Practical electrical and electronic circuits

• Current is measured using an ammeter
• An ammeter is connected in series with a component
• Voltage is measured using a voltmeter
• A voltmeter is used across a component
• Resistance is measured using an ohmmeter
• An ohmmeter is connected in parallel without a supply voltage
• When adding further resistors in series, the total resistance increases.
• When adding further resistors in parallel, the total resistance decreases
• A thermistor changes resistance with changing temperature
• As the temperature increases, the resistance of and voltage across the thermistor decreases
• A LDR changes resistance with light level
• As the light level increases, the resistance of and voltage across the LDR decreases
• The function of transistors (npn and MOSFET) is as an electric switch
• A npn-transistor will switch on at 0.7V
• A MOSFET will switch on at around 2V
• A relay connects a low voltage circuit to a high voltage circuit
• A diode conducts electricity in one direction only
• An LED is a diode that emits light
• A resistor is connected in series with a diode to protect the diode from

  • too high of a current through it
  • too high of a voltage across it
• Factors which affect the resistance of a wire:

  • material - copper has a lower resistance than brass
  • length - the longer the wire the greater the resistance
  • thickness - thin wires have a greater resistance than thick wires
  • temperature - heating a wire increases its resistance