Key Definitions Flashcards
Define EMF.
The amount of electrical energy produced by a battery/source per unit of charge.
Define Power.
The rate of transfer of electrical energy to a component per second.
Define Resistance.
Potential difference divided by the current, ie. the electrical energy used when a current of 1A moves through a component.
Define Potential Difference.
The amount of electrical energy converted or transferred per unit of charge between 2 points.
Define Ohm’s law.
The current passing through a conductor is proportional to the voltage as long as the physical conditions remain constant.
Define Resistivity.
Resistance in Ohms multiplied by the cross-sectional area in metres squared divided by the length of the object in m.
Define Critical/Transition Temperature.
The temperature that below which a superconductor has no resistance, so large currents can pass through it with no energy loss.
Define Internal Resistance.
An electrical source or cell’s opposition to the flow of charge through it, defined as the loss of pd per unit current when a current passes through the source/cell.
Define Isotope.
Nuclides with the same number of protons but different numbers of neutrons.
Define Pair Production.
When a particle and its corresponding antiparticle are produced from a photon with energy greater than the total rest energy of the 2 particles.
Define Annihilation.
When a particle and its corresponding anti-particle collide, converting all of their energy and mass into 2 high energy photons.
Define Moment.
Force multiplied by perpendicular distance between the pivot point and the line of action of the force.
Define Principle of Moments
States that for an object to be in equilibrium, the sum of the anticlockwise moments = the sum of the clockwise moments.
When is an object in equilibrium?
When the sum of anticlockwise moments = sum of clockwise moments and all vertical forces cancel and all horizontal forces cancel.
Define Couple.
A pair of equal and opposite forces separated by distance, d, acting about point, p: the turning effect at point p is equal to one of the forces multiplied by the perpendicular distance between the forces.
Define Centre of Mass.
Where all of an object’s mass appears to act about and moments cancel.
Define Newton.
Force required to accelerate 1kg by 1ms^-2
Define the Law of Conservation of Energy
Energy is never created or destroyed, just transferred between different types.
Define Hooke’s Law.
The extension of a spring is proportional to the force applied to it as long as the limit of proportionality is not exceeded.
Define Stress.
Force per unit area.
Define Strain.
Ratio of extension to original length.
Define Young’s Modulus
Tensile stress divided by tensile strain; the stiffness constant of a material.
Define Longitudinal Wave.
A propagating wave with oscillations in the same direction of propagation/energy transfer.
Define Transverse Wave.
A propagating wave with oscillations perpendicular to the direction of propagation.
Define Stationary Wave.
Formed when 2 waves of similar frequency travelling in opposite direction interfere and the resultant wave is the vector sum of each wave’s displacements at that point by the principle of superposition.
Define Diffraction.
Spreading out of a wave when passed through a slit or around an obstacle.
Define Coherent.
Same frequency and constant phase difference.
Define Constructive Interference.
2 waves intersect and interfere through the principle of superposition and the resultant displacement is the vector sum of the 2 waves’ displacement at the point.
What is the difference between single and double slit diffraction?
Single slit: Wide central maxima 2x width of others, and reduction in intensity going away; Double slit: Same width, going out.
