In our last post, we talk about some common O-Level Physics mistakes (Part 1). This week, we’re diving into Part 2.
Pressure in Fluids
Common Misconception: Students sometimes confuse pressure with force.
Pressure (P): Defined as the force per unit area, given by the formula P = F/A
where F is the force applied and A is the area.
Tip: Remember that pressure depends on the area. A small force over a small area can produce high pressure.
Thermal Energy and Temperature
Common Misconception: Students may mix up temperature with thermal energy.
Temperature: Measures the average kinetic energy of particles in a substance.
Thermal Energy (Internal Energy): The total energy (both kinetic and potential) of all particles in a substance.
Tip: Thermal energy is also known as Internal Store. Thermal Energy/Internal Energy Store: This energy represents the energy due to the motion (kinetic) and position (potential) of particles within an object or substance.
Reflection and Refraction of Light
Common Misconception: Students often confuse the laws of reflection and refraction.
Law of Reflection: The angle of incidence equals the angle of reflection.
Law of Refraction (Snell’s Law):
n₁ sin(θ₁) = n₂ sin(θ₂)
where n₁ and n₂ are refractive indices.
Tip: Angle of incidence is the ANGLE BETWEEN incident ray and the NORMAL. (Not angle between incident ray and plane). Angle of reflection/ refraction is the ANGLE BETWEEN reflected / refracted ray and the NORMAL not the plane.
Calculating Resultant Forces
Common Misconception: Students often make mistakes when calculating the resultant force, especially with forces in opposite directions.
Concept: The resultant force is the vector sum of all forces acting on an object. When forces act in opposite directions, they should be subtracted.
Tip: Always sketch a diagram to visualize the direction and magnitude of each force.
Common Misconception: Students sometimes forget to consider all forces acting on an object when applying Newton’s Second Law.
Concept: Newton’s Second Law states that the net force on an object is equal to its mass multiplied by its acceleration, or F = ma.
Tip: Break down the problem into smaller steps. First, identify all forces acting on the object, calculate the net force, and then apply the formula to find acceleration.
Magnetic Fields Around Current-Carrying Wires
Common Misconception: Students may struggle to visualize magnetic fields around current-carrying wires and describe their direction incorrectly.
Tip: Use the RIGHT-HAND GRIP RULE to determine the direction of magnetic field produced (Clockwise or Anti-clockwise) around a straight conductor OR the direction the magnetic field (THUMB direction is N-pole) for a coil wire.
Identifying Directions of Force, Magnetic Field, and Current in Electromagnetic Situations
Concept: Use your right hand for the Fleming’s Left-Hand Rule:
Thumb points in the direction of the force.
Index Finger points in the direction of the magnetic field.
Middle Finger points in the direction of the current.
This helps in determining the directions of force, magnetic field, and current in questions on electromagnetism.
Finished!
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