Electromagnetic Technologies and Society

A superconductor has no resistance, so a very large current can flow without producing heat (no I²R loss). That makes a very strong, steady field possible at a reasonable running cost.

Benefit (any): detailed soft-tissue images without ionizing radiation. Risk/cost (any): steel objects can become projectiles in the strong field; implants must be screened; machines are expensive, which affects wait times.

The loop carries an alternating current, which makes a changing magnetic field. A car's steel body above the loop changes the loop's magnetic properties, and the control box detects that change (electromagnetic induction).

Any two: drivers/vehicle owners, pedestrians and cyclists, municipalities, police, taxpayers.

Sample: What exactly is recorded? How long are images stored? Who can access them, and can they be used for other purposes? Is the system secure?

Sample: a known, qualified author or organization; evidence and data with references; recent; and no conflict of interest (or the interest is clearly stated). Government, university and peer-reviewed sources are usually more reliable than ads or anonymous posts.

Magnetic resonance imaging.

Magnetic levitation.

TRIUMF (Vancouver) or the Canadian Light Source (Saskatoon).

Faraday's law of electromagnetic induction (a changing magnetic field induces a signal).

Any one: the cost of a dedicated guideway, land purchase, power systems, trains, maintenance.

They float above the guideway, so there is no rolling friction and no wheel wear; the main resistance is air. Linear motors in the guideway can push them without relying on wheel grip.

Social (any two): patient wait times, access for rural patients, staff workload and safety, which patients get priority. Economic (any two): purchase and installation cost, staff wages, running costs (electricity, cooling, maintenance), savings from earlier diagnosis.

The camera photographs the vehicle and its plate, not reliably the driver, so the ticket is issued to the owner. Criticism: an owner may be fined for someone else's driving, and no demerit points are given, so a dangerous driver might not be held fully responsible.

With caution: the company has a financial interest. Check its claims (for example, efficiency or charging time) against independent sources such as consumer testing groups, university studies or government reports.

Charged particles (ions) moving through a magnetic field feel a force (motor principle) that bends their paths. Ions of different masses bend by different amounts, so they can be separated and identified.

Model answer: Red-light cameras use induction loops, which detect vehicles by a change in a magnetic field, to photograph vehicles entering an intersection on a red light. Supporters argue they reduce red-light running and dangerous right-angle collisions, and they enforce the law all day without tying up police. Critics raise privacy concerns about stored images and argue that cameras are sometimes placed where they raise the most revenue rather than where they prevent the most harm. Tickets go to vehicle owners without demerit points, which some see as unfair. A reasonable policy is to add cameras where collision data show a problem, publish before-and-after results, and set strict limits on how long images are stored and who may see them. Look for: physics described correctly, both sides, evidence-based reasoning and a clear, qualified position.

A rapidly changing magnetic field induces potential differences in conductors (Faraday's law); long conductors such as transmission lines can pick up large induced currents, which can overheat and damage transformers. Protections (any one): monitoring space weather and reducing loads during storms, devices that block or divert the extra currents, shielding sensitive electronics, keeping spare transformers.

Induction: heats the pot directly by induced currents, so more of the energy goes into the food; no combustion in the home (better indoor air); Ontario's electricity is mostly low-carbon (nuclear and hydro), so emissions are low. Costs: the cooktop may cost more, and pots must be magnetic (iron or steel). Gas: cheaper appliance in some cases and familiar, but burns natural gas, a fossil fuel, releasing CO₂ and indoor combustion products. The best choice depends on purchase cost, energy prices and how much weight is given to emissions and indoor air quality.