1.2 Electricity

• What is the circuit symbol for a lamp?

  Circle with a cross inside
• What is the circuit symbol for a battery?

  Two parallel lines, one longer
• What is the circuit symbol for a fuse?

  A rectangle with a line inside
• What is the circuit symbol for a voltmeter?

  Letter V
• What is the circuit symbol for an ammeter?

  Letter A
• What is the circuit symbol for a resistor?

  A zigzag line
• What is the circuit symbol for a diode?

  A triangle pointing to a line
• What is the circuit symbol for a thermistor?

  A resistor symbol with a temperature indicator
• What is the circuit symbol for a variable resistor?

  A zigzag line with an arrow
• What is the circuit symbol for an LDR?

  A rectangle with a light symbol
• What is the circuit symbol for an LED?

  A diode symbol with arrows
• What is electric current?

  The flow of electrical charge
• What is the equation linking charge, current, and time?

  Q = I t
• What are the units for charge, current, and time?

  Coulombs, Amperes, Seconds
• What can be said about the value of current at any point in a single closed loop?

  Current is the same at all points
• What two factors does the current in a circuit depend on?

  Potential Difference and Resistance
• What equation should be used to calculate potential difference if current and resistance are known?

  V = I R
• What are the units for potential difference, current, and resistance?

  Volts, Amperes, Ohms
• What is an ‘Ohmic Conductor’?

  Current and potential difference are proportional
• What condition is required for an ‘Ohmic Conductor’?

  Temperature must be constant
• List four components for which resistance is not constant as current changes.

  • Lamps
  • Diodes
  • Thermistors
  • Light Dependant Resistors (LDRs)
• What happens to the resistance of a filament lamp as the temperature increases?

  Resistance increases due to more collisions
• What is different about current flow through a diode?

  Current flows in one direction only
• What happens to the resistance of a thermistor as temperature increases?

  The thermistor’s resistance decreases
• What are the two ways to connect a component in a circuit?

  Series and parallel
• What happens to the resistance of an LDR as light intensity decreases?

  The LDR’s resistance increases
• How does potential difference vary in series and parallel circuits?

  • Series: Total P.D is shared
  • Parallel: P.D across each component is the same
• Give an application for an LDR.

  Used in street lights to detect light
• What can be said about the total resistance of two resistors connected in parallel?

  It is less than the smallest individual resistance
• What can be said about the total resistance of two resistors connected in series?

  It is equal to the sum of the two individual resistances
• How is the current described in a series circuit?

  The current is the same at all positions
• How is the current described in a parallel circuit?

  The current is shared between different branches
• How should an ammeter be connected in a circuit?

  In series with the component being measured
• How should a voltmeter be connected in a circuit?

  In parallel to the component being measured
• Why is it advantageous to connect lamps in parallel?

  Other lamps remain unaffected if one blows
• Is mains electricity an a.c supply or a d.c supply?

  a.c supply
• What does a.c. stand for?

  Alternating Current
• What does d.c. stand for?

  Direct Current
• What is alternating current?

  Current that continuously changes direction
• What is direct current?

  One directional current flow