§-Module

Unit 3: How do fields explain motion and electricity?

10 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do physicists explain motion in two dimensions?

model the force vectors acting on an object on a banked track moving in uniform circular motion in a horizontal plane and identify the design speed at which friction is not required to keep the object on the track

A focused answer to the VCE Physics Unit 3 dot point on banked tracks. Covers the free-body diagram of a car on a banked curve, the derivation of the design speed at which no friction is needed ( $\\tan\\theta = v^2 / rg$ ), and the worked example for a typical motorway off-ramp.

9 min answer →

investigate and analyse theoretically and practically the uniform circular motion of an object moving in a horizontal plane and on a vertical circle, including a quantitative analysis of the forces acting at the top and bottom of the vertical circle

A focused answer to the VCE Physics Unit 3 dot point on circular motion. Covers centripetal acceleration and force, the period-speed-radius relationships, the conical pendulum on a horizontal circle, and the forces at the top and bottom of a vertical loop (roller coasters, buckets of water, balls on strings).

11 min answer →

investigate and apply theoretically and practically Newton's three laws of motion in situations where two or more coplanar forces act along a straight line and in two dimensions; apply the concepts of momentum and impulse, including the conservation of momentum in one and two dimensions, and distinguish between elastic and inelastic collisions

A focused answer to the VCE Physics Unit 3 dot point on Newton's laws, momentum and impulse. Covers force, mass and acceleration in two dimensions, impulse as the area under a force-time graph, conservation of momentum in 1D and 2D collisions, and how to tell elastic from inelastic collisions.

11 min answer →

investigate and analyse theoretically and practically the motion of projectiles near Earth's surface including a qualitative description of the effects of air resistance

A focused answer to the VCE Physics Unit 3 dot point on projectile motion. Covers resolving the launch velocity into independent horizontal and vertical components, applying constant-velocity equations horizontally and SUVAT vertically with $g = 9.8$ m/s squared, the standard worked range and maximum height example, and a qualitative treatment of air resistance.

9 min answer →

How do things move without contact?

describe electric fields using the field model, apply Coulomb's law

F = k q_1 q_2 / r^2

and the relationships

E = F/q

E = kQ/r^2

for point charges and

E = V/d

for the uniform field between parallel plates; identify the directions of field, force and acceleration of charged particles in uniform and radial fields

A focused answer to the VCE Physics Unit 3 dot point on electric fields. Covers the field model, Coulomb's law for point charges, the radial field $E = kQ/r^2$ , the uniform field between parallel plates $E = V/d$ , the force and acceleration on a charged particle in each, and the conventional directions used by VCAA.

11 min answer →

describe gravitation using a field model and apply Newton's law of universal gravitation

F = G m_1 m_2 / r^2

and the relationships

g = G M / r^2

g = F/m

, the work done by a gravitational field

W = \Delta U = mg \Delta h

in a uniform field and the change in gravitational potential energy in non-uniform fields as the area under a force-distance graph

A focused answer to the VCE Physics Unit 3 dot point on gravitational fields. Covers the field model and field lines, Newton's law of universal gravitation, the equivalence of $g$ as field strength and as acceleration, gravitational potential energy in uniform and non-uniform fields, and how to read change in $U$ as the area under a $F$ vs $r$ graph.

12 min answer →

describe magnetic fields around magnets, current-carrying wires and solenoids; apply the right-hand rule to determine the directions of fields and forces; apply

F = qvB

for a charged particle moving perpendicular to a uniform magnetic field, including circular motion of the particle

A focused answer to the VCE Physics Unit 3 dot point on magnetic fields. Covers field shapes around bar magnets, straight wires and solenoids, the right-hand grip and slap rules, the force on a moving charge ( $F = qvB$ ), and the resulting circular motion of a charged particle in a uniform field.

11 min answer →

How are fields used in electricity generation?

investigate and apply theoretically and practically electromagnetic induction using the concepts of magnetic flux

\Phi_B = B_\perp A

, induced EMF

\varepsilon = -N \Delta\Phi_B / \Delta t

(Faraday's law) and Lenz's law to determine the direction of the induced current

A focused answer to the VCE Physics Unit 3 dot point on electromagnetic induction. Covers magnetic flux $\\Phi_B = B_\\perp A$ , Faraday's law for the induced EMF, Lenz's law for the direction of the induced current, and the standard worked example of a bar magnet falling through a coil.

11 min answer →

explain the operation of AC and DC generators, distinguish between peak and RMS values of voltage and current using

V_{RMS} = V_{peak} / \sqrt{2}

and

I_{RMS} = I_{peak} / \sqrt{2}

, and apply the ideal transformer relationship

V_1 / V_2 = N_1 / N_2 = I_2 / I_1

to AC power transmission, including resistive losses

P_{loss} = I^2 R

A focused answer to the VCE Physics Unit 3 dot point on AC and DC generators, RMS values and the ideal transformer. Covers slip rings vs split-ring commutators, the sinusoidal EMF from a rotating coil, the relationship between peak and RMS quantities, and why power is transmitted at high voltage to minimise $I^2 R$ losses.

12 min answer →

investigate and analyse theoretically and practically the force on a current-carrying conductor in a magnetic field,

F = n B I L

, and apply this to the operation of a simple DC motor including the role of the split-ring commutator

A focused answer to the VCE Physics Unit 3 dot point on the force on a current-carrying conductor in a magnetic field. Covers $F = n B I L$ , the right-hand slap rule, the torque on a current loop, and the operation of a simple DC motor including the role of the split-ring commutator in keeping the rotation in one direction.

11 min answer →