Electricity and circuits

• What is the definition of current in physics?

  Flow of electric charge
• How is current compared to the flow of water?

  Current is like water flow in a pipe
• What is the unit of potential difference?

  Volt, V
• What does resistance do in a circuit?

  Slows down the flow of current
• What is the unit of resistance?

  Ohm, Ω
• How does current depend on potential difference and resistance?

  Current depends on voltage and resistance
• What happens to current with higher potential difference?

  Higher potential difference increases current
• What effect does higher resistance have on current?

  Higher resistance decreases current flow
• What is the formula for charge in a circuit?

  Q = I × t
• What units are used for current, time, and charge in the formula Q = I × t?

  Amperes, seconds, and coulombs
• How much charge passes through a circuit with a current of 0.25 A over 4 hours?

  3600 C
• What is the energy transferred formula in terms of charge and potential difference?

  E = Q × V
• What is the relationship between resistance, potential difference, and current?

  V = I × R
• How does resistance change with temperature?

  Resistance usually increases with temperature
• How do you calculate potential difference if 300 J of energy is transferred with 75 C of charge?

  Potential difference = 4 V
• What is the resistance of a resistor with a potential difference of 4.25 V and a current of 0.25 A?

  Resistance = 17 Ω
• What is the purpose of the standard test circuit in experiments?

  • Investigate relationship between current (I) and voltage (V)
  • Use ammeter to measure current
  • Use voltmeter to measure potential difference
• What are the steps to investigate a component in a circuit?

  1. Connect the component under test
  2. Change current and record data
  3. Measure current (I) and voltage (V)
  4. Take multiple readings
  5. Plot potential difference
  6. Calculate resistance using R = V/I
• What are the characteristics of thermistors?

  • Resistance changes with temperature
  • High resistance in cool conditions
  • Low resistance in hot conditions
• What are the characteristics of LDRs?

  • Light Dependent Resistors
  • Resistance decreases as light increases
  • Used in light-sensitive applications
• What is the function of an ammeter in a circuit?

  Measures current in circuits
• How should ammeters and voltmeters be connected in a circuit?

  Ammeter in series, voltmeter in parallel
• What happens to the resistance of a thermistor as temperature increases?

  Resistance decreases as temperature increases
• What is one everyday use for an LDR?

  Automatic street lights
• What are the three important graphs related to electricity and circuits?

  1. Current vs. Voltage for resistors
  2. Current vs. Voltage for thermistors
  3. Current vs. Voltage for LDRs
• What happens to current in series circuits?

  The current is the same everywhere
• Why is the total potential difference greater in series circuits?

  More cells connected increases total p.d.
• If two batteries of 1.5 V are connected in series, what is the total p.d.?

  3 V
• How does the total resistance change when resistors are added in series?

  Total resistance increases with added resistors
• How are components connected in parallel circuits?

  Each component is separately connected
• What happens if one component is removed from a parallel circuit?

  It hardly affects the others
• What is the relationship between potential difference and current in parallel circuits?

  Potential difference is the same across all components
• Why are parallel circuits used in household electrics?

  To switch devices on and off separately
• How is current shared in parallel circuits?

  Current is shared between branches
• What must be true about current at a junction in a parallel circuit?

  Total current entering equals total current leaving
• What happens to total resistance when a second resistor is added in parallel?

  Total resistance decreases
• What is the effect of increasing potential difference in a series circuit?

  Current through the resistor increases
• What is the relationship between p.d. and current in a filament bulb?

  It shows a non-linear relationship
• How does the total current in a parallel circuit compare to the current in a series circuit?

  Total current in parallel is greater
• What is the formula for calculating power in circuits?

  Power = Energy transferred ÷ Time