Current, Potential difference and Resistance

• What is electric current defined as?

  The rate of flow of electric charge
• In what units is current measured?

  Amperes or amps (A)
• What does 1 amp represent in terms of charge and time?

  1 coulomb flowing in 1 second
• How is the size of an electric current defined?

  By the amount of charge passing through a component each second
• When does current flow in a circuit?

  When a circuit is formed
• In which direction does charge flow in a circuit?

  From the positive terminal to the negative terminal
• How can current be measured?

  Using an ammeter
• How must ammeters be connected in a circuit?

  In series with the component being measured
• What happens to electrons when a voltage is applied?

  They flow through the lattice of metal ions
• What is the flow of current in metal wires?

  A flow of negatively charged electrons
• What is conventional current?

  The flow of positive charge from positive to negative terminal
• Why is conventional current defined in the opposite direction to electron flow?

  Because scientists defined it before discovering the electron
• What is the equation relating current, charge, and time?

  Q = I × t
• What does the variable Q represent in the equation Q = I × t?

  Charge, measured in coulombs (C)
• How can the current, charge, and time equation be rearranged?

  Using a formula triangle
• When will 8 A of current pass through an electrical circuit?

  When a charge of 4 C passes in 0.5 s
• What is voltage defined as?

  The energy transferred per unit charge passing between two points
• In what units is voltage measured?

  Volts (V)
• What does 1 volt represent in terms of energy and charge?

  The transfer of 1 joule of energy by 1 coulomb of charge
• What happens to electrons as they flow through a cell?

  They gain energy
• What happens to electrons after leaving a cell?

  They transfer energy to the wires and components in the circuit
• How can voltage be measured?

  Using a voltmeter
• How must voltmeters be connected in a circuit?

  In parallel with the component being measured
• What is the equation linking energy transferred, voltage, and charge?

  E = Q × V
• What does the variable E represent in the equation E = Q × V?

  Energy transferred, measured in joules (J)
• How much energy is transferred in a lamp with a voltage of 6 V when 4200 C of charge flows through it?

  25,200 J
• What is resistance defined as?

  The opposition of a component to the flow of electric current
• In what units is resistance measured?

  Ohms (Ω)
• What does a resistance of 1 Ω indicate in terms of voltage and current?

  A voltage of 1 V produces a current of 1 A through it
• How does resistance affect current in a circuit?

  The higher the resistance, the lower the current that can flow
• What is the relationship between resistance and current for a given voltage?

  The lower the resistance, the higher the current that can flow
• What is a common material used for wires due to its low electrical resistance?

  Copper
• How does greater resistance affect current?

  It results in a lower current
• What is the equation relating voltage, current, and resistance?

  V = I × R
• What is the voltage across a resistor of resistance 10 Ω with a current of 0.3 A through it?

  3 V
• What is assumed about the resistance of wires, batteries, ammeters, and voltmeters in exam questions?

  They are assumed to be zero
• Why do voltmeters have extremely high resistances?

  To prevent current from flowing through them