physics P3 EOT exam

• what is the structure of atoms?

  nucleus, shells, protons, neutrons and electrons
• what do like and unlike charge do?

  like charges repel unlike charges attract
• define electric current and how do you calculate it

  the rate of flow of charge Q=It
• what is potential difference and how do you calculate it?

  Potential difference is the difference in electric potential between two points in an electric field. V=E/Q
• why does a potential difference cause a current to flow in a wire?

  a potential difference is applied across the wire making one end positive and the other end negative.Electrons are attracted to the positive end and repelled from the negative end and so feel a resultant force causing them to flow
• what is resistance and how do you calculate it?

  how much current is impeeded V=IR
• what is the difference between series and parallel circuit?

  series-one loop and only one route for the electrons to go through

  parallel-has more than one branch and more routes for the electrons to go through
• how are P.D. and current shared in series and parallel

  series-current is same everywhere

  parallel-current is shared between loops

  series-P.D. is shared between components

  parallel-P.D. is the same
• what are the IV graphs for: ohmic resistor, diode and bulb

  these are the IV graphs:

  
• what is the purpose of diodes, thermistors and LDR'S?

  Diodes: Allow current to flow in one direction. Thermistors: Change resistance with temperature. LDRs (Light Dependent Resistors): Change resistance with light intensity.
• what are AC and DC and which one is the mains?


  AC and DC are types of electrical current.

  AC-alternating current and DC-direct current.

  AC is the type of current used in mains electricity.
• what wires are in a plug and what colour and jobs do each have?

  Live (brown) - carries current to the appliance

  Neutral (blue) - completes the circuit

  Earth (green and yellow) - provides a path for fault current to prevent electric shock
• why do we have step up transformers before pylons on the national grid?

  to increase potential difference and to decrease current so it wont create a spark