VCAA Physics How do things move without contact?

This describes the domain for calculating magnetic flux, which is the integral of the magnetic field over an area, rather than defining the field itself.

This is a generic definition that could apply to gravitational or electric fields; it fails to specify that the force is magnetic or that it acts on magnets and moving charges.

This is the definition of an electric field, which exerts forces on stationary or moving electric charges, whereas magnetic fields specifically affect moving charges or magnetic materials.

Kinetic energy is calculated as $KE = \frac{1}{2}mv^2$. Since their speeds are different, their kinetic energies cannot be the same.

According to Kepler's Third Law ($T^2 \propto r^3$), satellites at different radii will have different orbital periods.

The gravitational force depends on the orbital radius ($F = \frac{GMm}{r^2}$). Since their radii are different, the forces exerted on them will also be different.

A circular orbit requires a negative total energy and a launch parallel to the surface at a specific orbital velocity, which is less than the escape velocity.

An elliptical orbit requires the total energy of the system to be negative, meaning the launch velocity must be strictly less than the escape velocity.

While the trajectory is indeed a parabola, an object launched at or above escape velocity will overcome the planet's gravity and never return to land.

This describes Kepler's First Law, also known as the Law of Ellipses, which states that planets move in elliptical orbits with the Sun at one focus.

Kepler's laws are not derived from combining Newton's first law with uniform circular motion; rather, the third law relates orbital period to distance.

This describes Kepler's Second Law, or the Law of Equal Areas, which states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

Decreasing wire thickness increases electrical resistance, which would reduce the current $I$ (for a fixed voltage) and consequently decrease the magnetic field strength.

The magnetic field strength $B = \mu_0 \frac{N}{L} I$ is inversely proportional to the length $L$; increasing the length while keeping the number of turns constant decreases the turn density, weakening the field.

Alternating current produces a magnetic field that fluctuates in magnitude and direction, and inductive reactance often reduces the current compared to DC, which would not increase the field strength.

This is the value for the electric potential ($V = \frac{kQ}{r}$), not the electric field strength ($E = \frac{kQ}{r^2}$).

This value represents the electric potential calculated incorrectly by using the mass number (4) instead of the atomic number (2) for the charge.

This result comes from incorrectly using the mass number (4) instead of the atomic number (2) to calculate the total charge ($Q = 4e$).

This value is too small. The calculated magnetic field strength is approximately $0.015 \text{ T}$, which is two orders of magnitude larger than $10^{-4} \text{ T}$.

This value is significantly larger than the actual magnetic field. The calculation yields $B \approx 0.015 \text{ T}$, whereas $10^2 \text{ T}$ represents an extremely strong magnetic field not supported by the data.

This value is far too large. The calculated field strength is approximately $1.5 \times 10^{-2} \text{ T}$, which is six orders of magnitude smaller than $10^4 \text{ T}$.

This describes electric field strength ($E$), which is the force exerted per unit charge at a specific location, not the energy.

This describes electric potential difference (voltage), which is the difference in electric potential energy per unit charge between two points.

This is the specific definition of an electron-volt (eV), a unit of energy, rather than the general definition of electrical potential energy.

The gravitational force between two objects with mass is never zero, as gravity acts over infinite distances.

This value is far too small and likely results from a significant calculation error, such as ignoring the exponents in the scientific notation.

This value is incorrect and may result from failing to square the orbital radius $r$ in the denominator of the gravitational force formula.