Physics things i forgot

What is meant by ‘direct potential difference’

The polarity of the potential difference doesn’t change

Equation linking energy, charge flow and potential difference

E = QV

What is meant by ‘direct potential difference’

The polarity of the potential difference doesn’t change

Equation linking energy, charge flow and potential difference

E = QV

Would a shorter or longer half life cause more damage?

shortest half-life = most intense radiation in the short term = greater immediate danger, since the body has less time to repair the damage

Define ohmic and non-ohmic conductors, include I-V graph shapes and conditions

• Ohmic conductor: Current is directly proportional to voltage at constant temperature.
  

  • Graph: Straight line through origin

  • Example: Resistor, metal wire

• Non-Ohmic conductor: Current and voltage are not proportional.
  

  • Resistance changes as current changes.

  • Graph: Curved or asymmetrical

  • Examples: Filament bulb, diode, thermistor

Explain why the filament bulb is a non-Ohmic conductor, using a particle-level explanation and an I-V graph.

• As current increases, filament heats up

• Higher temperature = metal ions vibrate more, making it harder for electrons to pass

• So resistance increases

• Graph: Curved, flattens at high voltage (current increases slower)

Describe how current flows in a diode, thermistor, and LDR. Include real-world uses.

• Diode: Allows current in one direction only; blocks reverse.
  

  • Needs threshold voltage to conduct

  • Used in rectifiers (AC → DC)

• Thermistor: Hotter = lower resistance
  

  • Useful in temperature sensors, e.g., thermostats

• LDR: Brighter = lower resistance
  

  • Used in automatic lights (e.g., street lamps)

Describe a method to investigate how the current in a filament lamp varies with the potential difference across the filament lamp

GET FROM CHATGPT

List the sub-atomic particles in order of discovery

electron - J.J Thompson

nucleus - Rutherford

proton - Rutherford

neutron - James Chadwick

Explain why the air pressure in a car tyre changes if the temperature of the air in the tyre increases

-as temperature increases particles have greater (mean) kinetic energy

-so more frequent collisions

-and greater force in each collision

greater force per square metre causes greater pressure (on wall of tyre)

State two ways to reduce unwanted energy transfers

-lubrication - reduces friction
-thermal insulation - reduces energy lost by convection

Give ways that energy can be lost (wasted) to the surroundings

-heat
-light
(sound)

Describe how fuel power stations work to produce electricity

-fossil fuel (mainly coal) is combusted to release heat
-the heat evaporates water into steam
-the steam convects through the boiler, turning the turbines
-the turbines spin the generator, which produce electricity
-electricity is conducted across the land

Give environmental advantages of using a wood burning stove

-wood is carbon neutral
-wood is renewable
-wood would conserve fossil fuels

Explain, in terms of particles, how heat is transferred through the glass wall of a boiling tube(or through any material)

-particles vibrate with more kinetic energy/faster
-energy is transferred by collisions with other particles
-heat moves from higher to lower temperatures (through conduction)

Give advantages of using a datalogger instead of a thermometer

-greater sensitivity/precision (DO NOT SAY MORE RELIABLE)
-could link to a computer for data analysis
-could take more frequent readings
not affected by parallax error

How does the temperature of an object increase

-if it absorbs more energy than it emits

Describe how to determine the specific heat capacity of a material (required practical)

-measure mass of material being tested
-measure initial temperature of material using a thermometer/datalogger

-switch on heater
-record energy input using a joulemeter (or connecting an ammeter and voltmeter, multiplying current and voltage, then multiplying that by the time taken)
-record final temperature, find temp change
-plot graph of energy (X) against temp (Y)
-use the gradient or equation to find the SHC

-insulate the beaker of water, eliminate air gaps using Vaseline, add a lid