Physics OCR B & A level Package

Define Young’s Modulus. The Young’s Modulus of a material its ratio of tensile stress to tensile strain. It is a measure of a material’s stiffness. How is stress calculated? Stress = Force/Cross-Sectional Area How is strain calculated? Strain = Change in Length/Original Length What is ...

Why are X-rays used in medical imaging often referred to as ‘soft X-rays’? Because they have energies that are lower than gamma rays. How are X-rays produced? By rapidly accelerating or decelerating charged particles – their kinetic energy is transferred into highenergy photons How can yo...

Define Magnetic Field. A region of space in which moving charged particles are subject to a magnetic force. This force is caused by the interaction of two Magnetic Fields (there is a field around the moving charged particles which interacts with the existing Magnetic Field they are passing throu...

Absolute Temperature A temperature value relative to absolute zero. Absolute Zero The lowest possible temperature of a system, where no heat remains and the particles in the system have no kinetic energy. Avogadro Constant The number of particles that make up one mole of any gas. Boltzmann C...

How does the alpha-scattering experiment give evidence of a small, dense nucleus? A few alpha particles bounce back. This wouldn’t happen if the positive charge in the atom was distributed evenly throughout (as in the Plum Pudding Model), which suggests they must be hitting a dense positive ch...

1. Define the term ‘progressive wave’. A wave that transfers energy from one place to another with a wave front which travels through the material (in contrast to stationary waves which don’t appear to move). 2. What is a longitudinal wave? Waves which the particles oscillate in the sam...

Absolute Uncertainty The interval that a value is said to lie within, with a given level of confidence. Accuracy A measure of how close a measurement is to the true value. Analogue Apparatus Measuring apparatus such as rulers, beakers and thermometers that rely on the experimenter reading off...

What is an uncertainty? An uncertainty in a measurement is anything that may cause the value to differ from the true value. What is the resolution of a measuring instrument? The resolution of an instrument is the smallest increment that produces a noticeable change in the value. How do you com...

How can you calculate the total resistance of a combination of resistors in series? The total resistance equals the sum of the individual resistances. R = R₁ + R₂...+ Rₙ How can you calculate the total resistance of a parallel combination of resistors? The total resistance equals the inver...

What is a source’s internal resistance? A source’s internal resistance is the resistance of the materials inside the source. It is equal to the lost volts per unit current in the source. What is the emf of a power source? A power supply’s emf is the work done by the source per unit charge...