electricity

• What is electric current?

  Electric current is a flow of electrical charge.
• What is required for electrical charge to move around a circuit?

  A complete (closed) circuit and a potential difference are required.
• What is the unit of current?

  The unit of current is the ampere, A.
• How does current behave in a simple closed loop circuit?

  The current has the same value everywhere in the circuit.
• What is potential difference and its unit?

  Potential difference is the driving force that pushes charge around a circuit, measured in volts (V).
• What factors affect the current flowing through a component?

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

  The greater the resistance, the smaller the current that flows.
• What is the formula linking potential difference and current?

  The formula is $V =$$I \times R$.
• What does an ammeter measure?

  An ammeter measures the current flowing through a test wire in amps.
• How should an ammeter be connected in a circuit?

  An ammeter must always be placed in series with whatever you're investigating.
• What does a voltmeter measure?

  A voltmeter measures the potential difference across a test wire in volts.
• How should a voltmeter be connected in a circuit?

  A voltmeter must always be placed in parallel across whatever you're investigating.
• What is the procedure to investigate the effect of wire length on resistance?

  1. Attach crocodile clips to the wire at specified lengths.
  2. Close the switch and record current and potential difference.
  3. Open the switch and adjust the clips for new lengths.
  4. Repeat for various lengths.
  5. Calculate resistance using $V =$$IR$.
  6. Plot resistance against wire length.
• What happens to the total potential difference in a series circuit?

  The total potential difference is shared between the various components.
• How does current behave in series circuits?

  The same current flows through all components in a series circuit.
• How is the total resistance in a series circuit calculated?

  The total resistance is the sum of the individual resistances: $R_{total} =$$R_1 +$$R_2$.
• If a circuit has a total resistance of 5 Ω and a potential difference of 20 V, what is the current?

  The current is $I =$$\frac{20 \text{ V}}{5 \text{ Ω}} =$$4 \text{ A}$.
• What happens to the potential difference across each resistor in a series circuit?

  The potential difference across each resistor is less than the total potential difference.
• How does adding more cells in series affect potential difference?

  More cells in series increase the total potential difference.
• What is the main advantage of parallel circuits over series circuits?

  Parallel circuits allow components to be independently connected, so removing one does not affect the others.
• What is the potential difference across components in a parallel circuit?

  The potential difference is the same across all components in a parallel circuit.
• How is current distributed in a parallel circuit?

  The total current is equal to the sum of the currents through the separate components.
• What happens to total resistance when resistors are added in parallel?

  The total resistance decreases when resistors are added in parallel.
• What are the characteristics of series circuits?

  • Components connected in a line
  • Same current flows through all components
  • Total potential difference is shared
  • Total resistance is the sum of individual resistances
• What are the characteristics of parallel circuits?

  • Components connected independently
  • Same potential difference across all components
  • Total current is the sum of individual currents
  • Adding resistors decreases total resistance
• What is the potential difference of a battery connected in series with a 4 Ω resistor and a 2 Ω resistor with a current of 0.5 A flowing through the circuit?

  The potential difference is $V =$$I \times R_{total} =$$0.5 \text{ A} \times (4 + 2) \text{ Ω} =$$3 \text{ V}$.
• What is the significance of having circuits wired in parallel in household electrics?

  • Allows independent operation of appliances
  • If one appliance fails, others continue to work
  • Provides consistent voltage across all devices