VCAA Physics How are fields used in electricity generation?

This rotation speed is too slow. Using the formula $\varepsilon_{avg} = 4NBAf$, a frequency of $1 \text{ rev/s}$ would only produce an average EMF of $0.48 \text{ V}$.

This value is insufficient. Substituting $f=3$ into the average EMF equation yields approximately $1.44 \text{ V}$, which is less than the required $6 \text{ V}$.

This frequency is too high. At $50 \text{ rev/s}$, the generated average EMF would be $24 \text{ V}$, far exceeding the required $6 \text{ V}$.

While transformers are indeed used to step up the voltage, this explains how high voltages are achieved, not why they are beneficial for long-distance transmission.

While high voltages are used to transmit large amounts of power, the fundamental reason for stepping up the voltage is to minimize power loss during transmission, not just to increase capacity.

The resistance of a transmission line is determined by its physical properties (material, length, and cross-sectional area), not by the voltage applied to it.

This value is incorrect. It does not reflect the proportional relationship where EMF scales with the product of the number of turns and the cross-sectional area.

This answer is incorrect. It implies a much larger increase in EMF than what is mathematically predicted by the changes in coil geometry.

This result would be obtained if the area were doubled instead of halved ($0.75\text{ V} \times 3 \times 2 = 4.5\text{ V}$). However, the problem states the area is half the original size.

This is the ratio of the primary voltage to the secondary voltage ($240 \text{ V} / 5.0 \text{ V} = 48$), not the current drawn from the mains.

This is the inverse of the primary current ($240 / 15 = 16$), which results from incorrectly dividing the primary voltage by the secondary power.

This value does not correspond to the correct application of the ideal transformer equation. It may result from an incorrect combination of the given values.

This is incorrect. It does not match the result derived from Faraday's Law using the given values for loops, flux change, and EMF.

This is incorrect. The calculation using the formula $\Delta t = \frac{N \Delta \Phi}{\varepsilon}$ yields 0.2 s, not 2.2 s.

This is incorrect. This result likely comes from incorrectly inverting the formula to $\Delta t = \frac{\varepsilon}{N \Delta \Phi}$, which results in $5.0 \text{ s}$.

The magnetic field lines generated by a current circle around the wire, making them perpendicular, not parallel, to the electric field driving the current.

The strength of the induced magnetic field is directly proportional to the current, which is directly proportional to the electromotive force (EMF) via Ohm's Law ($I = V/R$).

Induction requires a changing magnetic flux; once the magnet is removed and the flux stops changing, the induced current and its magnetic field cease.

This would be the output if the input was 240 V AC, calculated using the transformer equation $V_s = V_p \times \frac{N_s}{N_p}$. However, transformers do not work with DC voltage.

This assumes an AC input and incorrectly inverts the turns ratio, calculating $V_s = V_p \times \frac{N_p}{N_s}$. Furthermore, transformers do not operate on DC voltage.

This value is obtained by simply multiplying all the given numbers together ($240 \times 2000 \times 80$), which does not correspond to any valid physical formula for transformers.

This describes electromagnetic induction, a specific mechanism that generates EMF, rather than the general definition of electromotive force itself.

This describes the electrostatic force (Coulomb repulsion) between like charges, whereas EMF is a potential difference measured in Volts ($V$), not a force measured in Newtons ($N$).

Despite its name, electromotive force is not a force in the physical sense (measured in Newtons); it is an electric potential. The fundamental force is the electromagnetic force.

Increasing the number of turns on the primary coil would decrease the output voltage, as the secondary voltage is proportional to the ratio of secondary to primary turns ($V_s = V_p \times \frac{N_s}{N_p}$).

Increasing the resistance connected to the secondary coil affects the current drawn by the load, but it does not change the output voltage of an ideal transformer.

Decreasing the resistance connected to the secondary coil would increase the secondary current, but the output voltage is determined solely by the input voltage and the turns ratio.

This statement defines the Law of Conservation of Charge, which states that the net charge of an isolated system cannot change.

This describes the concept of self-inductance, where a changing current induces a magnetic flux, but it does not define Lenz's Law.

This statement defines Snell's Law, which relates the angles of incidence and refraction to the refractive indices of two media.