Circuits

• What is electricity defined as?

  The flow of charge or charges
• What do electrons carry in an electrical circuit?

  Energy from a source to a component
• What is a simple circuit composed of?

  • A cell (or battery)
  • Wires
  • A lamp (light bulb)
• What is the symbol for a battery?

  Several cells connected in line
• Why must circuits have complete loops?

  To allow charges to flow continuously
• What type of energy does a battery store?

  Chemical potential energy
• What happens to electrons when connected in a complete circuit?

  They move through the wires carrying energy
• What is the term for the movement of charge in a circuit?

  Current
• From which terminal do electrons flow in a circuit?

  From the positive terminal to the negative
• What happens to the energy of electrons as they pass through a bulb?

  It is converted into light and heat
• What do electrons do after transferring energy to the bulb?

  They return to the battery for recharging
• What unit is used to measure charge?

  Coulombs (C)
• What does potential difference (PD) indicate?

  Energy transferred per coulomb of electrons
• What does a 1-volt battery supply?

  1 joule per coulomb of electrons
• How is PD measured in a circuit?

  With a voltmeter connected in parallel
• What should a voltmeter read when placed across a battery supplying 6 volts?

  6 volts
• What happens to the voltage when measured across a bulb in a circuit?

  It should still read 6 volts
• What does a negative voltage reading indicate?

  Electrons have lost energy passing through
• What is the equation for potential difference (PD)?

  PD = energy / charge
• What is the symbol for current?

  Capital I
• How is current defined in a circuit?

  Rate of flow of charge through a circuit
• What is the equation for current?

  I = Q / T
• How do we measure current in a circuit?

  With an ammeter connected in series
• What is resistance in a circuit?

  It resists the flow of charge or current
• What happens to energy in a bulb with resistance?

  Energy is transferred and light is emitted
• What is the relationship between PD and current in a resistor?

  They are directly proportional
• What does a straight line graph of PD versus current indicate?

  The resistor has constant resistance
• What is Ohm's Law equation?

  V = IR
• How can resistance be calculated from a graph?

  Using Ohm's Law: R = V / I
• What happens to resistance in a filament bulb as PD increases?

  Resistance changes and increases
• Why does resistance change in metals?

  Due to collisions with vibrating ions
• What is a diode's function in a circuit?

  Allows current to flow in one direction
• What does an LED do?

  Emits light when current flows
• How does resistance change with the length of a wire?

  • Resistance is directly proportional to length
  • Longer wires have higher resistance
• What are the rules for series circuits?

  • Total PD is shared among components
  • Current is the same through all components
  • Total resistance is the sum of all resistances
• What are the rules for parallel circuits?

  • PD is the same across all branches
  • Current is shared between branches
  • Adding resistors lowers total resistance
• What happens to the total PD in a series circuit?

  It is shared among the components
• What is the current like in a series circuit?

  It is the same for all components
• How is total resistance calculated in a series circuit?

  By summing all individual resistances
• What is the PD across each resistor in a series circuit with equal resistors?

  It is shared equally among them