Lesson Two

Lesson Two

1. Electric current (E.C) is the flow of electric charge (E.ch) in free electrons form

   • E.C of one ampere (A) flows in a circuit when a charge of one coulomb passes a point in 1/s.
     • Constant current: I Time-varying current: i

2. Conventional current flow - From positive (+) to negative (-)

   • Alternating current (AC), interchanges between a positive and negative direction with time. Direct current (DC), is current that is fixed in a constant direction.
     • Mathematically, I (A) = Q (C)/t(s)

3. Ability of a charged particle to do work is an electric potential. Two unlike charges - Difference of potential.

   • P.D between two points is one V if one J of work is done displacing one C of charge. The SI unit of potential difference is the volt (V).

4. P.D referred to as voltage (V) A constant voltage called a DC voltage. AC voltage alternates with time

   • potential difference is given as: V (volts) = W (joules) / Q (coulombs).

5. Resistance is opposite to current flowing around an electrical circuit.

   • Resistors are passive devices.
     • The SI unit of resistance: Ohm

6. Length of the material: Resistance of a material is directly proportional to its length. The longer the material the more resistance it has.

   • Cross-sectional area: Resistance of a material is indirectly proportional to its area. The thicker the material is the less resistance it has.

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