Electricity

• What is electricity defined as?

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

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

  • A cell (or battery)
  • Wires (represented by straight lines)
  • 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 is a coulomb?

  A specific number of electrons or charge
• What does potential difference (PD) indicate?

  Energy transferred per coulomb of electrons
• If a battery has a voltage of 1 volt, how much energy is given per coulomb?

  1 joule of energy
• How is potential difference measured?

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

  6 volts
• What happens to the voltage when a voltmeter is placed across a bulb?

  It should still read 6 volts
• What does the equation for potential difference (PD) state?

  PD = energy / charge
• What is the formula for potential difference in simple form?

  V = E / Q
• What does current measure?

  The rate of flow of charges
• What is the formula for current?

  I = Q / T
• How is current measured?

  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 potential difference and current in a resistor?

  They are directly proportional
• What does a graph of PD versus current for a resistor look like?

  A straight line through the origin
• What does a steeper gradient on a PD versus current graph indicate?

  Lower resistance of the resistor
• What is Ohm's Law equation?

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

  Using R = V / I from a point
• What happens to the resistance of a bulb as PD increases?

  Resistance changes and is non-ohmic
• Why does resistance change in metals?

  Due to collisions with vibrating ions
• What is the behavior of a diode in a circuit?

  It allows current to flow in one direction
• What is an LED?

  A light-emitting diode
• What is the relationship between resistance and length of wire?

  • Resistance is directly proportional to length
  • Measured using Ohm's law
  • Straight line through the origin in a graph
• What are the rules for series circuits?

  • Total PD is shared among components
  • Current is the same for all components
  • Total resistance is the sum of all resistances
• What happens to voltage in a series circuit with equal resistors?

  It is shared equally among them
• How do you find the current in a series circuit?

  Using Ohm's law with known voltage and resistance
• What are the rules for parallel circuits?

  • PD is the same for every branch
  • Current is shared between branches
  • Adding resistors lowers total resistance
• What is the PD across resistors in parallel?

  It is the same for all resistors
• What happens to total resistance when more resistors are added in parallel?

  Total resistance decreases