Key ideas in physics common mistakes

Energy is used up

Saying energy is used up.

Say energy is transferred, stored or dissipated; conservation still applies.

Current and potential difference are the same

Treating current as the same quantity as potential difference.

Current is rate of flow of charge; potential difference is energy transferred per charge.

Mass and weight mean the same thing

Using mass and weight interchangeably.

Mass is measured in kg; weight is a force in N caused by a gravitational field.

Speed and velocity are identical

Ignoring direction when discussing velocity.

Speed is scalar; velocity includes direction.

Reflection and refraction are interchangeable

Describing bending at a boundary as reflection.

Reflection is bouncing back; refraction is changing direction because speed changes at a boundary.

A generator is just a motor

Confusing the motor effect with electromagnetic induction.

Motors use current in a magnetic field to produce force; generators induce potential difference from motion.

Red shift is the Big Bang

Calling red shift the Big Bang theory.

Red shift is evidence for expansion; the Big Bang is the explanatory model.