Paper 1 Flashcards
Explain why connecting the Earth wire to a metal case of a plug is Safe
Because if the live wire touches the metal case then the current will flow through the Earth wire rather than the human touching the case because the Earth wire has a lower resistance on the human
Hey student investigated how the resistance of a piece of wire varies with length in a circuit with a variable resistance explain why the student needed to adjust a variable resistor each time she change the length of the wire
A variable resistor changes the resistance of the circuit so it keeps the current the same for each length of wire so that the temperature of the wire is constant
Why does 1 kg of a gas have much larger volume down 1 kg of a solid
Particles in a solid have strong forces of attraction which allows them to have a fit structure however particles in a gas have negligible forces therefore the particles are far apart and they are more likely to take up more space
Explain why the total positive charge in an atom of an element is always the same
Protons gives the nucleus a positive charge and the number of protons of every atom of the same element is the same
Explain how a cavity wall reduces unwanted energy transfers
Cavity wall has two or more layers therefore it has a low thermal conductivity so the energy transferred by conduction is reduced
Explain the energy stores of a boiler that has a fuel cold water and a hot exhaust gas
Chemical energy store of the fuel reduces and energy transferred to the thermal energy store of the water and the air heating up the surroundings
Explain how a reading on a circuit of ammeters and voltmeters changes as environmental conditions change on a circuit containing an LDR
Resistance of the LDR changes when the light intensity changes. As light intensity Increases the resistance of the LDR decreases therefore the overall resistance in the circuit decreases.
This means that the current reading on the ammeter will increase as the overall current increases in the circuit. And the potential difference across the LDR will therefore decrease so the reading on the voltmeter will also decrease
How should a student change a circuit to give negative values for current and pd
Reverse the connections to the cell
The difference between direct and alternating potential difference
Direct potential difference is always in the same direction however alternating potential difference changes direction
Explain why it is better to use a cable with do you know resistance when connecting to a car
No resistance means high currents therefore the battery of the car charges faster
A student increases the temperature of a thermistor explain how the current in the thermostat changed
Current increased as resistance decreased
Switch closes in the circuit containing a lamp how will the potential difference across the lamp change after the switch is closed
Potential difference across the lamp will increase as the current will increase because the circuit is complete
Explain why the temperature heating element increases in a kettle when it is connected to the mains supply
Electrons collide with particles in the heating element which increases the thermal energy of the particles
Explain Y on a graph the time taken for kettle to switch off does not go through the origin
Because the castle took time to heat up
Why is it difficult to detect gamma radiation
Gamma radiation can pass through any detector
Explain why a count rate detecting the activity of a radioactive substance is less than its actual activity
Radiation spreads in all directions and only some of the radiation that passes through passes through the Geiger-Müller tube is detected
Explain when handling a radioactive substance a teacher stood as far away as possible
So they reduce irradiation from the radioactive source as it eradication increases risk of cancer
Why would it be safe person to touch a metal case when the live wire has touched the case
The current flow through the Earth wire as the resistance of the Earth wire is lower than the resistance of the person
The temperature of water stays constant even though it is continued to be heated why
Energy is dissipated to the surroundings at the same rate that energy is transferred to the water therefore it cannot increase in temperature
What is the motion of the particles in solid ice cream
They vibrate about in fixed positions
When a liquid is called and frozen what happens to the kinetic and potential energy of the particles
Both decrease
Explain the property a liquid coolant should have
A high specific heat capacity so it can absorb more energy with only a small temperature decrease
ANB are both radioactive sources source a has a longer half life than B what does this mean
The nuclei in source A are more stabler
Explain why a kangaroo can jump higher as speed increases
Because the max extension increases therefore elastic potential energy also increases this is transferred to the gravitational potential energy
