Final Notes

Question 1

Momentum equation?

Answer 1

Momentum (kgm/s) = mass x velocity

Question 2

Equation for force acting?

Answer 2

Force acting (N) = momentum / time taken for change to happen

Question 3

Polythene rod with duster?

Answer 3

Electrons move from duster to rod

Question 4

Acetate rod?

Answer 4

Electrons move from rod to duster

Question 5

What happens as charge builds up?

Answer 5

So does voltage, causing sparks

Question 6

How does lightning occur?

Answer 6

Rain drops collide knocking off electrons

Top of cloud becomes positive, bottom is negative

Creates big voltage and spark

Question 7

Fuel filling problem?

Answer 7

As fuel flows out of pipe static increases (friction)

This can lead to spark and explosion

Nozzles made of metal to conduct charge away

Earth straps do the same

Question 8

Equation for wavespeed?

Answer 8

Wavespeed = wavelength x frequency0

Question 9

Equation for frequency?

Answer 9

Frequency= 1 / time period (time for one complete wave to pass)

Question 10

What increases diffraction?

Answer 10

Shorter the gap, and longer the wavelength

Question 11

How to find refractive index?

Answer 11

n = sin I/ Sin r

Question 12

How to find critical angle?

Answer 12

Sin c = 1/N

Question 13

Analogue signals?

Answer 13

Can take any value in a certain range

Amplitude and frequency vary

Question 14

Digital signals?

Answer 14

Only takes 2 values, on/off

Question 15

Advantages of digital?

Answer 15

Doesn’t lose quality when amplified

Isn’t affected by interference

They can be compressed without losing a lot of information

Question 16

Conduction?

Answer 16

Process where neighbouring particles pass on their extra kinetic energy by vibrating

Question 17

Convection?

Answer 17

Water heated

Particles get more energy, move faster

So it expands and becomes less dense

Rises above cooler water forcing it down to heat

Cycle continues in the convection current

Question 18

Equation for work done?

Answer 18

Work done= force x distance moved

Question 19

Equation for power?

Answer 19

Power= work done / time taken

Question 20

Evaporation?

Answer 20

Particles can evaporate bellow boiling point if, travelling in right direction , and have enough kinetic energy to break forces of attration between other particles

Causes liquid to cool as average kinetic energy decreases

Question 21

Pressure and volume equation?

Answer 21

Pressure x volume = constant

Question 22

Pressure and temp equation?

Answer 22

Pressure / temp in k = constant

Question 23

Motor effect?

Answer 23

Current passes through wire

Induces magnetic field in wire

This interacts with permanent magnetic field

Puts force on the wire

Determined by LHR

In loudspeakers, vibrations from force make sound

Question 24

Step up transformers?

Answer 24

Increase voltage

More coils on secondary

Question 25

Step down transformers?

Answer 25

Decreases voltage

Less coils on secondary

Question 26

Formula for voltatge and coils?

Answer 26

Input voltage/ output voltage = number of turns on primary/ number of turns of secondary

Question 27

Formula in transformers involving power?

Answer 27

Voltage1 x current 1 = voltage 2 x current 2

Question 28

How a transformer works?

Answer 28

Steps down, or steps up voltage

Current in primary coil produces a magnetic field

The current alteranates

Causing a change in the magnetic field of the soft iron core, as it magnetises and demagnetises quickly

This field interacts with the secondary coil

Inducing a voltage in the secondary coil

Transformers don’t work with DC

Question 29

How to answer 4 mark describe question?

Answer 29

Name instruments to measure all variables

How independent variable will be varied

Obtain a range of results

Take repeats

Draw graph