4.8.8

Parallel Circuits - Resistance

Test yourself on Parallel Circuits - 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 resistances 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.
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1

Motion, Forces & Energy

1.1

Physical Quantities & Measurement Techniques

1.1.1Measuring Length1.1.2Measuring Volume1.1.3Measuring Time1.1.4Scalar & Vector Quantities1.1.5Adding Vectors
1.2

Motion

1.2.1Average Speed1.2.2Calculating Average Speed1.2.3Velocity1.2.4Acceleration1.2.5Distance-Time Graphs1.2.6Speed-Time Graphs1.2.7More Speed-Time Graphs1.2.8Calculating Uniform Acceleration1.2.9Gravity1.2.10Free Fall - Distance-Time & Speed-Time Graphs1.2.11Air Resistance1.2.12Air Resistance - Graphs1.2.13Optional: Calculating Acceleration
1.3

Mass & Weight

1.3.1Mass1.3.2Weight1.3.3Gravity Calculations
1.4

Density

1.4.1Density1.4.2Equation for Density1.4.3Density - Experiments1.4.4Density - Calculations
1.5

Forces: Effects of Forces

1.5.1Spring Constant1.5.2Spring Constant Equation1.5.3Force & Acceleration1.5.4Friction
1.6

Forces: Turning Effects of Forces

1.6.1Circular Motion1.6.2Turning Effect1.6.3Moments1.6.4Calculating Moments
1.7

Forces: Centre of Gravity

1.7.1Equilibrium1.7.2Centre of Gravity1.7.3Centre of Gravity Experiment
1.8

Momentum

1.8.1Momentum
1.9

Energy, Work, & Power: Energy

1.9.1Energy Changes1.9.2Energy Conversion1.9.3Kinetic Energy Stored1.9.4Calculating Changes in Kinetic Energy1.9.5Gravitational Potential Energy Stored1.9.6Calculating Changes in GPE1.9.7Elastic Potential Energy Stored1.9.8Calculating Changes in EPE
1.10

Energy, Work & Power: Work

1.10.1Mechanical Work1.10.2Calculating Mechanical Work1.10.3Calculating Electrical Work Done
1.11

Energy, Work & Power: Energy Resources

1.11.1Energy Resources1.11.2Fossil Fuels1.11.3Geothermal Energy1.11.4Wind Energy1.11.5Water Energy1.11.6Tidal Energy1.11.7Nuclear Energy1.11.8Solar Energy1.11.9Original Source of Energy1.11.10Fusion1.11.11Efficiency1.11.12Calculating Efficiency1.11.13Energy Wastage
1.12

Energy, Work & Power: Power

1.12.1Power
1.13

Pressure

1.13.1Pressure1.13.2Atmospheric Pressure1.13.3Calculating Pressure1.13.4Liquid Pressure1.13.5Manometer1.13.6Calculating Liquid Pressure
2

Thermal Physics

2.1

Kinetic Particle Model of Matter

2.1.1Kinetic Particle Model of Matter2.1.2States of Matter2.1.3Properties of Gases
2.2

Thermal Properties & Temperature

2.2.1Thermal Expansion2.2.2Changes in Internal Energy2.2.3Heat Capacities2.2.4Heat Capacities Experiment2.2.5Internal Energy2.2.6Calculating Internal Energy2.2.7End of Topic Test - Thermal Physics2.2.8Changes of State2.2.9Evaporation2.2.10Factors Affecting Evaporation2.2.11Examples of Evaporation
2.3

Transfer of Thermal Energy

2.3.1Conduction2.3.2Molecular Conduction2.3.3Convection Currents2.3.4Radiation2.3.5Surface Colour2.3.6Emitting Radiation2.3.7Leslie's Cube & Other Radiation Experiments2.3.8Uses of Energy Transfer
3

Waves

3.1

General Properties of Waves

3.1.1Wave Basics3.1.2Transverse Wave3.1.3Longitudinal Wave3.1.4Ripple Tank3.1.5Wave Speed3.1.6Wave Speed Formula3.1.7Calculating Wave Speed3.1.8Wave Frequency3.1.9Calculating Wave Frequency3.1.10Wavelength3.1.11Diffraction
3.2

Light: Reflection & Refraction

3.2.1Reflection3.2.2Internal Reflection3.2.3Refraction3.2.4More Refraction3.2.5Refractive Index Equation3.2.6Refractive Index3.2.7Critical Angle3.2.8Optical Fibres3.2.9Optical Fibres in Communications3.2.10Medical Applications of Optical Fibres
3.3

Light: Thin Lenses

3.3.1Thin Converging Lenses 13.3.2Thin Converging Lens 23.3.3Thin Converging Lens 33.3.4Thin Converging Lens 43.3.5Calculating Lenses
3.4

Light: Dispersion of Light

3.4.1Dispersion of Light3.4.2Triangular Prisms 13.4.3Triangular Prisms 2
3.5

Electromagnetic Spectrum

3.5.1Properties of Electromagnetic Waves3.5.2Gamma Rays3.5.3X-Rays3.5.4UV Light3.5.5Visible Light3.5.6Infrared Radiation3.5.7Microwaves3.5.8Radio Waves3.5.9Other Uses of EM Waves3.5.10Analogue & Digital Signals
3.6

Sound

3.6.1Sound Waves3.6.2Ears3.6.3Speed of Sound3.6.4Measuring Sound Waves3.6.5Oscilloscope Traces3.6.6Sound Waves Experiment
4

Electricity & Magnetism

4.1

Simple Phenomena of Magnetism

4.1.1Magnets4.1.2Magnetic Forces4.1.3Magnetic Materials4.1.4Induced Magnetism4.1.5Temporary & Permanent Magnets4.1.6Electromagnets4.1.7Magnetic Field Lines
4.2

