Electrons, waves and photons

Electrons, waves and photons

1. Electric Current

   • The electric current is the rate of flow of charge in a wire or component.
     • unit is the ampere (A)
       • In liquids & gases, the charge carriers are ions.
     • Due to the passage of charge particles, referred to as charge carriers.
       • In metals, the charge carriers are electrons.
   • Charge
     • The unit of charge is the coulomb (C), which is defined as the charge flow in one second when the current is one ampere.
     • The symbol for charge is Q.
     • The charge of an electron is e=1.6 × 10-19 C
   • ΔQ = IΔt

2. Resistance

   • Electromotive Force (e.m.f) is the energy transferred per unit charge when one other type of energy is converted into electrical energy.
     • Potential difference (p.d) is the electrical energy transferred per unit charge when electrical energy is converted into another form
       • P = VI = I^2R = V^2/R
   • Ohm's Law states that the current through a conductor is proportional to the p.d across it.
   • Resistivity is the resistance that a material naturally has.
     • Resistivity = (resistance*area)/wire length
   • A Kilowatt-hour (kWh) is 1000 Watts for 3600 seconds = 3,600,000 J

3. DC circuits

   • In a series circuit,