Chapter 9 - 12 Flashcards
Kirchhoff’s First Law
Sum of currents entering any junction are always equal to the sum of currents leaving.
Kirchhoff’s Second Law
Sum of the EMF in a circuit is equal to the p.d of the components.
Series circuit rules
Components connected in one loop.
Current same around whole circuit.
Total p.d is sum of components p.d
Parallel Circuit rules
Components connected in different loops
Current is added up at the top of circuit
P.d is same around circuit
Electromotive Force
When charges gain energy from power supply.
Work done on charge carriers
Potential Difference
Measure of electrical energy
Measures energy loss.
Ohms Law
For a metallic conductor kept at constant temperature, the current is directly proportional to the p.d across the ends.
When temperature of wire increases
Positive ions gains internal energy and vibrate more
Frequency of collisions increase, resistance increases
More energy transferred when travelling through wire,
3 factors affecting resistance
Material of wire
Length of Wire
Cross sectional area
Thermistor
Electrical component made from semi conductor with negative temperature co - efficient. As temperature increases, resistance decreases
Resistivity Equation
R = pL / A
Internal Resistance
When there is a current in the power source, energy is lost which is transferred to heat.
EMF = terminal p.d + lost volts`
Potential Divider Equation
V out = (R2/ R1 + R2) x V in
Longitudinal Wave
Direction of movement is parallel to transfer of energy direction.
Transverse Waves
Direction of movement is perpendicular to transfer of energy direction.
Give examples of transvers waves
EM waves
Seismic Waves
Waves of surface of water
Example of longitudinal wave
Sound Waves
P - Waves
Define Progressive Waves
An oscillation that travels through matter
They all transfer energy
Wave speed equation
frequency x wavelength
frequency equation
1 / time
Phase Difference
The difference between displacements of particles along a wave.
Reflection
When a wave changes direction at a boundary.
Refraction
When a wave changes direction as it changes speed, passing from one medium to another.
When wave slows down wavelength…..
decreases
Diffraction
When waves pass through a gap or obstacle the waves will spread out.
Speed, wavelength, frequency remains same.
Polarisation
When the particles oscillate in only one direction.
Confined to a single plane.
Partial Polarisation
When transverse waves reflect off a surface, they become partially polarised.
Which type of wave is already polarised
Longitudinal Wave
Intensity
The power passing through a surface per unit area.
I = P/A
What is intensity proportional to?
( Amplitude )^2
what is c equal to
3 x 10 ^ 8
Refractive Index equations ( 3 )
n = c / v
n = 1/sin c
n1 sin theta 1 = n2 sin theta2
Total Internal Reflection
When a light ray strikes a boundary at a larger angle to the normal, it will be totally internally reflected.
What are the two conditions for TIR
The light must be travelling through a medium with a higher refractive index as it hits the boundary
The angle at which it hits must be higher than the critical angle.
Principle of superposition of waves
When two or more waves cross at a point, the displacement at that point is equal to the sum of displacements of the individual waves.
Constructive interference
For two waves in phase, the maximum positive displacements add together.
Destructive Interference
For two waves in antiphase, the maximum and minimum of each wave form a smaller waves
Coherence
When waves emitted from two sources have a constant phase difference.
Must have same frequency
Path Difference
The distance a wave has travelled from its source to any point the wave.
Distance - m
Phase Difference
The difference between two waves when they pass the same point.
Degrees / Radians
Youngs double slit formula
lambda = ax / D D = distance from slit to screen x = width of light ray a = gap between the slits
Stationary Waves
Formed when two waves with the same frequency and amplitude traveling towards each other are superposed
Node
The two waves cross at the middle when displacement is equal to 0
Antinode
The waves meet at maximum displacement.
Energy transfer in progressive waves vs stationary waves
Progressive - Energy transferred in the direction of the waves
Stationary - No net energy transfer
Wavelength in progressive waves vs stationary waves
Progressive - Minimum distance between two adjacent points in phase
Stationary - Twice the distance of two adjacent nodes.
