# List of Common Misconceptions

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This page is based on research by the Comprehensive Conceptual Curriculum for Physics Project.

# General

• History is irrelevant in science

# Atoms

• There is only one correct model of the atom.
• Electrons orbit the nucleus like planets around the Sun.
• Hydrogen is a typical atom.
• Electrons are physically larger than protons.

# Electricity

• Positive and negative are absolute, not arbitrary.
• High voltage by itself is dangerous.
• Voltage is the same as energy.
• Capacitors and batteries operate on the same principle.
• No potential difference exists in between the plates of a capacitor, only on the plates themselves.
• There is a net charge on a capacitor.
• Resistors consume charge.
• Electrons move around a circuit at the speed of light.
• A conductor has no resistance.
• Current gets used up as it flows around a circuit.

## Alternating Current

• Charges move all the way around a circuit and all the way back.
• Energy is not lost in a transformer.
• Electrical companies supply electrons.

# Energy

• Energy is "used up", "runs out" or can be "destroyed".
• Something not moving has no energy.
• Energy can be recycled.
• Energy is a force.
• When an object is released all its gravitational potential energy is instantly converted to kinetic energy.

## Temperature

• A cold body contains no heat.
• There is no limit on the lowest temperature.
• An object has no mass at absolute zero.
• A coat or jumper actually makes you warmer.
• Heat and cold can flow like liquids.
• Heat and temperature are the same thing.

# Fields

• Field lines are real.
• Field lines can begin and end anywhere.
• There are a limited number of field lines.
• Field lines only exist in two dimensions.
• A moving charge accelerates along a field line.

# Forces

• All forces must be contact forces.
• A force is required to maintain constant velocity; all objects will eventually come to a halt if the force is removed.
• Action-reaction pairs act on the same body.
• Acceleration causes a force (rather than vice versa).
• Friction cannot act in the direction of motion.
• Equilibrium is a consequence of Newton's Third Law.
• Only living things (e.g. people, animals) exert forces. Inanimate things (e.g. tables, floors) do not.
• A force applied by one object to another (e.g. a hand to a ball) still acts on the object once contact ceases (e.g. after the ball leaves the hand).

## Fundamental Forces and Interactions

• The gravitational force is the strongest.
• Electricity and magnetism are two different forces.
• All forces are equally effective over all ranges.
• None of the fundamental forces have been proven to exist.

# Gravity

• Gravity does not exist in a vacuum (i.e. it is a property of matter) or does not exist in space.
• Without gravity, all objects are equally easy to move.
• Weightlessness means that there is no gravity.
• Gravity on Earth is caused by the spinning of the Earth.
• The sudden removal of a gravitational field would cause objects to float "upwards".

## Falling Objects

• Heavier objects fall faster than light objects.
• Heavier objects accelerate faster than light objects.
• Gravity only acts on an object when it is falling.

## Orbits

• The Moon is not falling; or is not in free fall.
• The force acting on the Moon is somehow different to the force acting on a falling apple.
• There are no gravitational forces acting on an object in orbit (e.g. the Space Shuttle).
• Planetary orbits are circular.
• The speed of a planet in orbit is constant.
• Some object must be at both foci of an elliptical orbit.
• All planets orbit at the same speed.
• All planets orbit in exactly the same plane.

# Magnetism

• North and South poles are the same as positive and negative charges.
• Magnetic field lines begin and end at magnetic poles.
• Magnetic poles can be isolated.
• Magnetic fields are two-dimensional.
• A released charge will drift towards a magnetic pole.

# Motion

## Speed and Acceleration

• Two objects side-by-side have the same speed.
• Acceleration and velocity are always in the same direction.
• Velocity is a force.
• If velocity is zero, acceleration is zero.

## Momentum

• Conservation of momentum only applies in collisions.
• Momentum is the same as force.
• Momentum is the same as kinetic energy.

## Circular Motion

• Circular motion does not require a force.
• Centrifugal forces are real forces.
• An object moving in a circle at constant speed is also at constant velocity; i.e. experiences no acceleration.
• An object moving in a circle will continue to move in a circle when released; or will fly out radially.

## Harmonic Motion

• Period of oscillation depends on amplitude.
• The heavier the pendulum bob, the faster the oscillation.

# Relativity

• Time is absolute.
• Length and time only change for one observer.
• Time dilation refers to two different clocks in two different frames.
• Relativity is theoretical and is not supported by experimental evidence.
• There exists a "preferred" reference frame for the Universe.
• A mass moving at the speed of light becomes energy.

# Space

## Navigating in Space

• Spacecraft travel in straight lines.
• Jets can fly in space.
• Rockets require something (e.g. air) to push against.

## Black Holes

• Black holes are big.
• Light always travels in straight lines.
• If the Sun became a black hole Earth would be destroyed; black holes exert larger forces than their parent stars.
• Objects in space make sounds.

# Waves

• Waves transfer matter.
• All waves require a medium.
• Waves do not have energy.
• Different colours are different types of waves.

## Light

• Light has no origin.
• Light is a mixture of waves and particles.
• The speed of light never changes.
• Light and matter do not interact.
• Refraction is the bending of waves.

## Wave-Particle Duality

• Light is either a wave or a particle.
• Particles cannot have wave properties and vice versa.
• All photons have the same energy.