Summer Revision 2020 Past Paper Flashcards
What is the potential difference and frequency of mains electricity in the UK?
230 V and 50 Hertz.
What are the functions of an earth wire?
A safety wire to stop the case from becoming live.
What are the functions of the live wire?
Carries the current.
What are the functions of a neutral wire?
Completes the circuit.
Why should a person not touch an unconnected metal case?
They person could get an electric shock because there is a current in the person.
Why can a person touch a connected metal case?
The charge flows through the earth wire instead of the person,
because the resistance of the earth wire is much less than a person’s.
What happens if you touch a live wire?
Will cause a large potential difference across the body. A current will flow through the body.
For a thermistor, as temperature increases, resistance ___________.
decreases
What happens to sub-atomic particles in the nucleus in alpha decay?
The nucleus emits two protons and two neutrons.
What happens to sub-atomic particles in beta decay?
A proton is gained, but emits an electron.
What happens in gamma decay?
Both mass and atomic number do not change at all.
What are the differences in penetration for alpha, beta and gamma radiation?
Alpha radiation is the least penetrating. It can be stopped by a sheet of paper.
Beta radiation has a stronger penetration, but can be stopped by a thin aluminium sheet.
Gamma radiation is the most penetrating, it can only be stopped by thick lead.
Which type of radiation is the least ionising?
Gamma rays.
What is a gamma ray?
A gamma ray is when the nucleus tries to cool down, it will emit an electromagnetic wave.
Why did the student adjust the variable resistor every time the length of wire changed?
Because the variable resistor changes the resistance of the circuit.
So the current doesn’t change, so the temperature of the wire is constant.
What is the relationship between the length and resistance of a wire?
Directly proportional.
What is the equation for current?
And what is the unit for current?
current= potential difference/ resistance
Current is measured in Amps.
How does heat change different energy stores as water is heated?
Wood-
Pipe-
Water-
Wood- Chemical energy decreases.
Pipe- Thermal energy increases.
Water- Thermal energy increases.
Why does the temperature of water stay constant while burning? (2)
The heat energy is used to change the state of water from a liquid to gaseous water vapour.
The energy is also dissipated to surroundings.
Why is the thermal conductivity of metal important for bowl design?
Metal has a high thermal conductivity, so it increases the rate of energy transfer from the mixture towards the coolant.
Why is the thermal conductivity of plastic important for bowl design?
Plastic has a low thermal energy, so it slows down the rate of energy transfer from the outside to the coolant.
What is the definition of specific latent heat?
The amount of energy needed to change the state of 1kg of a substance without changing temperature.
Why are dice used to model radioactive decay and half-life?
Both are rolled at random processes.
Why can a kangaroo jump higher as their speed increases? (3)
Because the tendons stretch more,
increasing its elastic potential energy.
This is transferred to surroundings as gravitational potential energy.
