Electricity

• What must be true for electrical charge to flow?

  The circuit must be closed
• What is required for charge to flow in a circuit?

  There must be a source of potential difference
• What does electrical current represent?

  Current is the flow of electrical charge
• How does the rate of flow of charge relate to current?

  Greater flow rate means greater current
• What is the formula for charge flow?

  $Q =$$I \cdot t$
• What is true about current in a single closed loop?

  The current has the same value at any point
• What factors affect the current through a component?

  Resistance and potential difference affect current
• How does resistance affect current for a given potential difference?

  Greater resistance results in smaller current
• What is the equation relating potential difference, current, and resistance?

  $V =$$I \cdot R$
• What happens to current in an ohmic conductor?

  Current is directly proportional to potential difference
• What type of graph represents an ohmic conductor?

  The graph is linear
• How does the resistance of a filament lamp change?

  Resistance increases as temperature increases
• What is unique about the current through a diode?

  Current flows in one direction only
• How does current affect resistance in a resistor?

  As current increases, resistance increases
• What happens to electrons when they flow through a resistor?

  They collide with atoms, transferring energy
• How does temperature affect resistance in normal wires?

  Resistance increases as temperature increases
• What is the behavior of a thermistor at higher temperatures?

  Resistance is lower at higher temperatures
• How does the length of a wire affect resistance?

  Greater length results in greater resistance
• What happens to resistance in an LDR with increased light intensity?

  Resistance decreases with increased light intensity
• What is the function of the earth wire in a plug?

  It prevents the appliance from becoming live
• What is the frequency of mains electricity in the UK?

  50 Hz
• What is the voltage of the domestic electricity supply in the UK?

  About 230 V
• What is the difference between AC and DC?

  AC varies; DC flows in one direction
• What does power represent in an electrical context?

  Energy transferred per second
• How is power related to current and voltage?

  Power is directly proportional to current and voltage
• What is the formula for energy transferred in terms of power?

  $E =$$P \cdot t$
• What is the formula for energy transferred in terms of charge?

  $E =$$Q \cdot V$
• How is work done related to charge flow?

  Work done equals energy transferred
• What does the power rating of an appliance indicate?

  It shows the power used in Watts
• What are the characteristics of series circuits?

  • Closed circuit
  • Current follows a single path
  • Current is the same everywhere
  • Total resistance is the sum of individual resistances
• What are the characteristics of parallel circuits?

  • Branched circuit
  • Current splits into multiple paths
  • Total current into a junction equals total current in branches
  • Potential difference is the same across each branch
• How does total resistance behave in series and parallel circuits?

  • Series: Total resistance is the sum of resistances
  • Parallel: Total resistance is less than the smallest resistor
• What is the color of the live wire in a plug?

  Brown
• What is the color of the neutral wire in a plug?

  Blue
• What is the color of the earth wire in a plug?

  Green and yellow stripes
• What happens if the live wire touches the metal casing of an appliance?

  The appliance becomes live, causing shock risk
• How is energy transferred in everyday appliances?

  Through kinetic, thermal, or work done
• What is the relationship between power loss and current?

  Power loss is proportional to the square of the current
• What is the relationship between energy transferred and power?

  Energy transferred equals power times time
• What is the relationship between energy transferred and charge?

  Energy transferred equals charge times potential difference