P3.2 (simple circuits)

• what charge do electrons and protons have?

  electrons; negative

  protons; positive
• what overall charge do atoms have?

  they are neutral due to the equal number of protons and electrons
• what happens when you rub 2 insulators together?

  they transfer electrons from one insulator to the other
• what is special about positive charges?

  they do not move
• what happens after the insulators are rubbed together?

  one ends up with extra electrons and the other ends up with not enough electrons to cancel out the positive charge
• what do we call the the charge on each object once they have been rubbed together?

  static electricity
• what happens inside an electric field?

  if another charged object is placed in the field then it will either be attracted or repelled from the other object, even if they are not touching
• what can we tell about the distance between field lines?

  the closer together the lines are, the stronger the field is at that point, and the direction of the lines are from north to south
• How do you describe current?

  The rate of flow of charged particles (charge)
• What moves in metal wires?

  Electrons
• What is the current in a single closed loop?

  The same everywhere
• What is conventional current?

  The direction of electric current going from the positive terminal to the negative terminal of the battery (opposite to electron flow)
• What is the equation for charge flow?

  Charge flow (C) = current (A) x time (s)
• What are small currents measured in?

  Milliamps
• How do you get from milliamps to amps?

  Divide by 1000
• What do you need to make current flow in a circuit?

  Potential difference
• Which terminal of a cell is at a higher potential difference?

  The positive terminal
• How do you tell which terminal is which using symbols?

  The longer line is positive and the shorter line is negative
• What happens when you apply a potential difference to a wire?

  An electric field is set up in the wire and charged electrons move straight away
• How do you measure potential difference and current?

  Potential difference: voltmeter

  Current: ammeter
• What do you measure when you connect a voltmeter across a component?

  The work done or energy transferred by the charges in that component
• What is the equation for energy transferred?

  Energy transferred (J) = potential difference (V) x charge (C)
• How can each loop work in a parallel circuit?

  They can work independently
• What does current do in a parallel circuit?

  It splits as it goes across the different loops and adds up to the total current near the battery
• What does the current in a circuit depend on?

  The potential difference of the cell or battery and the resistance of the components in the circuit
• What variable is current?

  Dependent variable as you can't choose how much current you have
• What is the equation for current with ohms law?

  Current (A) = potential difference (V) / resistance
• What is the symbol equation for ohms law?

  V= I x R
• What does the inside of a metal look like?

  Positively charged ions arranged in a regular pattern
• How is resistance produced in a metal?

  The delocalised electrons produced in bonding are free to move so often collide with the rest of the ions in the lattice
• What is a variable resistor?

  A circuit component that you can use to change the amount of resisting material and alter the resistance
• What is a graph of current against potential difference called?

  A characteristic graph
• What does the wire being a linear circuit element mean?

  It's resistance does not change as you change the potential difference
• What do you use when you need a resistance to be constant?

  A resistance wire or a resistor
• State ohms law in a sentence?

  Current is proportional to potential difference if the temperature does not change
• What happens to the resistance of a non linear circuit element?

  The resistance is not constant
• Why are thinner (and hotter) wires used in lamps?

  The electrons in the wire collide with the ions and there are more collisions so the wire gets hotter faster and create light
• When do you use a diode?

  If you want current to only flow in one direction
• Where should the long leg of an LED (diode) always connect?

  The positive terminal of a battery
• What happens if you reverse the potential difference with a diode involved?

  There is no current