# Year 12 – Electromagnetism

###### Charged Particles, Conductors and Electric and Magnetic Fields

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

Students:

• investigate and quantitatively derive and analyse the interaction between charged particles and uniform electric fields, including: (ACSPF083)
• electric field between parallel charged plates $\big( \lvert\vec{E}\rvert = - \frac{V}{\vec{d}}\big)$
• acceleration of charged particles by the electric field $(\vec{F} = m\vec{a}, \vec{F} = q\vec{E})$
• 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: (ACSPH083)
• acceleration, perpendicular to the field, of charged particle
• the force on the charge $(\vec{F} = q\vec{v}\vec{B}\sin{\theta})$
• 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 (ACSPH108)

Resource – Charged Particles in Electric Fields 1 – 2 pages

The Motor Effect

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

Students:

• investigate qualitatively and quantitatively the interaction between a current-carrying conductor and a uniform magnetic field $(\vec{F} = \vec{B}I\vec{l}\sin{\theta})$
• to establish: (ACSPH080, ACSPH081)
• 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 $\big(\frac{\vec{F}}{l} = \frac{\mu_0}{2\pi}\times\frac{I_1 I_2}{\vec{r}}\big)$ and determine the relationship between the International System of Units (SI) definition of an ampere and Newton’s Third Law of Motion (ACSPH081, ACSPH106)

Resource – Charged Particles in Electric Fields 2 – 2 pages

Electromagnetic Induction

Inquiry question: How are electric and magnetic fields related?

Students:

• describe how magnetic flux can change, with reference to the relationship $\phi = BA$
• (ACSPH083, ACSPH107, ACSPH109)
• analyse qualitatively and quantitatively, with reference to energy transfers and transformations, examples of Faraday’s Law and Lenz’s Law $\big(\epsilon = -N\frac{\Delta\phi}{\Delta t} \big)$, including but not limited to: (ACSPH081, ACSPH110)
• 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 the ideal transformers through the application of: (ACSPH110)
• $\frac{V_p}{V_s} = \frac{N_p}{N_s}$
• $V_p I_p = V_s I_s$
• evaluate qualitatively the limitations of the ideal transformer model and the strategies used to improve transformer efficiency, including but not limited to:
• 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

Resource – Electromagnetic Induction – 2 pages

Applications of the Motor Effect

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

Students:

• investigate the operation of a simple DC motor to analyse:
• the functions of its components
• production of a torque $(\vec{\tau} = nBIA\cos{\theta})$
• effects of back emf (ACSPH108)
• analyse the operation of simple DC and AC generators and AC induction motors (ACSPH110)
• 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