Electromagnetism

This lesson comprises eight (8) master classes focusing on:

• Electric filed and forces
• Magnetic field and forces
• The motor effect
• Faraday and Lenz's laws
• Generators
• Transformers and transmission lines

Content:

PH12-13

What happens to stationary and moving charged particles when they interact with an electric or magnetic field?

• Investigate and quantitatively derive and analyse the interaction between charged particles and uniform electric fields, including:
  • electric field between parallel charged plates \( E=\frac{V}{d} \)
  • acceleration of charged particles by the electric field \( \vec{F}_{net}=m \vec{a} \), \( \vec{F}=q \vec{E} \)
  • work done on the charge \( W=qV \), \(W=qEd \), \( K=\frac{1}{2}mv^2 \)
• Model qualitatively and quantitatively the trajectories of charged particles in electric fields and compare them with the trajectories of projectiles in a gravitational field
• Analyse the interaction between charged particles and uniform magnetic fields, including:
  • acceleration, perpendicular to the field, of charged particles
  • the force on the charge \( F=qv_{\perp}B=qvB \sin \theta \)
• Compare the interaction of charged particles moving in magnetic fields to:
  • the interaction of charged particles with electric fields
  • other examples of uniform circular motion

Under what circumstances is a force produced on a current-carrying conductor in a magnetic field?

• Investigate qualitatively and quantitatively the interaction between a current-carrying conductor and a uniform magnetic field \( F=lI_{\perp}B=lIB \sin \theta \) to establish:
  • conditions under which the maximum force is produced
  • the relationship between the directions of the force, magnetic field strength and current
  • conditions under which no force is produced on the conductor
• Conduct a quantitative investigation to demonstrate the interaction between two parallel current-carrying wires
• Analyse the interaction between two parallel current-carrying wires \( \frac{F}{l}=\frac{\mu_0}{2 \pi} \frac{ I_1I_2}{r} \) and determine the relationship between the International System of Units (SI) definition of an ampere and Newton’s Third Law of Motion

How are electric and magnetic fields related?

• Describe how magnetic flux can change, with reference to the relationship \( \Phi=B_{\parallel}A=BA \cos \theta \)
• Analyse qualitatively and quantitatively, with reference to energy transfers and transformations, examples of Faraday’s Law and Lenz’s Law \( \varepsilon=−N \frac{\bigtriangleup \Phi}{\bigtriangleup t} \), including but not limited to:
  • the generation of an electromotive force (emf) and evidence for Lenz’s Law produced by the relative movement between a magnet, straight conductors, metal plates and solenoids
  • the generation of an emf produced by the relative movement or changes in current in one solenoid in the vicinity of another solenoid
• Analyse quantitatively the operation of ideal transformers through the application of:
  • \( \frac{V_p}{V_s}=\frac{N_p}{N_s} \)
  • \(V_pI_p=V_sI_s \)
• Evaluate qualitatively the limitations of the ideal transformer model and the strategies used to improve transformer efficiency, including but not limited to:
  • incomplete flux linkage
  • resistive heat production and eddy currents
• Analyse applications of step-up and step-down transformers, including but not limited to:
  • the distribution of energy using high-voltage transmission lines

How has knowledge about the Motor Effect been applied to technological advances?

• Investigate the operation of a simple DC motor to analyse:
  • the functions of its components
  • production of a torque \( \tau=nIA_{\perp}B=nIAB \sin \theta \)
  • effects of back emf
• Analyse the operation of simple DC and AC generators and AC induction motors
• Relate Lenz’s Law to the law of conservation of energy and apply the law of conservation of energy to:
  • DC motors and
  • magnetic braking

PH12-1

• Develop and evaluate inquiry questions and hypotheses to identify a concept that can be investigated scientifically, involving primary and secondary data
• Modify questions and hypotheses to reflect new evidence

PH12-2

• Assess risks, consider ethical issues and select appropriate materials and technologies when designing and planning an investigation
• Justify and evaluate the use of variables and experimental controls to ensure that a valid procedure is developed that allows for the reliable collection of data
• Evaluate and modify an investigation in response to new evidence

PH12-3

• Employ and evaluate safe work practices and manage risks
• Use appropriate technologies to ensure and evaluate accuracy
• Select and extract information from a wide range of reliable secondary sources and acknowledge them using an accepted referencing style

PH12-4

• Select qualitative and quantitative data and information and represent them using a range of formats, digital technologies and appropriate media
• Apply quantitative processes where appropriate
• Evaluate and improve the quality of data

PH12-5

• Derive trends, patterns and relationships in data and information
• Assess error, uncertainty and limitations in data
• Assess the relevance, accuracy, validity and reliability of primary and secondary data and suggest improvements to investigations