electricity

• what is electrical current?

  the rate of flow of charge
• what is the equation that links charge, current and time?

  Q= I x t
• equation that links potential difference, current and resistance

  v = I X R
• What is the difference between a series and a parallel circuit?

  A series circuit has one path for current to flow, while a parallel circuit has multiple paths.
• what does ohm's law say?

  current through a ohmic conductor is directly proportional to the potential difference across the resistor
• what happens to the resistance of a filament lamp as the temperature increases?

  resistance increases
• what happens to the resistance of a thermistor as it increases in temperature?

  resistance decreases as the temperature increases
• what happens to the resistance of a LDR as the light intensity increases?

  resistance decreases
• what is special about the way current flows through a diode?

  current can only flow one way through a diode
• name a application of an LDR/thermistor

  in sensing circuits
• how does resistance add in series?

  R=R1+R2
• what happens to current in series/parallel circuits?

  current is the same everwhere in series and spilts in parallel
• what happens to potential difference in series/parallel?

  series splits across components and in parallel is the same on different parts
• what happens to the total resistance of two resistors in parallel?

  the total resistance is less than the resistance of the smallest resistor
• what is used to measure potential difference/current?

  Voltmeter/Ameter
• what is the frequency and potential difference of the mains electricity supply?

  50 Hz and 230 V
• what is the difference between AC and DC?

  alternate current changes direction, Direct current remains in same direction
• what are the colours of plug wires?

  live-brown, neutral-blue, earth-green and yellow stripes
• what happens to the fuse if the current is too high?

  the fuse melts, making the circuit incomplete and stops current from flowing
• two equations for electrical power

  P = V X I P=I X I X R
• Two equations for energy transfer


  E= P X T E = Q X V
• What do step-up transformers do?

  it increases the potential difference, but decreases the current to reduce heat loss in cables
• what do step-down transformers do?

  it decreases the potential difference to a safe level for consumers