Current Electricity

Current Electricity

1. Potential Difference

   • A.K.A Voltage
   • Volt
   • Scalar quantity
   • V = W/Q
     • W = work
     • Q = charge
   • Electromotive force (emf)
     • A voltage that is applied to a circuit

2. Capacitance

   • Electrical device that stores electric charge
   • C = εA/d
     • ε = permittivity
     • A = common area
     • d = distance between plates
   • Energy stored in a capacitor
     • W = (1/2)CV²
   • Capacitors conduct A.C. but not D.C.

3. Electric current (I)

   • Flow of electric charge
   • Scalar quantity
   • Ampere (A)
   • Q = It
     • Q = charge
     • I = current
     • t = time
   • Ammeter
   • Effects
     • Chemical
     • Magnetic
     • Heating
   • Joule's Law
     • P = I²R
       • P = power
       • I = current
       • R = resistance

4. Domestic circuits

   • Plugs
     • Live wire
     • Neutral wire
     • Earth wire
     • Two-pin plugs
       • Do not need to be earthed
   • Fuses
     • Wire that will melt when current above a certain size passes through it
   • Miniature circuit breakers
     • Prevent electrocution or fire
   • Residual current devices

5. kilowatt-hour (kWh)

   • Energy (in kWh) = Power (in kW) x time (in h)
   • Amount of energy used by a 1,000 watt appliance in one hour