2.3.8

Parallel Resistance

Test yourself on Parallel Resistance

Test your knowledge with free interactive questions on Seneca — used by over 10 million students.

Resistance

The combined resistance of two resistors in parallel is less than the resistance of either of the two resistors by themselves.

Like water draining through a bucket

Like water draining through a bucket

Consider a bucket full of water with a hole in the bottom:
- Water drains out of the bucket.
- If a second hole is drilled into the bucket the water (like adding another resistor in parallel) will drain faster.
- It does not matter how narrow the second hole is (how high its resistance is), it is always faster for water to flow through two holes instead of one.

1

Energy

1.1

Energy Changes

1.2

Energy 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

1.3

Energy 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

2

Electricity

2.1

Electric 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

2.2

Resistance & 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

2.3

Electric 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

2.4

Electricity 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

2.5

Static 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

3

Particle Model of Matter

3.1

States 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

3.2

Heat

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

3.3

Particle 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

4

Atoms & Radiation

4.1

Atoms

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

4.2

Radiation

5

Forces

5.1

Basics 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

5.2

Forces

5.3

Effects of Forces

5.4

Pressure

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

6

Waves

6.1

Wave 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

6.2

Waves 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

6.3

Sound 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

6.4

Electromagnetic 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

6.5

Lenses

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

6.6

Heat & 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

7

Magnetism

7.1

Magnetism Basics

7.1.1Magnetism 7.1.2Magnetic Materials 7.1.3Induced Magnetism 7.1.4Magnetic Fields 7.1.5Magnetic Field Patterns

7.2

Electromagnetism

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

7.3

Transformers

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

8

Astrophysics

8.1

Astrophysics

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

1

Energy

1.1

Energy Changes

1.2

Energy 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

1.3

Energy 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

2

Electricity

2.1

Electric 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

2.2

Resistance & 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

2.3

Electric 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

2.4

Electricity 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

2.5

Static 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

3

Particle Model of Matter

3.1

States 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

3.2

Heat

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

3.3

Particle 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

4

Atoms & Radiation

4.1

Atoms

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

4.2

Radiation

5

Forces

5.1

Basics 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

5.2

Forces

5.3

Effects of Forces

5.4

Pressure

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

6

Waves

6.1

Wave 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

6.2

Waves 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

6.3

Sound 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

6.4

Electromagnetic 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

6.5

Lenses

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

6.6

Heat & 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

7

Magnetism

7.1

Magnetism Basics

7.1.1Magnetism 7.1.2Magnetic Materials 7.1.3Induced Magnetism 7.1.4Magnetic Fields 7.1.5Magnetic Field Patterns

7.2

Electromagnetism

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

7.3

Transformers

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

8

Astrophysics

8.1

Astrophysics

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

Practice questions on Parallel Resistance

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

1
Which of the following combinations has the largest total resistance?Multiple choice
2
Which bucket will leak water faster?Multiple choice
3
Which of the following are true of resistance in parallel circuits?True / false
4
What happens to the combined resistance when two resistors are connected in parallel?Multiple choice
5
What analogy is used to explain the concept of resistors in parallel?Multiple choice

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Parallel Current

Lights in Parallel