Electricity and Circuits

• What is the purpose of the standard test circuit?

  To investigate current, p.d., and resistance
• What components are included in the standard test circuit?

  An ammeter, voltmeter, and variable resistor
• How does increasing resistance affect current in the circuit?

  It lowers the current through the circuit
• What are the steps to investigate a component using the standard test circuit?

  1. Connect the circuit as shown.
  2. Change the variable resistor's resistance.
  3. Measure current and p.d. across the component.
  4. Take multiple readings at different resistances.
  5. Plot I-V graphs from the data.
  6. Ensure the circuit doesn't overheat.
  7. Repeat and calculate means.
• What happens to current when the diode's direction is swapped?

  Current cannot flow through the diode
• How does temperature affect the resistance of a thermistor?

  Resistance decreases as temperature increases
• What is the behavior of an LDR in bright light?

  Its resistance falls in bright light
• What are the characteristics of linear and non-linear components in I-V graphs?

  • Linear components: straight line (e.g., fixed resistor)
  • Non-linear components: curved line (e.g., filament lamp, diode)
  • Current is directly proportional to p.d. for linear components.
• What does an LDR stand for?

  Light Dependent Resistor
• How does the resistance of a thermistor change with temperature?

  Resistance decreases as temperature increases
• What are the rules for series circuits?

  1. Components connected end to end.
  2. Current is the same everywhere.
  3. Total p.d. is shared among components.
  4. Total resistance is the sum of individual resistances.
• What are the rules for parallel circuits?

  1. Each component is separately connected.
  2. Removing one component doesn't affect others.
  3. Potential difference is the same across all components.
  4. Total current is the sum of currents through each branch.
• How does adding resistors in series affect total resistance?

  Total resistance increases with added resistors
• What happens to total resistance when resistors are added in parallel?

  Total resistance decreases with added resistors
• What is the equation for energy transferred in a circuit?

  E = I x V x t

  • E: energy in joules (J)
  • I: current in amps (A)
  • V: potential difference in volts (V)
  • t: time in seconds (s)
• How does the power of an appliance relate to energy transfer?

  Power is energy transferred per second
• What is the formula for calculating power?

  P = E ÷ t
• How does a higher power rating affect cooking time in microwaves?

  Higher power cooks food faster
• What is Ohm's Law?

  I = V ÷ R
• Why is it important to take multiple readings in experiments?

  To ensure accuracy and reliability of results
• What role do fuses play in electrical circuits?

  They protect circuits by melting at high currents
• How does energy transfer affect the efficiency of electrical devices?

  Higher energy transfer reduces efficiency
• What does the total energy transferred by an appliance depend on?

  Time the appliance is on and its power
• How is the power of an appliance defined?

  Energy transferred per second
• What is the formula to calculate power of an appliance?

  Power (W) = Energy (J) ÷ Time (s)
• What does a power rating indicate for an appliance?

  Maximum safe power it can operate at
• Why does a microwave with a lower power rating take longer to cook food?

  It transfers less energy per second
• How does a lower power rating affect electricity usage?

  Less electricity used in a given time
• Can a higher power rating guarantee more useful energy transfer?

  No, it may be less efficient
• What two factors affect the power transferred by an appliance?

  Potential difference and current
• What does potential difference indicate in an electrical circuit?

  Energy each unit of charge transfers
• What is the formula for electrical power?

  Power (W) = Current (A) × Potential difference (V)
• How do you calculate the current used by a 1 kW hair dryer on a 230 V supply?

  Current = 1000 ÷ 230 = 4.3 A
• What happens if the live wire touches the metal case of an appliance?

  A surge in current can occur
• What is the purpose of the earth wire?

  To carry current away for safety
• What is the potential difference between the live and neutral wires?

  230 V for mains supply
• What happens when you touch the live wire?

  A large potential difference is produced
• Why is there still a danger of electric shock even when a switch is off?

  There is still a p.d. in the live wire
• What can happen if there is a connection between live and neutral wires?

  A huge current can flow, causing fire
• What are the two types of electricity supply?

  Alternating current (a.c.) and direct current (d.c.)