Required Practical - Investigating Resistance

Test yourself

Investigating Factors that Affect Resistance in Circuits

The aim of this experiment is to explore how the resistance of a wire changes when its length is altered.

Apparatus

Power supply (low voltage, e.g. 1.5 - 3 V)
Ammeter and voltmeter
Resistance wire (e.g. nichrome)
Metre ruler
Crocodile clips and connecting leads
Switch

Method

Build the circuit using a power supply, ammeter, voltmeter, and the resistance wire.
Connect two crocodile clips to the thin resistance wire, 100 cm apart.
Switch the circuit on and record both current and potential difference.
Move one clip to reduce the length of wire between clips by 10 cm each time.
For each length, record the new voltage and current readings.
Use $R=\frac{V}{I}$ to calculate resistance for each length.

Results & Analysis

The resistance increases with wire length.
The relationship should be directly proportional (a straight line through the origin).
Plot a graph of resistance (on the y-axis) against length (on the x-axis) and draw a line of best fit.

Hazards & Safety

Heating of wire burns skin:
- Avoid touching the wire when the circuit is on; allow time for cooling.
Mild electric shock:
- Use a low-voltage supply and keep equipment dry.

Investigating Factors that Affect Resistance in Circuits 2

This experiment aims to explore how the total resistance of a circuit changes when resistors are connected in series and when they are connected in parallel.

Apparatus

Power supply (around 4 V)
Ammeter
Voltmeter
Two fixed-value resistors (R₁ and R₂)
Connecting wires and crocodile clips
Switch

Variables

Independent variable:
- The way the resistors are connected (single, series, or parallel)
Dependent variable:
- Total resistance of the circuit
Control variables:
- Voltage of the power supply
- Type and temperature of resistors used

Method - Single Resistor Test

Build a simple circuit with the power supply, one resistor (R₁), an ammeter in series, and a voltmeter across the resistor.
Close the switch and record the readings of current and potential difference.
Repeat with the second resistor (R₂).

Method - Series and Parallel

Series:
- Reconnect the circuit with both resistors joined in series.
- Keep the voltmeter in parallel across both resistors together.
- Record the current and voltage once the switch is closed.
Parallel:
- Rearrange the resistors so that R₁ and R₂ are in parallel.
- Ensure the voltmeter is connected across both resistors.
- Take the new current and voltage readings
For every setup, calculate total resistance using the formula: $R=\frac{V}{I}$

Results and Analysis

In Series:
- The total resistance increases and equals the sum of both resistors: $RTotal=R_1 +R_2$
- This happens because the current passes through each resistor in turn, so resistance adds up.
In Parallel:
- The total resistance is smaller than the smallest individual resistor: $\frac{1}{RTotal}=\frac{1}{R_1} +\frac{1}{R_2}$
- This is because the current splits into separate paths, allowing more total charge to flow.

Safety Precautions

Do not touch the resistors or wires while current is flowing–they can become very hot.
Turn off the power immediately if you notice burning smells or smoke.
Keep liquids away from the circuit to prevent short circuits or electric shocks.
Use low voltage to reduce the risk of overheating and ensure safe handling of the apparatus.

