and in parallel. (d) Describe and represent the variation with time, of quantities like current, charge and potential difference, for a capacitor that is charging or discharging through a resistor, using equations of the form x=x0e!t! or x=x0#1−e!t!%, where 𝜏= RC is the time constant.

National Junior College Science Department | Physics 2 16.1 CAPACITANCE (a) Define capacitance as the ratio of the charge stored to the potential difference and use C= QV to solve problems. (b) recall that the electric potential energy stored in a capacitor is given by the area under the graph of potential difference against charge stored, and use this and the equations U= 12 QV, U= 12Q2C, and U= 12 CV2 to solve problems. Most electronic devices