Advanced Notice Article

Question 1

Time period

Answer 1

The time taken for a wave to complete one full cycle/oscillation

Question 2

Frequency

Answer 2

The number of wave cycles that occur each second/the number of points on a wave that are in phase that pass a point per second

Question 3

Link T and f

Answer 3

T = 1/f

Question 4

Wave equation

Answer 4

v = f (lamda)

Question 5

Inertia

Answer 5

Resistance to change in motion - electrons have this due to low mass (so can be moved quickly by an electric field)

Question 6

Minimum sampling frequency

Answer 6

2xmax frequency

Question 7

Bandwidth

Answer 7

Approximately equal to data rate (bits per sample/sample per second)

Question 8

Quantisation error

Answer 8

The difference between analogue and digital signals. Given by 1/2^no. bits per sample

Question 9

Why are lead-acid batteries bad

Answer 9

They are very heavy, and therefore limit top speed of cars

Question 10

Are electric cars ‘green’

Answer 10

Depends. If they are recharged from an electrical supply generated from renewable resources, yes!

Question 11

Problems with electric cars

Answer 11

Take time to charge, and a lack of a charging network. Expensive, if drive at full speed will run down battery quickly

Question 12

How to carry out pendulum experiment

Answer 12

Vary length of l and record effect of T. Keep amplitude (theta) constant. Plot T^2 (y) against l (x), gradient is 4pi^2/g.

Question 13

How to find suitable value for amplitude, theta

Answer 13

Keep l constant and vary theta to find a value which isn’t too big that it will result in the equation not working, but isn’t too small that theta is immeasurable.

Question 14

Systematic uncertainties in pendulum experiment

Answer 14

Not measuring l to centre of mass

Question 15

Random uncertainties in pendulum experiment

Answer 15

• In T (stopwatch and reaction time)

- In l

Question 16

Minimising uncertainties in pendulum experiment

Answer 16

• Plot graph to remove systematic error (BUT if systematic error in T, will effect T^2 differently, so will effect the gradient)
• Do many replicates (at least 3)
• Measure size of bob with micrometer so don’t have to measure to centre each time
• Measure T over multiple oscillations, reducing % uncertainty
• Feducial line to help mark start/end of an oscillation

Question 17

Advantages of graphical methods of calculation

Answer 17

• Removes systematic error

- Reveals overall effect of uncertainties through scatter of points

Question 18

What happens with a stretchy string

Answer 18

-Measurement of l will be too small, so g will be small

Question 19

What happens with a larger mass

Answer 19

-No change

Question 20

What can be displayed on a CRO?

Answer 20

Only repeating signals

Question 21

What is self-discharge?

Answer 21

When a battery loses its capacity to hold charges: can’t hold ‘max amount’. Storage in low temperatures can reduce this

Question 22

Wh

Answer 22

A unit of ENERGY.

Question 23

Lead-acid; NiMH and lithium-ion battery discharge

Answer 23

4-6%, 30%, 2-3% per month

Question 24

2 ways of measuring uncertainties (not graphically)

Answer 24

• average uncertainty: add all PERCENTAGE uncertainties together (if squared, double)
• maximum uncertainty: calculate max and min value for g, biggest difference between max/min and actual is absolute uncertainty

Question 25

Cathode

Answer 25

A piece of wire with a p.d. across it and a current. Heats up, and electrons leave

Question 26

How do CRO’s work?

Answer 26

Electrons leave cathode and accelerate to the anode, gaining kinetic energy, which can be equated to electrical energy (eV = 0.5*mv^2)
X + Y plates move the beam. X plates are charged and sweep the beam across the screen; Y plates give vertical deflection (varying p.d.)