Electricity

• What is voltage also known as?

  Potential difference
• How is voltage defined?

  Energy transferred to each coulomb of charge
• In what unit is voltage measured?

  Volts (V)
• What is the relationship between volts and joules per coulomb?

  1 V = 1 J per C
• What is current defined as?

  Charge transferred per second
• How is current measured?

  In amps (A)
• What is the mains voltage and frequency?

  230V, 50 Hz
• What factors increase resistance in a wire?

  • Temperature
  • Length of wire
  • Thickness of wire
• What does A.C. stand for?

  Alternating current
• How does A.C. differ from D.C.?

  A.C. changes direction; D.C. does not
• What does D.C. stand for?

  Direct current
• What is Ohm's Law?

  V = I × R
• What is the gradient of an Ohm's Law graph?

  Gradient, m = V / I = R
• What are the rules for series circuits?

  • Is = I1 = I2…
  • Vs = V1 + V2…
  • RT = R1 + R2…
• What are the rules for parallel circuits?

  • Is = I1 + I2…
  • Vs = V1 = V2…
  • 1/RT = 1/R1 + 1/R2…
• How are ammeters connected in a circuit?

  In series
• How are voltmeters connected in a circuit?

  In parallel

  
• How are ohmmeters connected in a circuit?

  No power supply
• What is the function of a transistor?

  Acts as an electronic switch
• What input voltage is needed for an npn transistor to switch on?

  0.7V or above
• What input voltage is needed for an n-channel enhancement MOSFET to switch on?

  2V or above
• What are output devices in electronics?

  • Change electrical energy into another form
  • Examples include LEDs, motors, etc.

  
• What are input devices in electronics?

  • Change another form of energy into electrical energy
  • Examples include sensors, switches, etc.
• What is the role of a series resistor with an LED?

  • Protects LED from high current
  • Ensures proper functioning of the LED
• How do you calculate the resistance (R) for an LED circuit?

  R = VR / I
• What happens in a high light sensor circuit?

  Transistor switches ON, LED switches ON
• What happens in a low light sensor circuit?

  Transistor switches ON, LED switches ON
• What happens in a low temperature switch circuit?

  Transistor switches ON, LED switches ON
• What happens in a high temperature switch circuit?

  Transistor switches ON, LED switches ON
• What are voltage dividers?

  • Divide a supply voltage between 2 resistors
  • Used in various electronic applications
• How is power defined in electrical terms?

  Energy transferred per second
• In what unit is power measured?

  Watts (W)
• What is the relationship between watts and joules per second?

  1 W = 1 J per s
• What is the formula for energy supplied to charges?

  Ew = Q × V
• What happens to a fuse when the current is too high?

  It melts to break the circuit
• What fuse rating is required for appliances under 720W?

  3A fuse
• What fuse rating is required for appliances above 720W?

  13A fuse
• Why do some appliances under 720W require a 13A fuse?

  They have a high current on switch on
• What is the relationship between current, voltage, and power?

  • Power = current × voltage
  • Power = current² × resistance
  • Power = voltage² / resistance
• How does current and voltage affect power developed?

  Greater current/voltage = greater power