GCSE Physics Paper 1 (OCR) Revision

Comprehensive practice flashcards covering all core topics from OCR GCSE Physics Paper 1, including units, atomic structure, density, thermal physics, forces and motion, electricity, and electromagnetism.

How is a measurement of $5\,\mu\text{m}$ converted to meters in standard form?

Micrometers are divided by $1,000,000$ ($10^6$), which yields $5 \times 10^{-6}\,\text{m}$.

By what factor do standard metric unit prefixes scale up or down, excluding centi- and deci-?

They scale up or down in multiples of thousands ($\times 1,000$ or $\div 1,000$).

What discovery did JJ Thompson make regarding the atom, and what model did he propose?

He discovered that atoms are composed of positive and negative charges and proposed the plum pudding model, where electrons are dotted around inside a positive charge.

What did Ernest Rutherford discover about atomic structure?

He discovered that the positive part of the atom is incredibly small and located at the center, which is called the nucleus, with electrons positioned far away from it.

What contribution did Neils Boore make to the model of the atom?

He discovered that electrons exist in shells or orbitals.

What did James Chadwick discover inside the atomic nucleus?

He discovered neutral particles within the nucleus, which he called neutrons.

In an element's symbol, what information do the atomic number and mass number provide?

The bottom atomic number is the number of protons (which determines the element), and the top mass number is the total number of protons and neutrons in the nucleus.

What is an isotope?

Atoms of the same element that have the same number of protons but different numbers of neutrons.

What is the formula and standard SI unit for density?

$\text{density} = \frac{\text{mass}}{\text{volume}}$ (symbol $\rho$), measured in $\text{kg/m}^3$.

What are the typical measurement resolutions of a standard ruler, a vernier caliper, and a micrometer?

A standard ruler has a resolution of $1\,\text{mm}$, a vernier caliper has a resolution of $0.1\,\text{mm}$, and a micrometer has a resolution of $0.01\,\text{mm}$.

How is the volume of an irregular solid measured using a Eureka (displacement) can?

The object is tied to thin string and lowered under the water line of a brimmed can; the displaced water exits the spout and is collected in a measuring cylinder to read the volume.

How do the arrangement and motion of particles differ across solids, liquids, and gases?

In solids, particles vibrate about fixed positions; in liquids, particles touch but are free to move past each other; in gases, particles are far apart and move randomly.

What is the definition of internal energy?

Internal energy is the sum of the kinetic energy and potential energy of all particles in the substance.

Why does the temperature of a substance remain constant during a change of state?

The supplied energy increases the potential energy of the particles to overcome electrostatic forces rather than increasing their kinetic energy.

What formula calculates the thermal energy change when a substance changes temperature?

$E = m c \Delta T$, where $m$ is mass, $c$ is specific heat capacity (SHC), and $\Delta T$ is the temperature change.

What formula calculates the energy change during a change of state, and what is the specific latent heat of fusion for water?

$E = m L$ (mass times specific latent heat), where the specific latent heat of fusion for water is $334,000\,\text{J/kg}$.

How are pressure and volume related when a gas is compressed or expanded at constant temperature?

Pressure and volume are inversely proportional: $P \times V = \text{constant}$, meaning $P_1 V_1 = P_2 V_2$.

What is the formula and standard unit for surface pressure?

$\text{pressure} = \frac{\text{force}}{\text{area}}$ ($P = \frac{F}{A}$), measured in $\text{N/m}^2$ or pascals ($\text{Pa}$).

What equation calculates pressure at depth underwater, and what is the density of water?

$P = h \rho g$ (height/depth $\times$ density $\times$ gravitational field strength), where the density of water is $1,000\,\text{kg/m}^3$.

Why does atmospheric pressure decrease with increasing altitude?

The atmosphere becomes less dense at higher altitudes, meaning there is less weight of air pushing down.

What is the fundamental difference between a vector and a scalar quantity?

A scalar has magnitude only, while a vector has both magnitude and direction.

What does Newton's first law of motion state?

When there is no resultant force on an object, its motion remains constant (it remains stationary or moves at a constant velocity).

What is inertia?

The tendency of an object's motion to remain constant unless acted upon by a resultant force.

How is weight calculated, and what is the value of gravitational field strength ($g$) on Earth?

$\text{weight} = \text{mass} \times g$, where $g$ on Earth is $9.8\,\text{N/kg}$ (sometimes rounded to $10\,\text{N/kg}$).

What is the equation for work done by a force?

$\text{work done} = \text{force} \times \text{distance moved}$ ($W = F \times d$).

What does Hooke's law state, and what is its equation?

Force and extension are directly proportional for elastically deformed objects, expressed as $F = k e$, where $k$ is the spring constant.

How can parallax error be avoided when measuring a spring's extension against a ruler?

View the measurement at eye level with the bottom of the spring and line up the ruler's zero mark with the bottom of the unstretched spring.

What is a moment, and how is it calculated?

A moment is a turning force calculated as force multiplied by perpendicular distance to the pivot ($M = F \times d$), measured in $\text{N\,m}$.

