Electricity | 10th IGCSE Physics

Schedule

(20 periods)

Content

• Electrostatics
• Current
• Potential difference
• Ohm's law
• Electric Power
• Electronics
• Digital electronics
• Electrical safety

Instructional objectives

Students should be able to:

• Electrostatics:
  • Describe simple experiments to show the production and detection of electrostatic charges
  • State that charging a body involves the addition or removal of electrons
  • State that charge is measured in coulombs
  • State that the direction of an electric field at a point is the direction of the force on apositive charge at that point
  • Describe an electric field as a region in which an electric charge experiences a force
  • Describe simple field patterns, including the field around a point charge, the field around a charged conducting sphere and the field between two parallel plates (not including end effects)
  • Give an account of charging by induction
  • Distinguish between electrical conductors and insulators and give typical examples
  • Recall and use a simple electron model to distinguish between conductors and insulators
• Current
  • State that current is related to the flow of charge
  • Use and describe the use of an ammeter, both analog and digital
  • State that current in metals is due to a flow of electrons
  • Show understanding that a current is a rate of flow of charge and recall and use the equation I = Q / t
  • Distinguish between the direction of flow of electrons and conventional current
• Potential difference
  • State that the e.m.f. of an electrical source of energy is measured in volts
  • Show understanding that e.m.f. is defined in terms of energy supplied by a source in driving charge round a complete circuit
  • State that the potential difference (p.d.) across a circuit component is measured in volts
  • Use and describe the use of a voltmeter, both analogue and digital
  • Recall that 1V is equivalent to 1 J/C
• Ohm's law
  • Recall and use the equation R = V / I
  • Describe an experiment to determine resistance using a voltmeter and an ammeter
  • Relate (without calculation) the resistance of a wire to its length and to its diameter
  • Sketch and explain the current-voltage characteristic of an ohmic resistor and a filament lamp
  • Recall and use quantitatively the proportionality between resistance and length, and the inverse proportionality

between resistance and cross-sectional area of a wire

• Electric power:
  • Recall and use the equations P = IV and E = IVt

Electronics:
* Draw and interpret circuit diagrams containing sources, switches, resistors (fixed and variable), heaters, thermistors, light-dependent resistors, lamps, diodes, ammeters, voltmeters, galvanometers, magnetising coils, transformers, bells, fuses and relays
* Describe the functioning of a capacitor
* Describe the action of a variable potential divider (potentiometer)
* Describe the action of thermistors and light dependent resistors and show understanding of their
use as input transducers
* Describe the action of a relay and show understanding of its use in switching circuits
* Describe the action of a diode and show understanding of its use as a rectifier
* Recognise and show understanding of circuits operating as light-sensitive switches and temperature-operated alarms (to include the use of a relay)
* Explain and use the terms analogue and digital in terms of continuous variation and high/low states
* Describe the action of NOT, AND, OR, NAND and NOR gates
* Recall and use the symbols for logic gates
* Design and understand simple digital circuits combining several logic gates
* Use truth tables to describe the action of individual gates and simple combinations of gates

Teaching Process

• Start out with discussions on static electricity.
• Students build an electroscope
• Electronics is learnt by using the components to understand its behavior
• Some circuits are built by the students on the breadboard by the students.

Activities

• Making an electroscope
• Making a Leyden jar
• Measuring resistance and resistivity
• Find out resistance, current and voltage in series and parallel circuits using the appropriate equations
• Build simple circuits
• Build a light sensitive switch using LDR and transistors
• Build a rectifier

Suggested reading / References

• How we found out about electricity - Isaac Asimov

Assignments / Evaluation

• Builing electroscope
• Building leyden jar
• Test