An Introduction to Electricity

• Standard Circuit Symbols

  . In diagrams of electrical circuits:

  - standard circuit symbols are used to represent the components

  - wires should be drawn as straight lines using a ruler.
• What is this?

  Switch (closed)

  
• What is this?

  Cell

  
• What is this?

  Battery

  
• What is this?

  Diode

  
• What is this?

  Resistor

  
• What is this?

  Variable resistor

  
• What is this?

  LED (light emitting diode)

  
• What is this?

  Bulb/lamp

  
• What is this?

  Fuse

  
• What is this?

  Voltmeter

  
• What is this?

  Ammeter

  
• What is this?

  Thermistor

  
• What is this?

  LDR (light dependent resistor)

  
• Electric Charge and Current

  . Electric current is the flow of electrical charge - the greater the rate of flow, the higher the current.

  . Current is measured in amperes (A), which is often abbreviated to amps, using an ammeter.

  . Electric charge is measured in coulombs (C)

  . As the current in a single, closed loop of a circuit has nowhere else to go (i.e. no branches to travel down), the current is the same at all points in the loop.
• Key Point

  An ammeter is connected in series. A voltmeter is connected in parallel to the component.
• What does resistance measure in a component?

  How it resists the flow of charge
• What happens to charge flow when resistance is higher?

  It becomes more difficult for charge to flow
• How does higher resistance affect current?

  It results in lower current
• In what unit is resistance measured?

  Ohms
• What does potential difference indicate in a circuit?

  The difference in electrical potential between two points
• How can potential difference be described in terms of electrical force?

  As electrical push
• What happens to charge flow when potential difference increases?

  The flow of charge through the component increases
• How does increased potential difference affect current?

  It results in a bigger current
• In what unit is potential difference measured?

  Volts (V)
• What instrument is used to measure potential difference?

  Voltmeter
• What is the relationship between potential difference, current, and resistance?

  They are linked by the equation V=IR
• What is the equation that relates potential difference, current, and resistance?

  • V = IR
  • V: Potential difference
  • I: Current
  • R: Resistance
• Key Point

  . Increasing the resistance reduces the current.

  . Increasing the voltage increases the current.
• What is the purpose of the RQP sample method?

  To investigate factors affecting resistance
• How does the length of a wire affect its resistance?

  Longer wires generally have higher resistance
• What are the steps to investigate wire resistance based on length?

  1. Set up the standard test circuit.
  2. Pre-test and adjust supply voltage.
  3. Record voltage and current at various lengths.
  4. Use crocodile clips to grip wire.
  5. Maintain constant current with a variable resistor.
  6. Calculate resistance using voltage and current.
• What should be done before recording measurements in the circuit?

  Pre-test the circuit and adjust voltage
• Why is it important to adjust the supply voltage?

  To ensure measurable differences in readings
• What tool is used to grip the wire at different points?

  Crocodile clips
• What is the role of the variable resistor in the experiment?

  To keep current constant at each length
• How do you calculate resistance using voltage and current measurements?

  Resistance = Voltage / Current
• What is the formula for calculating resistance?

  Resistance = Voltage / Current
• What is the significance of measuring resistance in electrical circuits?

  It helps understand how materials conduct electricity
• How does maintaining a constant current affect the experiment's accuracy?

  It ensures consistent resistance measurements