Electricity + D.C. Circuits
Table of Content
Current & Charge...................................................................................................................................... 1
Mean Drift Velocity................................................................................................................................. 2
Voltage............................................................................................................................................................ 3
Resistance & Ohm’s Law..................................................................................................................... 5
Power + Kirchoff’s Law.......................................................................................................................... 6
Internal Resistance + Potential Dividers....................................................................................8
Circuit Symbols....................................................................................................................................... 10
Current & Charge
+ Battery doesn’t produce electrons
→ Wires have delocalised electrons due to being a metallic lattice
→ Battery adds more electrons
1
, + Even without a battery, electrons still move at a slow speed
Electron flow: Movement of electrons - from negative to positive terminal
Conventional Flow: Movement of current/Flow of positive charges - from positive
to negative terminal
Current [Unit: Amperes (A)]: Rate of flow of charge carriers - Charge passing
through circuit per unit time
→ The higher the current, the higher the speed of flow
→ Measured using an Ammeter in series
Charge:
Q=I ×t
Note: Electric charge can be positive or negative
→ Coulomb [Physical Quantity]: 1C = Quantity of charge that passes a point per
second when the current is 1A
+ Current moves from high potential area to low potential area = work is
being done - requires electric potential energy
Electric Potential Energy: Energy needed to move a charge against an electric
field
Calculating No. of Charge Carriers (n):
Total Charge( C)
−19
=No . of charge carriers
Elementary Charge(1.6 × 10 C )
Mean Drift Velocity
→ How to calculate current without an Ammeter
2
Table of Content
Current & Charge...................................................................................................................................... 1
Mean Drift Velocity................................................................................................................................. 2
Voltage............................................................................................................................................................ 3
Resistance & Ohm’s Law..................................................................................................................... 5
Power + Kirchoff’s Law.......................................................................................................................... 6
Internal Resistance + Potential Dividers....................................................................................8
Circuit Symbols....................................................................................................................................... 10
Current & Charge
+ Battery doesn’t produce electrons
→ Wires have delocalised electrons due to being a metallic lattice
→ Battery adds more electrons
1
, + Even without a battery, electrons still move at a slow speed
Electron flow: Movement of electrons - from negative to positive terminal
Conventional Flow: Movement of current/Flow of positive charges - from positive
to negative terminal
Current [Unit: Amperes (A)]: Rate of flow of charge carriers - Charge passing
through circuit per unit time
→ The higher the current, the higher the speed of flow
→ Measured using an Ammeter in series
Charge:
Q=I ×t
Note: Electric charge can be positive or negative
→ Coulomb [Physical Quantity]: 1C = Quantity of charge that passes a point per
second when the current is 1A
+ Current moves from high potential area to low potential area = work is
being done - requires electric potential energy
Electric Potential Energy: Energy needed to move a charge against an electric
field
Calculating No. of Charge Carriers (n):
Total Charge( C)
−19
=No . of charge carriers
Elementary Charge(1.6 × 10 C )
Mean Drift Velocity
→ How to calculate current without an Ammeter
2
