State the apparatus needed to verify the rules for resistors in series and in parallel.

A low-voltage d.c. supply or battery, at least two resistors of known nominal value, connecting leads, a switch, an ammeter and a voltmeter, together with an ohmmeter or multimeter for checking the resistor values.

Which electrical quantity is the same at every point in a series circuit, and how would you confirm it experimentally?

The current is the same everywhere, which is confirmed by moving the ammeter to different positions in the series loop and showing that the reading does not change.

Which electrical quantity is the same across every branch of a parallel combination, and how would you confirm it experimentally?

The potential difference is the same across each branch, which is confirmed by connecting a voltmeter across each resistor in turn and finding the same reading each time.

How must the ammeter and the voltmeter be placed when measuring the resistance of a combination of resistors?

The ammeter is placed in series so that the whole current to be measured passes through it, and the voltmeter is placed in parallel across the combination whose potential difference is being measured.

CCEA A-Level Physics 1210

Physical Quantities, Scalars and Vectors

Topic overview Physical quantities and SI base units Prefixes and standard form Scalars and vectors Resolving vectors and finding resultants Coplanar forces in equilibrium

Moments and Equilibrium

Topic overview Moment of a force Centre of gravity The principle of moments Determining unknown masses using moments

Linear Motion and Dynamics

Topic overview Displacement, velocity and acceleration The equations of motion for uniform acceleration Measuring the acceleration of free fall with light gates Displacement–time and velocity–time graphs Projectile motion Projectile calculations

Newton's Laws of Motion

Topic overview Newton's first law and inertia Newton's second law and F = ma Applying Newton's laws to simple situations Newton's third law Friction as a force opposing motion

Linear Momentum and Impulse

Topic overview Momentum and its calculation Conservation of linear momentum Collisions in one dimension Elastic and inelastic collisions Impulse and the impulse–momentum equation Impacts and reducing the force of a collision Newton's second law in terms of momentum

Work, Energy and Power

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Current, Charge and Potential Difference

Topic overview Electric current and the coulomb Potential difference and energy transfer Potential difference, power and current Electromotive force Comparing electromotive force and potential difference

Resistance and Resistivity

Topic overview Resistance and Ohm's law Ohmic and non-ohmic behaviour Resistors in series and in parallel Investigating current, voltage and resistance in series and parallel circuits Electrical power and energy in resistive circuits Resistivity and the equation R = ρl/A Measuring the resistivity of a metal Current–voltage characteristics of a conductor, a lamp and a diode Resistance, temperature and superconductivity

Internal Resistance and Potential Dividers

Topic overview Internal resistance and terminal potential difference Consequences of internal resistance for external circuits Measuring electromotive force and internal resistance The potential divider and variable output Potential dividers in lighting and heating control circuits Loaded potential dividers and output voltage calculations

Waves

Topic overview Transverse and longitudinal waves Amplitude, period, frequency and wavelength Phase and phase difference Reading wave graphs The wave equation Polarisation The electromagnetic spectrum

Refraction

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Lenses

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Wave-Particle Duality

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Astronomy

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Practical Skills and Data Analysis

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Deformation of Solids

Topic overview Hooke's law and the spring constant Elastic and plastic deformation and the elastic limit Stress, strain and the Young modulus Measuring the Young modulus of a wire Strain energy and force–extension graphs Choosing materials: strength, stiffness and cost

Thermal Physics

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Uniform Circular Motion

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Simple Harmonic Motion

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The Nucleus and Radioactive Decay

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Nuclear Energy, Fission and Fusion

Topic overview Mass–energy equivalence and E = Δmc² Mass defect and binding energy The binding energy per nucleon curve Inside a fission reactor Nuclear power: social, environmental, security and economic issues The ITER tokamak fusion reactor Plasma confinement: gravitational, inertial and magnetic

Gravitational Fields

Topic overview Fields of force and field lines Gravitational field strength Newton's law of universal gravitation The field strength of a point mass Circular motion of planets and satellites Kepler's third law Geostationary satellites

Electric Fields

Topic overview Electric field strength Coulomb's law The field of a point charge Uniform fields between parallel plates Comparing gravitational and electric fields Field strength calculations and combined fields

Capacitors

Topic overview Capacitance and the farad Energy stored in a charged capacitor Capacitors in series and in parallel Charging and discharging a capacitor The exponential decay equations The time constant Flash guns and defibrillators Uses of capacitors in circuits Capacitor calculations and graph work

Magnetic Fields

Topic overview Magnetic fields around currents The force on a current-carrying conductor Magnetic flux density The electric motor Magnetic flux and flux linkage Faraday's law of electromagnetic induction Lenz's law The alternating current generator Transformers Power losses and high-voltage transmission

Charged Particles and Accelerators

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Fundamental Particles

Topic overview Fundamental particles The four fundamental forces Classifying particles Quarks and the structure of hadrons Conservation laws Beta decay in the quark model

Resistance and Resistivity

Investigating current, voltage and resistance in series and parallel circuits

3 things to know
Unit AS 1

Overview

Recall questions on the apparatus and method for verifying the series and parallel rules, which quantity is common in each arrangement, where the ammeter and voltmeter go, why the current is kept small and the circuit switched off between readings, the junction rule, and the systematic error the meters themselves introduce.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Describe how to verify experimentally that resistances add when resistors are connected in series.

Key term

Describe how to verify experimentally the rule for resistors connected in parallel.

Key term

When verifying the series and parallel resistor rules, why should the current be kept small and the circuit switched off between readings?

Questions from this subtopic

Each one with the model answer underneath.

1
State the apparatus needed to verify the rules for resistors in series and in parallel.
Model answer
A low-voltage d.c. supply or battery, at least two resistors of known nominal value, connecting leads, a switch, an ammeter and a voltmeter, together with an ohmmeter or multimeter for checking the resistor values.
2
Describe how to verify experimentally that resistances add when resistors are connected in series.
Model answer
Measure each resistor separately with an ohmmeter, connect them in series with an ammeter and a supply, measure the current and the total potential difference across the combination, calculate the total resistance from V/I and compare it with the sum of the individual values.
3
Describe how to verify experimentally the rule for resistors connected in parallel.
Model answer
Measure each resistor separately, connect them in parallel across the supply with an ammeter reading the total current, measure the potential difference across the combination, find the total resistance from V/I and compare it with the value predicted by the sum of the reciprocals.
4
Which electrical quantity is the same at every point in a series circuit, and how would you confirm it experimentally?
Model answer
The current is the same everywhere, which is confirmed by moving the ammeter to different positions in the series loop and showing that the reading does not change.
5
Which electrical quantity is the same across every branch of a parallel combination, and how would you confirm it experimentally?
Model answer
The potential difference is the same across each branch, which is confirmed by connecting a voltmeter across each resistor in turn and finding the same reading each time.
6
How must the ammeter and the voltmeter be placed when measuring the resistance of a combination of resistors?
Model answer
The ammeter is placed in series so that the whole current to be measured passes through it, and the voltmeter is placed in parallel across the combination whose potential difference is being measured.

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