Current and circuits

• What is current in an electrical circuit?

  Flow of electrical charge
• What does the total charge through a circuit depend on?

  Current and time
• What are the circuit symbols you should know?

  • Resistor
  • Battery
  • Ammeter
  • Voltmeter
  • Diode
• What happens to charges as they flow around a circuit?

  They transfer energy against resistance
• What is potential difference defined as?

  Energy transferred per unit charge
• How do you calculate energy transferred in joules?

  Using the formula E = Q × V
• What does one coulomb of charge passing through one volt represent?

  One joule of energy transferred
• What is another term for potential difference?

  Voltage
• What is the formula relating potential difference, current, and resistance?

  V = I × R
• How can you rearrange the formula V = I × R to find current?

  I = V ÷ R
• If a 40 Ω resistor has a potential difference of 60 V, what is the current?

  I = 1.5 A
• How does resistance affect current in a circuit?

  Higher resistance decreases current
• What happens to a resistor when current flows through it?

  It heats up due to energy transfer
• Why does resistance usually increase with temperature?

  Electrons collide more with vibrating ions
• What happens if a resistor gets too hot?

  No current will flow
• What is a thermistor?

  A temperature-dependent resistor
• How does the resistance of a thermistor change with temperature?

  Resistance decreases as temperature increases
• What is the standard test circuit used for?

  • Investigating current (I), potential difference (V), and resistance
  • Measuring components like filament lamps and resistors
  • Plotting I-V graphs
• What does an ammeter measure?

  Current in amps
• Where must an ammeter be placed in a circuit?

  In series with the component
• What does a voltmeter measure?

  Potential difference across a component
• Where must a voltmeter be placed in a circuit?

  In parallel with the component
• What should you do if the circuit gets too hot during an experiment?

  Disconnect it to cool down
• What is the relationship between current and potential difference in linear components?

  Current is directly proportional to voltage
• What characterizes non-linear components in I-V graphs?

  They have curved I-V graphs
• How can you find the resistance from an I-V graph?

  Using V = IR at any point
• How does light intensity affect the resistance of an LDR?

  Resistance falls in bright light
• What does LDR stand for?

  Light Dependent Resistor
• What is a thermistor's behavior in hot conditions?

  Resistance drops in hot conditions
• What happens to current when resistors are added in series?

  Current is reduced through each resistor
• What is the effect of adding resistors in series?

  Total resistance increases
• What is the total resistance of two resistors in parallel?

  Less than the smallest resistor
• How does adding resistors in parallel affect total current?

  Increases total current flow
• What are the key differences between series and parallel circuits?

  • Series circuits: All components share the same current; total resistance increases.
  • Parallel circuits: Each component operates independently; total resistance decreases.
• What happens to the current when a resistor is added in series?

  The current is reduced in each resistor.
• How does adding a resistor affect the total resistance in a series circuit?

  Total resistance increases in the circuit.
• What is the relationship between a component's resistance and its share of potential difference?

  Bigger resistance means bigger share of p.d.
• What happens to total resistance when two resistors are connected in parallel?

  Total resistance is less than the smallest resistor.
• Why do resistors in parallel have the same potential difference across them?

  They share the same source p.d.
• How does adding another loop in a parallel circuit affect current flow?

  It increases the total current in the circuit.