physics mock mistakes

Question 1

how does the speed of gamma rays in a vacuum compare with the speed of light waves in a vacuum?

Answer 1

gamma rays travel at the same speed than light waves

Question 2

what is meant by a renewable energy resource

Answer 2

a renewable energy resource is one that is being replenished as its used- it will not run out

Question 3

explain one advantage of using biofuel rather than diesel made from crude oil

Answer 3

• renewable fuel
• does not increase level of carhbon dioxide in the atmosphere so it does not contribute to global warming

Question 4

descibe the spring extension practical

Question 5

describe one use of a thermistor

Answer 5

-used in a thermostat to switch a device on/off at a specific temperature

Question 6

explain hoe the potential difference across a resistor would change as the temperature of the thermistor increased

Answer 6

the total resistance of the circuit decreases, current in the circuit decreses, the resistance of resistor is constant
- v+ir therefore potential difference increases OR temperature increases, the resistance of the thermistor increases, potential difference shared between components, potential difference across the thermistor decreases therefore potential difference across the resistor increases.

Question 7

explain how the crash barrier helps prevent injuries to the passengers on the train

Answer 7

the foam compresses so the time taken for the train to stop increases compared to hitting the wall, therefore rate of change of momentum decreases therefore reduces force on passengers

Question 8

give two advantages of using a switch mode transformer rather than a basic transformer in a mobile phone charger

Answer 8

-its lighter, smaller and portable

-very little power used when load applied

Question 9

an alternating potential differece across the coil in the wirless charging pad creates an alternating current in the coil inside the mobile phone

Answer 9

there is a alternating current in the coil in the charging pad which causes an alternating magnetic field across the coil in the mobile phone which induces a alternating potential difference across the coil in the mobile phone which creates an alternating current

Question 10

why are circuit breakers better than fuses

Answer 10

• circuit breakers can reset
  circuit breakers can operate much faster

Question 11

which wire should be coonected to the metal case to protect the user of the appliance

Answer 11

earth wire

Question 12

describe two differences and two similarities between the properties of sound waves and electromagnetic waves

Answer 12

differences:
- sound is a longitudinal wave, electromagnetic waves are transverse waves
-electromagnetic waves can travel through a vacuum and sound waves need a medium to travel through

similarities:
- both transfer energy/info
- both can be diffracted
both can be refracted
both can be reflected

Question 13

explain hoe the eye changes to allow light from a distance object to fucos on the retina

Answer 13

cilliary muscles relax
makes lens thinner
so focal length increases

Question 14

describe motor effect

Answer 14

a conductor is in a magnetic field
a current in a conductor produces a magnetic field
so there is a force on the conductor

Question 15

explain one advantage of a computer fan that has adjustable speed

Answer 15

• the fan can run more slowly- when less coooling is required
  so
• less power/energy transferred
  -quiter
  -lasts longer