Current, Potential Difference and Resistance

• What is the circuit symbol for a cell?

  Single long line and short line
• What is the circuit symbol for a battery?

  Two long lines and short lines
• What is the circuit symbol for a lamp?

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

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

  Circle with a 'V' inside
• What is the circuit symbol for an ammeter?

  Circle with an 'A' inside
• What is the circuit symbol for a diode?

  Triangle pointing to a line
• What is the circuit symbol for a resistor?

  Rectangle or zigzag line
• What is the circuit symbol for a thermistor?

  Rectangle with a zigzag line
• What is the circuit symbol for a variable resistor?

  Rectangle with an arrow across
• What is the circuit symbol for an LDR?

  Rectangle with a light symbol
• What is electric current?

  The flow of electrical charge
• What is the circuit symbol for an LED?

  Circle with two arrows pointing out
• 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, LDRs
• What happens to the resistance of a filament lamp as the temperature increases?

  Resistance increases due to more collisions
• Why does resistance increase in a filament lamp as temperature increases?

  Ions vibrate more, causing more collisions
• What is different about current flow through a diode?

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

  The thermistor’s resistance decreases
• Give two examples of when a thermistor may be used.

  In a thermostat and a freezer
• What happens to the resistance of an LDR as light intensity decreases?

  The LDR’s resistance increases
• Give an application for an LDR.

  Used in street lights
• What are the circuit symbols for common electrical components?

  • Cell: Single long line and short line
  • Battery: Two long lines and short lines
  • Lamp: Circle with a cross inside
  • Fuse: Rectangle with a line inside
  • Voltmeter: Circle with a 'V' inside
  • Ammeter: Circle with an 'A' inside
  • Diode: Triangle pointing to a line
  • Resistor: Rectangle or zigzag line
  • Thermistor: Rectangle with a zigzag line
  • Variable Resistor: Rectangle with an arrow across
  • LDR: Rectangle with a light symbol
  • LED: Circle with two arrows pointing out