Leaving Cert Physics
32 guides on the parts of Leaving Cert Physics students reliably get wrong - the definitions that blur together, the steps that get skipped, and the reasoning an examiner expects to see. Each one names the mistake, explains why it happens, and gives you the correction.
Why Students Make Errors in Moving Charges and Magnetism
A moving charge creates a magnetic field, and a field pushes back on a moving charge. The two effects Leaving Cert Physics students merge.
Why Students Make Errors in Current Electricity
Current, potential difference and resistance are three different quantities, and swapping them is the most common Leaving Cert Physics circuit error.
Why Students Get Electrostatic Potential and Capacitance Wrong
Potential is not the same as potential energy, and capacitance is not charge. The electrostatics distinctions Leaving Cert Physics questions turn on.
Common Mistakes in Dimensional Analysis That Cost Marks
Checking units is the fastest way to catch a wrong answer before you hand it up. How unit checking works in Leaving Cert Physics calculations.
How to avoid errors when solving inelastic collision problems
Momentum is conserved in every collision, kinetic energy is not. Where Leaving Cert Physics students go wrong on inelastic collisions.
How to correctly apply Archimedes principle without confusion
Upthrust equals the weight of fluid displaced, not the weight of the object. Applying the principle without talking yourself out of it.
How to easily master ray diagrams for lenses and mirrors
Three rays, drawn in the right order, give the image every time. Ray diagrams for lenses and mirrors in Leaving Cert Physics.
How to easily understand capacitance and parallel plates
What capacitance actually measures, and why plate area and separation change it. Parallel plate capacitors for Leaving Cert Physics.
How to prevent errors in drawing free body diagrams
Draw only the forces acting on the body, and no others. The free body diagram habit that prevents most Leaving Cert Physics mechanics errors.
How to stop getting confused by right-hand rules in Magnetism
Which hand, which finger, which quantity. Sorting out the magnetism rules so they give the right direction under exam pressure.
How to stop making silly mistakes in simple harmonic motion
Acceleration is proportional to displacement and directed back towards the centre. The definition Leaving Cert Physics students state incompletely.
How to understand the photoelectric effect and work function
Below the threshold frequency nothing happens, no matter how bright the light. The photoelectric effect as Leaving Cert Physics examines it.
Why Most Students Struggle With Significant Figures
Your answer cannot be more precise than your least precise measurement. Significant figures in Leaving Cert Physics calculations and experiments.
The biggest misconceptions about friction in mechanics
Friction does not always oppose motion, and it is not always the same size. The friction misconceptions that cost Leaving Cert Physics marks.
The biggest misconceptions about static and kinetic friction
Static friction varies up to a maximum, kinetic friction does not. Why that difference decides which equation you should be using.
The easiest way to grasp half-life and radioactive decay calculations
Half-life questions are repeated halving, not a formula to memorise. Radioactivity calculations for Leaving Cert Physics.
The most common mistakes in applying the conservation of momentum
Momentum has direction, and ignoring the sign is where most marks go. Conservation of momentum in Leaving Cert Physics.
The most common mistakes in Kinematics calculations
Picking the wrong equation of motion, or the wrong sign for acceleration. Kinematics errors in Leaving Cert Physics and how to avoid them.
The most common mistakes when dealing with vectors and scalars
Adding speeds when you should be adding velocities. Where the vector and scalar distinction actually changes your answer.
The most frequent errors in calculating resistance in parallel circuits
The reciprocal step is the one students forget. Parallel resistance calculations in Leaving Cert Physics, and the check that catches errors.
The truth about centripetal force and circular motion mistakes
Centripetal force is not a new force, it is whichever force happens to point to the centre. Circular motion for Leaving Cert Physics.
The truth about magnetic flux and Faradays Law misconceptions
An emf is induced by changing flux, not by flux itself. Faraday and Lenz in Leaving Cert Physics, and the errors they catch.
Understanding the real difference between mass and weight
Mass is in kilograms and does not change, weight is a force in newtons and does. The distinction Leaving Cert Physics marks you on.
Understanding the real difference between transverse and longitudinal waves
Particles vibrate across the direction of travel, or along it. Telling wave types apart in Leaving Cert Physics, with the right examples.
Why Bohrs model of the atom is frequently misunderstood
Electrons occupy fixed energy levels, and light is emitted when they drop between them. The Bohr model as Leaving Cert Physics uses it.
Why Doppler effect calculations cause so many exam errors
Whether the source approaches or recedes decides the sign, and the sign decides the mark. Doppler calculations in Leaving Cert Physics.
Why projectile motion feels impossible and how to solve it
Horizontal and vertical motion are independent, and treating them separately makes projectiles routine. Leaving Cert Physics projectile problems.
Why students constantly mix up work energy and power
Work is energy transferred, power is the rate of transfer. Three related quantities, three different units, and where students merge them.
Why students fail to understand total internal reflection
Total internal reflection needs a dense to less dense boundary and an angle past the critical angle. Both conditions, not just one.
Why students get Kirchhoffs voltage and current laws wrong
One law is about junctions, the other about loops. Applying Kirchhoff correctly in Leaving Cert Physics circuit questions.
Why students struggle with Newtons Laws of Motion
The third law pair acts on two different bodies, which is the part almost everyone gets wrong. Newton laws of motion for Leaving Cert Physics.
Why understanding electric potential vs electric potential energy is difficult
One is measured per unit charge and the other is not. Separating electric potential from potential energy in Leaving Cert Physics.