Electrostatics Grade 11
Forces that charges exert on each other

• State Coulombs Law, which can be represented mathematically as:
  
  
• Solve problems using Coulomb's Law to calculate the force exerted on a charge by one or more charges in one dimension.

Electric field around single charges and groups of charges.

• Describe an electric field as a region of space in which an electric charge experiences a force.
  The direction of the electric field at a point is the direction that a positive test charge would move if placed at that point.
• Draw electric field lines for various configurations of charges
• Define the magnitude of the electric field at a point as the force per unit charge
  
  E and F are vectors.
• Deduce that the force acting on a charge in an electric field is F = QE
• Calculate the electric field at a point due to a number of point charges, using the equation:
  
  to determine the contribution to the field due to each charge.

Electric potential energy and potential

• Define the electrical potential energy of a charge as the energy it has because of its position relative to other charges that it interacts with
• Use the equation:
  
  to calculate the potential energy of a charge due to other charges.
• Define the electric potential at a point as the electrical potential energy per unit charge, i.e.
  the potential energy a positive test charge would have if it were placed at that point
• Define electric potential difference as the difference in electrical energy per unit charge between two points:
  
  The unit is volt(V), which is the same as joule per coulomb. Thus electrical potential difference is also called voltage.
• Explain lightning in terms of electric potential and potential difference and describe measures that can be taken to reduce the risk of being struck by lightning.

Capacitance, physics of the parallel plate, relation between charge, potential difference and capacitance

• Describe a parallel plate capacitor as a device that consists of two oppositely charged conducting plates separated by a small distance, which stores charge
• Define capacitance as the charge stored per volt, measured in farad (F), mathematically
  
• Solve problems involving the charge stored by, and across, capacitors
• Use the equation:
  
  to determine the capacitance of a capacitor of given dimensions or design a capacitor of given capacitance
• Calculate the electric field between the plates of a parallel plate capacitor using the equation:
  
• Explain using words and pictures why inserting a dielectric between the plates of a parallel plate capacitor increases its capacitance.

Capacitor as a circuit device

• Describe what happens to a capacitor in a DC circuit over time.
• Describe how a charged capacitor can be used to provide a large potential difference for a very short time

Electric Circuits (Grade 11)
Relation between current, voltage and resistance
Ohm's Law

• Define Electric Current
  Calculate electric current using Q = It
  (grade 10 revision)
• Determine the relationship between current, voltage and resistance at a constant temperature using a simple circuit.
• State the difference between ohmic and non-ohmic conductors, and give an example of each
• Solve problems using the mathematical expression of Ohm's Law
  
• Calculate the work done or energy transferred in an electric circuit using
  
• Calculate the electric power dissipated in an electric circuit using:
  
  Use power to determine, for example, relative brightness of bulbs.

Resistance, equivalent resistance, internal resistance

• Calculate the equivalent resistance of series and parallel arrangements of resistors.
• Solve problems involving current, voltage and resistance for circuits containing arrangements of resistors in series and in parallel
• State that a real battery has internal resistance
• Explain why there is a difference between the emf and the terminal voltage of a battery if the internal resistance in the circuit is comparable in size to the battery's internal resistance.
• Solve circuit problems in which the internal resistance of the battery must be considered.

Series, parallel, resistors

• Solve circuit problems involving resistors in series with a maximum of three resistors in parallel

Electrodynamics
Electrical machines
(generators, motors)

• State that the
  · generators convert mechanical energy to electrical energy and
  · motors convert electrical energy to mechanical energy.
• Use Faraday's Law to explain why a current is induced in a coil that is rotated in a magnetic field.
• Use words and pictures to explain the basic principle of an AC generator (alternator) in which a coil is mechanically rotated in a magnetic field
• Use words and pictures to explain how a DC generator works and how it differs from an AC generator
• Explain why a current-carrying coil placed in a magnetic field (but not parallel to the field), will turn by referring to the force exerted on moving charges by a magnetic field and the torque on the coil
• Use words and pictures to explain the basic principles of an electric motor
• Give examples of the use of AC and DC generators
• Give examples of the use of motors

Alternating current

• Explain the advantages of using alternating current
• Write expressions for the current and voltage in an AC circuit.
• Define the rms (rot mean square) values for current and voltage as:

  

  

  respectively, and explain why these values are useful
• Calculate the average power in an AC circuit using:
  
• Draw a graph of voltage vs time and current vs time for an AC circuit

Electromagnetic Radiation
Dual (particle/wave) nature of EM radiation

• Explain that aspects of the behaviour of EM radiation can best be explained using w wave model and some aspects can best be explained using a particle model

Nature of an EM-wave as mutual induction of oscillating magnetic/electric fields

• Describe the source of electromagnetic waves as an accelerating charge
• Use words and diagrams to explain how an EM wave propagates when an electric field oscillating in one plane produces a magnetic field oscillating in a plane at right angles to it, which produces an oscillating electric field, and so on.
• State that these mutually regenerating fields travel through space at a constant speed of
  3 x 10⁸m.s^-1 represented by c.

EM spectrum

• Given a list of different types of EM radiation, arrange them in order of frequency or wavelength
• Given the wavelength of EM waves, calculate the frequency and vice versa using the equation:
  
• Give an example of the use of each type of EM radiation, i.e.
  · gamma rays
  · X-rays
  · ultraviolet rays
  · visible light
  · infrared
  · microwave
  · radio and TV
  

· Nature of EM as particle
· Energy of a photon related to frequency and wavelength

• Calculate the energy of a photon using:
  

Penetrating ability

• Indicate the penetrating ability of the different kinds of EM radiation and relate it to energy of the radiation
• Describe the dangers of gamma rays, X-rays and the damaging effect of ultra-violet on skin.