1Energy

1.1Energy Changes

1.2Energy Losses & Efficiency

1.2.1Energy Wastage

1.2.2Energy Efficiency

1.2.3Reducing Energy Loss

1.2.4Power & Energy Transfer

1.2.5Required Practical - Investigating Insulation

1.2.6Efficiency - Calculations

1.2.7Grade 9 - Energy & Efficiency

1.3Energy Resources

1.3.1Energy Resources

1.3.2Fossil Fuels

1.3.3Geothermal Energy

1.3.4Wind Energy

1.3.5Water Energy

1.3.6Tidal Energy

1.3.7Nuclear Energy

1.3.8Solar Energy

1.3.9Original Source of Energy

1.3.10Non-Renewable & Renewable Resources

1.3.11Uses of Energy Sources

1.3.12Changing Electricity Use

1.3.13Renewable Energy

1.3.14Limits to Renewable Energy Resources

1.3.15End of Topic Test - Energy

1.3.16Exam-Style Questions - Energy

2Electricity

2.1Electric Charge

2.1.1Circuit Diagrams

2.1.2Circuit Symbols

2.1.3Current

2.1.4Current Equation

2.1.5Current - Calculations

2.1.6Conductors

2.1.7Electrical Conductors - Electrons

2.1.8Potential Difference

2.1.9Voltage Equation

2.1.10Measurements in Circuit

2.1.11Voltage - Calculations

2.1.12Diagnostic Misconceptions - Powering a Circuit

2.2Resistance & Electrical Work

2.2.1Resistance

2.2.2Measuring Resistance

2.2.3Resistance Graph

2.2.4Diodes

2.2.5LDRs & Thermistors

2.2.6Electrical Work

2.2.7Power

2.2.8Ohm's Law

2.2.9Ohm's Law - Equation

2.2.10Resistance & Ohms Law - Calculations

2.2.11Electrical Work - Calculations

2.2.12Required Practical - Investigating Resistance

2.3Electric Circuits

2.3.1Series Circuits

2.3.2Resistors

2.3.3Required Practical - I–V Characteristics

2.3.4Cells in Series

2.3.5Series Circuits - Calculations

2.3.6Parallel Circuits

2.3.7Parallel Current

2.3.8Parallel Resistance

2.3.9Lights in Parallel

2.3.10Parallel Circuits - Calculations

2.3.11Grade 9 - Circuits

2.3.12Exam-Style Questions - Electricity

2.4Electricity in Homes

2.4.1AC/DC

2.4.2Mains Electricity

2.4.3Power Ratings

2.4.4National Grid

2.4.5Domestic Uses - Calculations

2.4.6Fuses & Circuit Breakers

2.4.7Fuse Ratings

2.4.8Earthing

2.4.9Dangers of the Live Wire

2.4.10End of Topic Test - Electricity

2.5Static Electricity

2.5.1Electrical Charge

2.5.2Charging an Object

2.5.3Charged Objects

2.5.4Static Electricity

2.5.5Electric Fields

2.5.6Field Diagrams

3Particle Model of Matter

3.1States of Matter

3.1.1Atomic Model

3.1.2Atomic Structure

3.1.3Sub-Atomic Particles

3.1.4Models of the Atom

3.1.5Alpha Particles

3.1.6Electron Arrangements

3.1.7Density

3.1.8Density Equation

3.1.9Density & the Particle Model

3.1.10Density - Calculations

3.1.11Changes of State

3.1.12Melting & Boiling

3.1.13Exam-Style Questions - Density

3.1.14Required Practical - Density

3.1.15Diagnostic Misconceptions - Floating

3.1.16Diagnostic Misconceptions - Volume

3.2Heat

3.2.1Internal Energy

3.2.2Change in Thermal Energy

3.2.3Required Practical - Specific Heat Capacity

3.2.4Equation for Heat Capacity

3.2.5Leslie's Cube

3.2.6Internal Energy - Calculations

3.2.7Melting & Boiling

3.2.8Latent Heat

3.2.9Energy Change for Change of State

3.2.10Latent Heat - Calculations

3.2.11Specific Latent Heat of Fusion

3.2.12Specific Latent Heat of Vaporisation

3.3Particle Motion in Gases

3.3.1States of Matter

3.3.2Properties of Gases

3.3.3Temperature Increase in a Gas

3.3.4Work Done on a Gas

3.3.5End of Topic Test - Particle Model of Matter

3.3.6Grade 9 - Particle Model of Matter

3.3.7Exam-Style Questions - Specific Heat Capacity

4Atoms & Radiation

4.1Atoms

4.1.1Atomic Model

4.1.2Structure of an Atom

4.1.3Sub-Atomic Particles

4.1.4Alpha Particles

4.1.5The Model of the Atom

4.1.6Electron Arrangements

4.1.7Proton & Nucleon Numbers

4.1.8Atoms & Ions

4.1.9Isotopes 1

4.1.10Isotopes 2

4.1.11Carbon Nuclides

4.1.12Exam-Style Questions - Atomic Structure

4.1.13Diagnostic Misconceptions - Types of Radiation

4.2Radiation

5Forces

5.1Basics of Motion

5.1.1Velocity

5.1.2Average Speed

5.1.3Adding Vectors

5.1.4Acceleration

5.1.5Distance vs Displacement

5.1.6Contact & Non-Contact Forces

