17.3 Capacitor With Dielectrics

 + dielectric ® V₀ decrease 

17.2 Charging & Discharging of capacitors

q Electrons will flow out from the negative terminal of the battery, through the resistor R and accumulate on the plate B of the capacitor.

q Then electrons will flow into the positive terminal of the battery, leaving a positive charge on the plate A.

q As charge accumulates on the capacitor, the potential difference across it increases and the current is reduced until eventually the maximum voltage across the capacitor equals the voltage supplied by the battery, Vo.

q At this time, no further current flows (I = 0) through the resistor R and the charge Q on the capacitor thus increases gradually and reaches a maximum value Qo

V₀ = V_R + V_C, V_R = IR, V_C = Q/C

At t = 0, V₀ = V_R, V_C = 0

During charging, V₀ = IR + Q/C, I in resistor decreasing, Q in capacitor increasing

As t ® ¥, V₀ = V_C, V_R = 0

•Initially, the potential difference (voltage) across the capacitor is maximum, V0 and then a maximum current I0 flows through the resistor R.

•When part of the positive charges on plate A is neutralized by the electrons, the voltage across the capacitor is reduced.

•The process continues until the current through the resistor is zero.

•At this moment, all the charges at plate A is fully neutralized and the voltage across the capacitor becomes zero.

V₀ = V_R + V_C, V_R = IR, V_C = Q/C

At t = 0, V₀ = V_C, V_R = 0

During discharging, V₀ = IR + Q/C, I in resistor decreasing, Q in capacitor decreasing

As t ® ¥, V₀ = V_R, V_C = 0

17.1 Capacitance & capacitors in series & parallel

17. CAPACITOR & DIELECTRICS

16.4 Charge In a Uniform Electric Field

Consider an electron (e) with mass, me enters a uniform electric field, E perpendicularly with an initial velocity u

Charge moving parallel to the field

Tutorial 16: Electrostatics

Click here: Tutorial 16, Sem II, KMS 2016

16.2 Electric Field

What?
It is a field or space around a charge particle where its force can be experienced by any other charge particle. Electric field is also known as electrostatic field intensity. If a charge is positive charge, then the lines of force come out of this charge. Again for a negative charge, these lines of force come into this charge.

What is the Direction of Electric Field?

Electrostatic force and electrostatic field both are vector quantity. As electric field is the force per unit test charge, so the direction of electrostatic field must follow the direction of electrostatic force. Again the direction of the electric field intensity is given by the direction of motion of the test charge.

16.1 Coulomb's Law

Main ideas:

1. The forces created between two charged objects

2. As distance increases, the forces and electric fields decrease

Need to understand that forces between objects become stronger as they move together and weaker as they move apart

SF026/ Topics (Themes)

Semester II, Sesi 2016/17

for Semester II, Sesi 2016/17