Creating Models | OCR A-Level Physics B (Advancing Physics) (H557)

Creating Models

245 questions
17 subtopics
The physics content, examined on all three papers
Component 01, Component 02 and Component 03

Creating Models is examined in all three written papers — the specification states that Components 01, 02 and 03 each assess content from across all the teaching modules, so nothing is confined to one paper.

It covers capacitance and charge storage, energy stored on a capacitor, capacitor discharge and the exponential model, the time constant of an RC circuit, charging a capacitor, investigating capacitor charge and discharge, radioactive decay as a random process, activity, decay constant and half-life, Determining the half-life of an isotope, iterative numerical models of exponential change, exponential curves on linear and logarithmic scales, simple harmonic motion: the defining relationship, solutions and graphs of simple harmonic motion, modelling oscillations step by step, energy in simple harmonic motion, period of a mass–spring system and a simple pendulum and free and forced vibrations, damping and resonance.

Sample questions from Creating Models

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

Capacitance and charge storage

A capacitor holds 4.4 × 10⁻³ C when the potential difference across it is 20 V. What is its capacitance?

Show the answer
C = Q/V = 4.4 × 10⁻³ / 20 = 2.2 × 10⁻⁴ F, which is 220 μF.
Capacitor discharge and the exponential model

How can you test from a table of discharge readings whether the decay is exponential?

Show the answer
Take readings at equal time intervals and check that the ratio of each reading to the one before is constant.
Charging a capacitor

What is the expression for the current during the charging of a capacitor?

Show the answer
The current is I = I₀exp(−t/RC), with I₀ = V₀/R at the instant charging begins.
Radioactive decay as a random process

Define the decay constant.

Show the answer
It is the probability that a given nucleus will decay per unit time, and it has the unit s⁻¹.
Determining the half-life of an isotope

How is the half-life read from a graph of corrected count rate against time?

Show the answer
Read several times at which the corrected rate has halved and average the intervals between them.
Exponential curves on linear and logarithmic scales

What does the gradient of a graph of ln N against t tell you for a decaying sample?

Show the answer
The gradient is −λ, so its magnitude is the decay constant.
Solutions and graphs of simple harmonic motion

What is the phase relationship between displacement and velocity in simple harmonic motion?

Show the answer
The velocity leads the displacement by a quarter of a cycle, that is by π/2 rad.
Energy in simple harmonic motion

A spring of stiffness 20 N m⁻¹ is stretched by 0.10 m. How much energy is stored?

Show the answer
E = ½kx² = 0.5 × 20 × 0.010 = 0.10 J.

The 17 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Capacitance and charge storage	Recall questions on the defining equation and its unit, why practical values are small, charge–voltage calculations and graphs, current as charge arriving, and why the net charge is zero.	14
Energy stored on a capacitor	Recall questions on why the stored energy is not simply charge times voltage, the equivalent expressions, area under a charge–voltage graph, delivering large power briefly, and where a battery's energy goes.	14
Capacitor discharge and the exponential model	Recall questions on why capacitor discharge is exponential, dQ/dt = −Q/(RC) and its minus sign, the constant-ratio property and testing for it, Q = Q₀exp(−t/RC), potential difference and current I = I₀exp(−t/RC) during discharge, the shape of the discharge curve, successive halvings, the effect of resistance, and the initial current.	14
The time constant of an RC circuit	Recall questions on the time constant τ = RC and its unit, the 37% left after one time constant, calculating τ, the half-life t½ = τ ln 2, treating a capacitor as discharged after five time constants, finding τ from a graph or the initial tangent, the potential difference after a given time, changing R and C, and why larger capacitance slows discharge.	14
Charging a capacitor	Recall questions on Q = Q₀(1 − exp(−t/RC)) and V = V₀(1 − exp(−t/RC)), the 63% stored after one time constant, why the charging current falls and I = I₀exp(−t/RC), current–time graphs for charging and discharging, time constant and potential difference calculations, the resistor and capacitor potential differences, series resistance, and stored energy.	14
Investigating capacitor charge and discharge	Recall questions on the circuit used, what is recorded against time, choosing components so a run can be hand-timed, the time constant from a logarithmic plot, and confirming exponential decay.	14
Radioactive decay as a random process	Recall questions on the random and spontaneous nature of radioactive decay, why the decay rate is proportional to the nuclei remaining, dN/dt = −λN and the decay constant, fluctuating count rates, demonstrating randomness, why the exponential model works, subtracting background, comparing capacitor discharge with decay, heating a source, and samples of different size.	14
Activity, decay constant and half-life	Recall questions on activity and A = λN, half-life and T½ = ln 2 / λ, N = N₀exp(−λt), calculating half-lives, decay constants and activities from data, activity after several half-lives, ln A against time graphs and their gradient, and why long-lived sources stay hazardous.	15
Determining the half-life of an isotope	Recall questions on the protactinium generator method, correcting for background, reading a half-life from a decay curve or a logarithmic plot, keeping the geometry fixed, counting statistics, and handling precautions.	14
Iterative numerical models of exponential change	Recall questions on step-by-step solutions of dQ/dt = −Q/(RC) and radioactive decay, calculating single steps, why such models predict too fast a fall, improving accuracy with smaller steps and the drawback of doing so, choosing a step size, checking against N = N₀exp(−λt) and in a spreadsheet, the graphical tangent method, and negative outputs.	15
Exponential curves on linear and logarithmic scales	Recall questions on exponential decay on linear and logarithmic axes, why logarithms give a straight line, the intercept of ln V and gradient of ln N against time, spotting background counts, linearising capacitor charging, the constant-ratio property, why decay never reaches zero, gradient as current, finding the time constant, successive halvings, and logarithmic scales.	14
Simple harmonic motion: the defining relationship	Recall questions on defining simple harmonic motion, a = −ω²x and its minus sign, the restoring force condition, the mass–spring equation of motion and ω = √(k/m), ω = 2πf, amplitude and period, calculating angular frequency, maximum acceleration and maximum speed, zero acceleration at equilibrium, and why the period is independent of amplitude.	15
Solutions and graphs of simple harmonic motion	Recall questions on the sine and cosine solutions of simple harmonic motion and when each applies, writing them with frequency, the displacement–time graph, the phase of velocity and acceleration against displacement, gradients linking the graphs, greatest speed at equilibrium, amplitude, angular frequency and maximum speed from x = 0.020 sin(30t), and spotting traces that are not simple harmonic.	15
Modelling oscillations step by step	Recall questions on setting up the calculation for a mass on a spring, the starting conditions needed, recalculating acceleration each step, errors from too large a step, energy checks, and damping.	14
Energy in simple harmonic motion	Recall questions on energy stored ½kx² and Hooke's law F = kx, total energy ½mv² + ½kx², how kinetic and potential energy interchange, where kinetic energy is zero or greatest, calculating stored and total energy, maximum speed and kinetic energy at a displacement, energy in proportion to amplitude squared, and energy–displacement and energy–time graphs.	15
Period of a mass–spring system and a simple pendulum	Recall questions on the two period equations and frequency, calculations for given masses, stiffnesses and lengths, why the bob's mass does not matter, timing from equilibrium, and squared-period graphs.	15
Free and forced vibrations, damping and resonance	Recall questions on free and forced vibrations, natural frequency, damping, lightly damped, critically damped and overdamped motion, resonance and resonance curves, how damping changes the peak, the phase at resonance, observing resonance with a mass on a spring and Barton's pendulums, useful and harmful resonance, and damped car suspension.	15

Creating Models is 245 of the 2,455 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.