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 $6 \text{ V}$.

Incorrect. This value is obtained by dividing the RMS current by $\sqrt{2}$, which does not give the peak-to-peak current.

Incorrect. This is the peak current ($I_{peak} = I_{rms} \times \sqrt{2}$), but the question asks for the peak-to-peak current, which is twice this value.

Incorrect. This value does not correspond to the correct conversion factor of $2\sqrt{2}$ needed to find the peak-to-peak current from the RMS current.

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.

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 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 is the primary (input) current, calculated as $I_p = P_{in} / V_p = 40 \text{ W} / 240 \text{ V} \approx 0.17 \text{ A}$, rather than the secondary (output) current.

This value likely comes from confusing the turns ratio ($6:1$) with the actual output current, or incorrectly multiplying the $1.0 \text{ A}$ output current by $6$.

This is a miscalculation. The correct output current must be found by dividing the conserved power ($40 \text{ W}$) by the stepped-down secondary voltage ($40 \text{ V}$).

Incorrect. This value is approximately $240 / \sqrt{2}$, which incorrectly divides the RMS voltage by $\sqrt{2}$ instead of multiplying it to find the peak voltage.

Incorrect. This is the peak voltage ($V_{peak} = \sqrt{2} \times 240 \approx 340$ V), but the question asks for the peak-to-peak voltage, which is double this value.

Incorrect. This value is simply double the RMS voltage ($2 \times 240 = 480$ V), which ignores the $\sqrt{2}$ factor required to convert RMS to peak voltage.

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.

Transformers are actually used to step down (decrease) the voltage in cities to safe levels for consumer use, not increase it.

High voltages actually result in smaller currents for a given power output. It is the reduction in current, not an increase, that makes transmission efficient.

The resistance of transmission lines is determined by their physical properties (material, length, and cross-sectional area), not by the voltage transmitted through them.

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.