What is the principle of moments?

For an object in balance (not turning), the total clockwise moments are equal to the total anticlockwise moments.

What do the gradients of a distance-time graph and a velocity-time graph represent?

The gradient of a distance-time graph represents speed/velocity, while the gradient of a velocity-time graph represents acceleration.

How is distance or displacement determined from a velocity-time graph?

By calculating the area under the velocity-time graph.

What quantities do the letters in the acronym 'suvat' represent?

$s$ is displacement, $u$ is initial velocity, $v$ is final velocity, $a$ is acceleration, and $t$ is time.

What is Newton's second law of motion in equation form?

$F = m a$ (resultant force equals mass times acceleration).

In the trolley acceleration practical for Newton's second law, why must masses removed from the hanger be added to the trolley?

Because the hanging weight accelerates the entire system (trolley plus masses), so mass must be moved rather than discarded to keep total mass constant.

What does Newton's third law of motion state?

For every action (force), there is an equal and opposite reaction force acting on the other object.

Why does doubling the speed of a car quadruple its braking distance?

Kinetic energy is proportional to the square of velocity ($E_k = \frac{1}{2} m v^2$), so doubling $v$ requires four times the energy to be dissipated by the brakes.

What is the formula and standard unit for momentum?

$\text{momentum} = \text{mass} \times \text{velocity}$ ($p = m v$), measured in $\text{kg\,m/s}$.

How does the formula $F = \frac{\Delta p}{t}$ explain the effectiveness of airbags, seat belts, and crumple zones?

They increase the time ($t$) over which the momentum is lost, which decreases the rate of change of momentum and reduces the force ($F$) experienced.

What is the definition of potential difference (voltage), and what is its equation?

Potential difference is the energy transferred per coulomb of charge: $V = \frac{E}{Q}$, where $1\,\text{V} = 1\,\text{J/C}$.

What is electric current, and what equation relates it to charge and time?

Current is the rate of flow of charge: $I = \frac{Q}{t}$ (rearranged as $Q = I t$), measured in amperes ($\text{A}$).

How are ammeters and voltmeters connected in a circuit?

An ammeter is connected in series with the component, whereas a voltmeter is connected in parallel across the component.

What is Ohm's law, and what defines an ohmic component?

$V = I R$. An ohmic component has constant resistance, resulting in a straight-line $I\text{-}V$ graph through the origin where current and voltage are directly proportional.

Why does the electrical resistance of a filament lamp increase at higher currents?

Higher currents cause more frequent collisions between delocalized electrons and lattice ions; this heats the metal and causes ions to vibrate more, hindering electron flow.

How does an electrical diode regulate current flow?

It permits current to flow in only one direction; resistance is very high in reverse and drops sharply to allow current flow at around $1\,\text{V}$ in the forward direction.

What are the rules for potential difference, current, and resistance in a series circuit?

Total potential difference is shared between components, current is identical through all components, and total resistance is the sum of the individual resistances.

What are the rules for potential difference, current, and resistance in a parallel circuit?

Potential difference is the same across all branches, total current is shared between branches, and adding resistors in parallel decreases total resistance.

How does temperature affect the resistance of a thermistor?

An increase in temperature causes the resistance of a thermistor to decrease.

How does light intensity affect the resistance of a light dependent resistor (LDR)?

An increase in light intensity causes the resistance of an LDR to decrease.

What are three elements that are naturally magnetic?

Iron, cobalt, and nickel.

What is a solenoid, and how can its magnetic field strength be increased?

A solenoid is a coil of wire that generates a magnetic field like a bar magnet; its strength increases by increasing the current or adding more turns of wire.

What is the motor effect equation for a wire perpendicular to a magnetic field?

$F = B I L$, where $F$ is force ($\text{N}$), $B$ is magnetic flux density ($\text{T}$), $I$ is current ($\text{A}$), and $L$ is length of wire ($\text{m}$).

In Fleming's left-hand rule, what do each of the three fingers represent?

Thumb represents Force (motion), First finger represents Magnetic Field (North to South), and Middle finger represents Current (positive to negative).

What is the function of a split ring commutator in a DC electric motor?

It reverses the direction of the current through the coil every half-turn to keep the motor spinning in the same direction.

What is the generator effect?

The induction of a potential difference (and current in a complete circuit) across a wire when it moves through a magnetic field or experiences a changing magnetic field.

Why must transformers operate on alternating current (AC) rather than direct current (DC)?

AC produces a continuously changing magnetic field in the iron core, which is required to induce a potential difference in the secondary coil; DC produces a static field.

Why does the National Grid step up voltage for long-distance power transmission?

Stepping up voltage decreases the current ($P = V I$), which significantly reduces energy dissipated as heat due to cable resistance.

What equation relates the coil turns and voltages in a transformer?

$\frac{N_p}{N_s} = \frac{V_p}{V_s}$, where $N_p$ and $N_s$ are turns on the primary and secondary coils, and $V_p$ and $V_s$ are primary and secondary voltages.