physics (triple content) year 9

method to the experiment investigating how insulating materials can be charged by friction

1. rub a polythene (opaque) rod and a duster and then place it on the coulomb meter

2. polythene becomes negatively charged

3. repeat with an acetate (transparent) rod

4. acetate becomes positively charged

5. balance a rod on a watch glass and bring the other rod towards it

6. watch to see if the balanced rod is repelled by or attracted towards the second rod

what is the conclusion to the experiment investigating how insulating materials can be charged by friction

opposite charges attract = polythene + acetate

like charges repel = acetate + acetate = polythene + polythene

what electrostatic charge is produced by the loss of electrons

positive electrostatic charge

what electrostatic charge is produced by the gain of electrons

negative electrostatic charge

in the experiment investigating how insulating materials can be charged by friction what charge does the polythene rod have and why

negative electrostatic charge due to it gaining electrons

in the experiment investigating how insulating materials can be charged by friction what charge does the acetate rod have and why

positive electrostatic charge due to it losing electrons

what can you use the experiment with the polythene rod and the duster for when giving an example of an electrostatic phenomena = balloon + wall

1. when rubbing a balloon the balloon gains electrons meaning has a negative electrostatic charge

2. the wall is neutral so the negative charges in the wall are repelling the balloons negative charge

3. leaving a net positive charge on the walls surface which is nearest to the balloon

4. as opposites attract the negatively charged balloon is attracted to the positively charged wall causing it to stick

how do photocopiers use electrostatic charges

1. they use static electricity to copy paper documents

2. an image of the document gets projected onto a positively charged copying plate

3. the plate loses its charge in the light areas and keeps positive in dark areas

4. the negatively charged ink is applied to the plate and sticks to the positively charged parts

5. it then gets transferred onto the piece of paper

what are the potential dangers of electrostatic charges when fuelling aircrafts

1. a build up of static charge can happen when fuelling planes could become a potential danger

2. fuel runs through the pipes very fast and is very flammable

3. the friction between the fuel and the pipe causes the fuel to gain charge

4. if this charge were to cause a spark it could leak to the fuel catching alight and cause an explosion

how ton prevent the potential dangers of electrostatic charges when fuelling aircrafts

1. this is prevented by the fuel tank being connected to the earth with a copper wire called the bonding line = when refuelling

2. the conductor earths the plane by carrying the charge through the earth and removing the risk of sparks

3. this is because it is easier for the charge to flow down the bonding line than to spark

what is the frequency range for human hearing

20 - 20000 Hz

what is the method to investigating the speed of sound in air

1. measure the distance of where you are standing to the wall = the distance should be atleast 50m so the sound has to travel 100m allowing the time to be large enough to be measured

2. then double this distance = due to the sound travelling there and back

3. start the stop clock when you make a noise

4. the stop the clock when you hear the noise you just made

5. repeat this 3 times and find the average

6. find the speed using speed = distance/time

how can an oscilloscope and microphone be used to display a sound wave

1. the microphone is plugged into the oscilloscope and a sound is played through the microphone

2. the microphone transfers the sound into an electrical signal which the oscilloscope can display

3. the x axis on the graph shows the time base which can be adjusted so time period and frequency can be calculated

4. the y axis on the graph displays voltage as the wave is converted into an electrical singal meaning amplitudes can be compared

what does a high frequency of vibrations from the source mean for the pitch + why

it means a high pitch = as the object vibrates with a high frequency it causes the sounds to be higher

what does a high loudness of a sound mean for the amplitude of the source + why

it means a greater amplitude = as bigger vibrations mean more energy is being put in so more energy out in sound