electricity

• What must be true for electrical charge to flow in a circuit?

  The circuit must be closed and there must be a source of potential difference.
• What is electrical current?

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

  The greater the rate of flow of charge, the greater the current.
• What is the formula relating charge flow, current, and time?

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

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

  The current depends on both the resistance of the component and the potential difference across it.
• How does resistance affect current for a given potential difference?

  The greater the resistance, the smaller the current for a given potential difference.
• What is the equation that relates potential difference, current, and resistance?

  $V =$$I \cdot R$
• What characterizes an ohmic conductor?

  If the resistance is constant, current is directly proportional to the potential difference.
• How does the resistance of components like lamps and diodes change with current?

  The resistance changes with the current, resulting in a nonlinear graph.
• What happens to resistance as current increases in a resistor?

  Resistance increases as current increases due to energy transfer to atoms causing them to vibrate more.
• How does temperature affect resistance in normal wires?

  As temperature increases, resistance increases due to increased atomic vibrations.
• What is the behavior of a thermistor with temperature changes?

  In hotter temperatures, the resistance of a thermistor is lower.
• How does the length of a wire affect its resistance?

  The greater the length, the more resistance and the lower the current.
• What is the relationship between light intensity and resistance in an LDR?

  The greater the intensity of light, the lower the resistance in an LDR.
• What happens to the resistance of a diode in the reverse direction?

  A diode has a very high resistance in the reverse direction, preventing current flow.
• What is the total resistance in a series circuit?

  Total resistance is the sum of the resistance in each component.
• How does current behave in a series circuit?

  The current is the same everywhere in a series circuit.
• What is true about potential difference in a series circuit?

  The potential difference of the power supply is the sum of the potential difference across each component.
• What characterizes a parallel circuit?

  In a parallel circuit, current splits into multiple paths.
• How does potential difference behave in a parallel circuit?

  The potential difference is the same across each branch in a parallel circuit.
• What is the relationship between total current and branches in a parallel circuit?

  The total current into a junction equals the total current in each of the branches.
• What is the mains electricity supply in the UK?

  Mains electricity is an AC supply with a frequency of 50 Hz and about 230 V.
• What is the difference between AC and DC?

  AC is alternating current, which continuously varies, while DC is direct current, moving in one direction only.
• What are the three wires in a plug?

  Live wire, neutral wire, and earth wire.
• What is the function of the live wire in a plug?

  The live wire carries the alternating potential difference from the supply.
• What is the purpose of the earth wire?

  The earth wire is a safety wire that carries current only if there is a fault.
• How does power relate 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 and potential difference?

  $E =$$Q \cdot V$
• What is the National Grid?

  The National Grid is a system of cables and transformers linking power stations to consumers across the UK.
• What is the function of transformers in the National Grid?

  Transformers change the potential difference for efficient power transfer.
• What do step-up transformers do?

  Step-up transformers increase the potential difference from the power station to the National Grid.
• What is charge in terms of matter?

  Charge is a property of all matter, with positive and negative charges existing.
• What happens when a body has equal positive and negative charges?

  They cancel out, forming a neutral body.
• What do step-down transformers do?

  Step-down transformers decrease the potential difference from the National Grid to consumers.
• What is the behavior of like and opposite charges?

  Like charges repel, while opposite charges attract.
• What characterizes insulators and conductors?

  Insulators do not conduct electricity, while conductors can conduct electricity.
• What occurs when two insulators are rubbed together?

  Electrons are transferred, forming a positive charge on one object and a negative charge on the other.
• What happens when conductors are rubbed together?

  Electrons flow in and out, cancelling out any charge effect, so they stay neutral.