Fields and Their Consequences | AQA A-Level Physics (7408)

Fields and Their Consequences

422 questions
18 subtopics
Paper 2, and available on Paper 3
Paper 2 and Paper 3

Fields and their consequences is examined on Papers 2 and 3, and is the largest topic in the second year.

It treats gravitational, electric and magnetic fields side by side, drawing out what they share, then covers capacitance and electromagnetic induction.

Sample questions from Fields and Their Consequences

Answer each one closed book first, then open the answer.

Fields

What type of interaction gives rise to gravitational force fields?

Show the answer
The interaction of mass.
Gravitational field strength

What is the SI unit of gravitational field strength?

Show the answer
Newtons per kilogram (N kg⁻¹).
Orbits of planets and satellites

How is the total energy of an orbiting satellite related to its kinetic and potential energies?

Show the answer
E_total = Eₖ + Eₚ = GMm/(2r) + (−GMm/r) = −GMm/(2r)
Electric field strength

State an alternative unit for electric field strength that is equivalent to N C⁻¹.

Show the answer
Volts per metre (V m⁻¹).
Capacitance

Why is the farad considered a very large unit in practical circuits?

Show the answer
Because most capacitors store only small amounts of charge per volt, so capacitances are typically measured in microfarads (μF), nanofarads (nF), or picofarads (pF).
Energy stored by a capacitor

Calculate the energy stored when capacitance = 0.000669 F, potential difference = 6 V.

Show the answer
Energy stored = 0.5 × 0.000669 × 6 × 6 = 0.012 J.
Magnetic flux density

In Fleming's left hand rule, what does the first finger represent?

Show the answer
The direction of the magnetic field.
Magnetic flux and flux linkage

In the formula Φ = BA, what physical quantities must you know to determine the magnetic flux?

Show the answer
The magnetic flux density (B) and the area perpendicular to the field (A).

The 18 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Fields	What a force field is, and the parallels between gravitational and electrostatic fields.	11
Newton's law	Newton's law of gravitation, the gravitational constant, and the inverse-square relationship.	18
Gravitational field strength	Defining g by force per unit mass, radial fields, and reading field lines.	19
Gravitational potential	Potential and potential difference, equipotential surfaces, and the graphs of g and V against r.	25
Orbits of planets and satellites	Orbital speed and period, T² ∝ r³, the energy of an orbiting satellite, escape velocity and synchronous orbits.	45
Coulomb's law	The force between point charges, permittivity of free space, and comparison with gravitation.	17
Electric field strength	Field strength in uniform and radial fields, E = V/d, and the path of a charge in a uniform field.	20
Electric potential	Absolute potential and potential difference, equipotentials, and the relationship between E and V.	24
Capacitance	Defining capacitance, the farad, and the relationship between charge, voltage and capacitance.	15
Parallel plate capacitor	Permittivity and relative permittivity, dielectrics, and how a polar molecule responds to a field.	25
Energy stored by a capacitor	The three energy formulae, and finding the energy from the area under a charge-voltage graph.	15
Capacitor charge and discharge	The time constant, the exponential equations, and the log-linear graphs used to find RC.	41
Magnetic flux density	The force on a current-carrying wire, Fleming's left hand rule, and the current balance experiment.	23
Moving charges in a magnetic field	F = BQv, circular motion in a field, and the cyclotron.	29
Magnetic flux and flux linkage	Magnetic flux and flux linkage, and how both vary for a rotating coil.	33
Electromagnetic induction	Faraday's law and Lenz's law, the emf induced by a moving conductor, and the alternator.	22
Alternating currents	Peak, peak-to-peak and root mean square values, and using an oscilloscope.	26
Transformers	The transformer equation, efficiency, and why the National Grid transmits at high voltage.	14

Fields and Their Consequences is 422 of the 3,682 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.