Questions Corrections 2021 Flashcards
What does direct potential difference mean
The polarity of the supply does not change (p.d in one direction only)
Suggest why models of nuclear fission power stations were tested before building the first commercial power station
To assess safety risks
To assess efficiency of the process
Describe a method student A could use in his investigation of how the current in resistor R at a constant temperature varied with the potential difference across the resistor
The student recorded both positive and negative values of current
1) Measure the current in R using an ammeter and ensure current is low to avoid temperature increase
2)Measure the potential difference across R using the voltmeter
3)Vary resistance of the variable resistor
4)Record a a range of values of current and p.d
5) Switch circuit off between readings
6) Reverse connection of R to power supply and repeat measurements of IV in negative direction
7) Plot a graph so current against p.d
Give two reasons why it’s better to use a digital ammeter rather than a moving coil ammeter
Less chance of misreading
Higher resolution
The student only measured the volume of fruit once, why can’t the volume measurements be used to show that the method to measure volume gives precise readings
Repeat readings of volume need taking to show the readings are close together
What is the conversion of kW to W
1kW = 1000W
Why is it unlikely that all of the electricity that the UK needs can be generated by solar power systems
A really large area of land would need to be covered with solar cells
As number of hours of daylight is too low
What is meant by the random nature of radioactive decay
Can’t predict when a particular nucleus will decay
Conversion of mW to W
Divide by 1000
1mW= 0.001
Explain how closing the switch would affect the current in the variable resistor
Current would be almost zero in the variable resistor
As the switch has effectively zero resistance
When the volume of gas in the syringe increased the pressure on the inside of the walls of the syringe decreased
Explain why
There are less frequent collisions between the particles and the walls of the syringe
Causing a lower force on the walls of the syringe
And pressure us the total force per unit area
Explain the advantage of transmitting electricity at a very high potential difference
A very high p.d means very low currents
Which means less energy is transferred to surroundings
Which increases efficiency of power transmission
A person could receive a fatal electric shock when flying a kite if the kite was very close to but not touching the power cable, explain why
Electric field strength is very high
Causing air to become ionised
The kite conducts charge to the person
Explain why the current in the steel wire is different to the current in a single aluminium wire
The potential difference across the wires is the same
But the resistance of the steel wire is greater
Conversion kJ to J
1kJ is 1000J
