Revision

Question 1

From what point does weight act

Answer 1

Centre of gravity

Question 2

Why are beta particles used for thickness

Answer 2

• alpha particles would not penetrate through and are absorbed
• gamma particles are too penetrating so are not absorbed
• some beta particles are absorbed but some can penetrate through, so the thinner the aluminium, the more beta particles go through

Question 3

Charges of an alpha particle and beta particle

Answer 3

Alpha particle : +2

Beta particle: -1

Question 4

What is meant by a digital signal

Answer 4

A signal that only has two values, 0 and 1

Question 5

Ways that a digital signal could be made to carry more information

Answer 5

• use an additional signal level
• use multiplexing )more than one channel)
• increase the frequency of the wave

Question 6

What happens when a storm cloud discharges

Answer 6

• electrons move to the bottom of clouds

- These are then discharged to earth through lightning

Question 7

How a warm charger affects the output of it (transformer)

Answer 7

• Energy is lost
• The efficiency is no longer 100%
• The resistance of it will increase with temperature

Question 8

Why do you alpha particles and beta particles have different penetrating powers

Answer 8

• alpha particles have less penetrating power
• alphas have more charge
• Alphas cause more ionisation
• alphas have more mass
• alpha particles are more likely to collide with atoms as they’re larger
• slowing force on alpha particles is larger

Question 9

Graph to show resistance

Answer 9

• voltage (Y-axis)
• current (x-axis)

Gradient is resistance

Question 10

Experiment with an oscilloscope

Answer 10

• Attach the microphone to the oscilloscope, ensuring the CRO and the microphone are turned on
• strike the tuning fork and hold it near the microphone
• adjust time division section so that one complete cycle is shown on the CRO screen
• read off the period
• use the formula frequency = 1/time period to calculate the frequency of the soundwave

Question 11

Why is electrical energy transmitted using very high voltages

Answer 11

• high-voltage leads to low current
• P=IV
• less energy is lost from the wires (resistance/ heat loss)
• more efficient

Question 12

Explain the meaning of ‘50 Hz alternating current’

Answer 12

• 50 cps (cycles per second)
• current that changes direction continuously (switches from positive to negative)

Also: direction changes 100 times per second

Question 13

Why must DC from the generator be changed to AC before it is transmitted

Answer 13

• because transformers change the current

- Transformers only use alternating-current

Question 14

Half life definition

Answer 14

Time taken for radioactivity to half

Question 15

Why do lighter objects reach the ground slower

Answer 15

• lighter objects reach terminal velocity sooner than heavy objects
• because a smaller drag force is needed
• so average velocity of lighter object is lower
• so it falls slower and reaches the ground after the larger object