Electrical Quantities: Electric Charge

4.2.1Electrical Charge4.2.2Charged Objects4.2.3Static Electricity Experiments4.2.4Charging by Induction4.2.5Electric Fields4.2.6Electric Field Patterns4.2.7Conductors4.2.8Electrical Conductors - Electrons
4.3

Electrical Quantities: Electric Current

4.3.1Current4.3.2Conventional Current4.3.3Current Equation4.3.4Calculating Current4.3.5AC/DC
4.4

Electromotive Force & Potential Difference

4.4.1Electromotive Force4.4.2Potential Difference4.4.3Potential Difference Equation4.4.4Calculating Voltage
4.5

Electrical Quantities: Resistance

4.5.1Circuit Measurements4.5.2Resistance4.5.3Equation for Resistance4.5.4Measuring Resistance4.5.5Calculating Resistance & Ohm's Law4.5.6Variable Resistance4.5.7Resistance Graph
4.6

Electrical Energy & Electrical Power

4.6.1Electrical Work4.6.2Electrical Power4.6.3Calculating Electrical Work
4.7

Electric Circuits: Circuit Diagrams & Components

4.7.1Circuit Diagrams4.7.2Circuit Symbols4.7.3More Circuit Symbols4.7.4Diodes4.7.5LDRs & Thermistors
4.8

Electric Circuits: Series & Parallel Circuits

4.8.1Series Circuits4.8.2Series Circuits - Resistors4.8.3Series Circuits - Cells4.8.4Series Circuits - Potential Difference4.8.5Calculating Series Circuits4.8.6Parallel Circuits4.8.7Parallel Circuits - Current4.8.8Parallel Circuits - Resistance4.8.9Parallel Circuits in Practice
4.9

Electric Circuits: Action & Use

4.9.1Potentiometer4.9.2Potential Divider Equation
4.10

Electrical Safety

4.10.1Dangers of Electricity4.10.2Live & Neutral Wires4.10.3Earthing Metal Cases4.10.4Fuses & Trip Switches4.10.5Fuse Ratings
4.11

Electromagnetic Effects: Electromagnetic Induction

4.11.1Electromagnetic Induction4.11.2Size of e.m.f4.11.3Forces Between Electricity & Magnets4.11.4Rotation of Coil & Induced e.m.f
4.12

Electromagnetic Effects: The A.C. Generator

4.12.1The Rotating-Coil Generator4.12.2Features of a Rotating-Coil Generator
4.13

Magnetic Effect of a Current

4.13.1Magnetic Effect of a Current4.13.2Solenoid Field4.13.3Relays
4.14

Force on a Current-Carrying Conductor

4.14.1Magnetic Field Strength4.14.2Uses of Magnets & Currents4.14.3Catapult Experiment4.14.4Beam Force Experiment
4.15

Electromagnetic Effects: The D.C. Motor

4.15.1Motor Effect4.15.2Direction of Motor Effect4.15.3DC Motors4.15.4Coil of Wire in a Magnetic Field
4.16

Electromagnetic Effects: The Transformer

4.16.1Transformers4.16.2Transformers Equation4.16.3Types of Transformer4.16.4Principles of Transformer Operation4.16.5Energy in Transformers
5

Nuclear Physics

5.1

The Nuclear Model of the Atom

5.1.1Atomic Model5.1.2Scattering of Alpha Particles5.1.3Subatomic Particles5.1.4Proton & Nucleon Numbers5.1.5Calculating Number of Neutrons5.1.6Isotopes5.1.7More Isotopes5.1.8Carbon Nuclides5.1.9Nuclear Fusion5.1.10Nuclear Fission5.1.11More Nuclear Fission
5.2

Radioactivity: Detection of Radioactivity

5.2.1Radioactivity5.2.2Types of Radiation5.2.3Detection of Radioactivity5.2.4Background Radiation
5.3

Radioactivity: The Three Types of Nuclear Emission

5.3.1Three Types of Emission5.3.2Relative Ionising Effects5.3.3Electric Fields5.3.4Magnetic Fields Radiation
5.4

Radioactive Decay

5.4.1Radioactive Decay5.4.2Decay Equations5.4.3Half Life5.4.4Measuring Half-Life5.4.5Practical Applications of Radiation5.4.6Ionising Radiation5.4.7Safety Precautions
6

Space Physics

6.1

The Earth & the Solar System

6.1.1The Earth6.1.2The Moon6.1.3The Solar System & The Accretion Model6.1.4Gravitational Field & Speed of Light6.1.5The Sun's Gravitational Field
6.2

Stars & the Universe

6.2.1The Sun as a Star6.2.2Galaxies6.2.3Life Cycle of a Star like the Sun6.2.4Life Cycle of a Star Much Bigger than the Sun6.2.5Creation of Elements6.2.6Red-shift6.2.7The Big Bang6.2.8Cosmic Microwave Background Radiation6.2.9The Hubble Constant

Practice questions on Parallel Circuits - Resistance

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

  1. 1
    Which of the following combinations has the largest total resistance?Multiple choice
  2. 2
    Which of the following are true of resistance in parallel circuits?True / false
  3. 3
    What happens to the combined resistance when two resistors are connected in parallel?Multiple choice
  4. 4
    What analogy is used to explain the concept of resistors in parallel?Multiple choice
  5. 5
    According to the reciprocal rule, how can the total resistance be calculated when two resistors are connected in parallel?Multiple choice
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Parallel Circuits - Current

Parallel Circuits in Practice