Electricity

• Which out of a pump, battery, cell and engine is a power soruce for a electric circuit

  • Battery
  • Cell
• fill in the blanks

  A) switch open

  B) switch closed

  C) cell

  D) battery

  E) diode

  F) resistor

  G) variable resistor

  H) LED

  I) lamp

  J) fuse

  K) voltmeter

  L) ammeter

  M) thermistor

  N) LDR

  
• Current is a measure of the flow of electrons around a circuit
• Amperes, amps or 'A' are the units of?

  Current
• Potential difference is the force driving the flow of electrons around a circuit
• In 'conventional current', we say that the electrons flow from?

  Positive terminal --> negative terminal
• Resistance is everything that resists or opposes the flow of electrons in a circuit
• Voltage, volts or 'V' are all used to refer to?

  Potential difference
• Ohms (Ω) are the units of?

  Resistance
• What is the formual which relates voltage, current and resistance?

  $V=$$IR$
• The digram is a current/voltage graph for a?

  Fixed Resistor

  
• For wires and resistors, increasing the tempurature will increase the resistance. This is because all of the ions in the metal vibrate faster which makes it harder for electrons to pass along the wire.
• The diagram is a current/voltage graph for a?

  Filament lamp

  
• What do diodes do?

  Only allow current to flow one way around a circuit
• The diagram is a current/voltage graph for a?

  Diode

  
• Charge is a measure of the total current that flowed within a period of time
• The formula for charge is:

  charge = current x time

  Symbol formula:

  Q = It
• The units for charge are?

  Coulombs (C)
• A light emmiting diode will:

  • Emit light when current flows throught it
  • Only allow current to flow in one direction
• Ammeters

  • They measure current
  • They are added to a circuit in series
• Voltmeters

  • They measure potential difference
  • They are added to a circuit in parallel
• A resistor whose resistance decreases when temperature increases is a:

  Thermistor
• Which type of resistor allows us to easily adjust its resistance?

  Variable resistor
• A resistor which cannot vary the amount of resistance it provides is a?

  Fixed resistor
• In which type of resistor does the resistance vary with light intensity?

  Light dependent resistor (LDR)
• In a series circuit the potential difference of the battery is shared across all of the components
• In a series circuit the current is the same everywhere in the circuit
• In a series circuit, the total resistance is equal to the sum of the individual resistances of each component
• In a series circuit, components with greater resistance will always have a greater share of the voltage
• In a parallel circuit if one component breaks the overall circuit will still work. This is because current can flow throught the other loops.
• All the components in a parallel circuit have the same potential difference
• The total current in a parallel circuit is shared between all of the parallel loops
• Adding a resistor in a parallel circuit decreases the current through the circuit.
• Formulas for energy:

  • Energy (E) = Power (P) x Time (t)
  • Energy (E) = Voltage (V) x Current (I) x Time (t)
  • Energy (E) = Charge (Q) x Voltage (V)