Mod 4 Exam Qs Flashcards
An oscilloscope is connected to a microphone. The oscilloscope is used to determine the frequency of soundwaves omitted from a loudspeaker, describe how the trace on the silos scope screen can be used to determine the frequency of the sound waves.
Time period is calculated by counting the number of divisions that one full wave takes up on the display you then multiply this by the timebase
Frequency equals one divided by time period
A large, gap slit is placed in between a microwave, transmitter and a receiver. However, the receiver does not detect any microwaves when this gap was reduced the receiver now detect the microwaves. Explain why.
Most diffraction occurs when the gap is of similar size to the wavelength, therefore making the gap smaller will result in more diffraction so more waves can reach the receiver
The intensity of light incident on a light dependent resistor is increased the resistance decreases. What is the reason for this behaviour.
The number density of the charge carriers increases
The waves admitted from two sources are coherent, which quantity must be constant
Phase difference
Copper is a metal carbon is a semiconductor and ceramic is an insulator describe the difference between these materials in terms of the number. Density of free electrons include an explanation of the term number density.
Number density is the number of free charge carriers per unit volume
Therefore, a higher number 10 density result in better conduction
Copper has the greatest number density ceramic has the least number density,
Explain the variation of resistance with potential difference in a filament blank in terms of particles
As potential difference increases, current also increases, resulting in electrons flowing through the filament at a greater rate. These collide with the metallic ions and transfer energy to them, causing them to vibrate more. This result in electrons colliding with ions more frequently.
What direction is conventional current?
Anticlockwise
What is the difference between EMF and voltage?
EMF is energy from chemical energy store to electrical energy store PD is energy from electrical to heat
Is the work done on charges?
PD is the work done by charges
Stat Kirchhoff of second law and the quantity that is conserved
The sum of EMF equal the sum of potential difference in a closed loop
The quantity that is conserved is energy
A student conducts an experiment using two identical filament lamps and a variable power supply of negligible internal resistance
The lump are connected in series and the current in the circuit is 0.3 A
The EMF of the power supply is doubled and experiment is repeated the student expected the current also double but it doesn’t it is 0.4 A. Explain why
Lamps are non-omit conductors
Resistance of each lamp increases with current because of the increase of temperature
Describe how you can demonstrate in the lab reflected light is plain polarised
Using a polarising filter and rotating it so that the intensity will change
Define phase difference
The difference between two points on the same wave or points on two waves in degrees
What what is meant by interference?
The superposition of coherent waves
Loudspeaker admit soundwaves of frequency 2.8 Hz explain how you can use an oscilloscope to set a time base of 0.1 per division to check that the frequency of sound is 2.8
Play some microphone Close to the loudspeaker and connect it to an oscilloscope measure the number of divisions between adjacent peaks of the signal and the separation should be 3.6 divisions
Explain how we improve the fraction using a loudspeaker in a laboratory
Point a loudspeaker towards a slit the wood and compare the wavelength of the sound waves and the length of the split