5.1.7Contact Forces - Examples

5.1.8Distance-Time Graphs

5.1.9Speed-Time Graphs

5.1.10Velocity - Time Graph

5.1.11Average Speed - Calculations

5.1.12Acceleration - Calculations

5.1.13Uniform Acceleration - Calculations

5.1.14Grade 9 - Motion

5.1.15Exam-Style Questions - Motion

5.1.16Diagnostic Misconception - Motion

5.1.17Diagnostic Misconceptions - Acceleration

5.2Forces

5.3Effects of Forces

5.4Pressure

5.4.1Pressure & Force on Container

5.4.2Atmospheric Pressure

5.4.3Liquid Pressure

5.4.4Pressure - Calculations

5.4.5Liquid Pressure - Calculations

5.4.6Upthrust

5.4.7Depth Control of Submarine

5.4.8Pressure Difference

5.4.9End of Topic Test - Forces

5.4.10Exam-Style Questions - Pressure

6Waves

6.1Wave Basics

6.1.1Wave Basics

6.1.2Wave Speed Formula

6.1.3Wave Speed Equation

6.1.4Wave Speed - Calculations

6.1.5Wave Frequency Formula

6.1.6Wavelength & Amplitude

6.1.7Wave Frequency - Calculations

6.1.8Transverse Waves

6.1.9Longitudinal Wave

6.1.10Required Practical - Ripple Tank

6.1.11Diagnostic Misconceptions - Wavelength

6.2Waves at a Boundary

6.2.1Waves at a Boundary

6.2.2Waves at a Boundary 2

6.2.3Reflection of Light

6.2.4Refraction of Light

6.2.5Refraction of Light 2

6.2.6Internal Reflection

6.2.7Required Practical - Reflection and Refraction

6.3Sound Waves

6.3.1Sound Waves

6.3.2Sound Waves & our Ears

6.3.3Speed of Sound 1

6.3.4Speed of Sound 2

6.3.5Sound as a Wave

6.3.6Uses of Sound Waves: Ultrasound Waves

6.3.7Uses of Sound Waves: Earthquakes

6.3.8Sound Waves - Calculations

6.3.9End of Topic Test - Introduction to Waves

6.3.10Exam-Style Questions - Wave Speed

6.4Electromagnetic Waves

6.4.1Properties of Electromagnetic Waves

6.4.2Gamma Rays

6.4.3X-Rays

6.4.4UV Light

6.4.5Infrared Radiation

6.4.6Microwaves

6.4.7Radio Waves

6.4.8Properties 2

6.4.9Visible Light

6.4.10Visible Light 2

6.4.11Specular & Diffuse Reflection

6.4.12Colours

6.4.13Grade 9 - Waves

6.5Lenses

6.5.1Lenses

6.5.2Convex Lens

6.5.3Concave Lens

6.5.4Lenses - Calculations

6.5.5Images

6.5.6Ray Diagrams

6.5.7Ray Diagrams 2

6.6Heat & Radiation

6.6.1Infrared Radiation

6.6.2Radiation & Surface Colour

6.6.3Surface Area & Temperature

6.6.4Temperature

6.6.5Absorption & Emission

6.6.6Greenhouse Effect

6.6.7Energy Balance of the Earth

6.6.8End of Topic Test - EM Waves, Lenses & Heat

6.6.9Exam-Style Questions - EM Radiation

7Magnetism

7.1Magnetism Basics

7.1.1Magnetism

7.1.2Magnetic Materials

7.1.3Induced Magnetism

7.1.4Magnetic Fields

7.1.5Magnetic Field Patterns

7.2Electromagnetism

7.2.1The Magnetic Effect of a Current

7.2.2Solenoid Field

7.2.3Magnetic Field Strength

7.2.4Uses of Electromagnets

7.2.5Motor Effect

7.2.6Direction of Motor Effect

7.2.7Magnetic Flux Equation

7.2.8Magnetic Flux - Calculations

7.2.9Electric Motors

7.2.10Loudspeakers

7.2.11Force Acting on a Coil in a Magnetic Field

7.2.12Induced Potential Difference

7.2.13Increasing the Induced Potential Difference

7.2.14Magnetic Field Direction

7.2.15Forces Between Electricity & Magnets

7.2.16AC/DC

7.2.17AC Generators

7.2.18Generator Effect

7.2.19Microphones

7.3Transformers

7.3.1Transformers

7.3.2Transformer Equation

7.3.3Step-Up & Step-Down Transformers

7.3.4Principles of Transformer Operation

7.3.5High-Voltage Transmission & Transformers

7.3.6Energy in Transformers

7.3.7Power Losses in Cables

7.3.8Transformers - Calculations

7.3.9Transformers 2 - Calculations

7.3.10End of Topic Test - Magnetism

7.3.11Grade 9 - Transformers

7.3.12Exam-Style Questions - Magnetic Fields

8Astrophysics

8.1Astrophysics

8.1.1The Solar System

8.1.2The Sun

8.1.3The Solar System - Calculations

8.1.4Orbits

8.1.5Stable Orbits

8.1.6Orbits HyperLearning

8.1.7Life Cycle of a Star like the Sun

8.1.8Life Cycle of a Star Much Bigger than the Sun

8.1.9Creation of Elements

8.1.10Red-shift

8.1.11The Big Bang Theory

8.1.12Gaps in Knowledge

8.1.13End of Topic Test - Astrophysics

8.1.14Exam-Style Questions - Astrophysics

Jump to other topics