Physics Paper 1

Explain why solids are usually denser than liquids and gases

There are more particles in a certain volume as there is less space between them.

State the formula for density

Density = mass / volume. ρ = m / v. ρ - rho.

What is the unit for density determined by?

The mass and volume units.

How many g / cm³ is 1 kg / m³?

0.001

Describe a practical method to measure the density of an irregular object

Place the object on scale and measure the mass. Place a Eureka can next to a measuring cylinder so the spout can pour water into it without spills. Pour water into the Eureka can until it reaches above the spout. Pour away excess water in the measuring cylinder. Steadily lower the object into the Eureka can, and record the volume of water displaced into the measuring cylinder. Density = mass / volume.

Describe a practical method to measure the density of a liquid

Measure the mass of a measuring cylinder with a scale then pour in some liquid and measure the new mass. Find the difference and divide this by the volume read from the measuring cylinder.

Describe a practical method to measure the density of a regular object

Measure the mass with a scale. Divide this by the volume, found by multiplying the width, height, and depth measured with a ruler.

Explain why solids and liquids aren't compressible but gases are

The spaces between the particles in a solid or liquid are too small for them to move into, but these spaces are big enough in a gas, so the particles can flow into them.

Describe the findings of John Dalton and model and date

Elements consist of indivisible small particles All atoms of the same element are identical - different elements have different atoms Atoms can't be created or destroyed tiny solid sphere 1803

Describe the findings of J.J. Thompson + data

He made the "plum pudding" model, an atom consisting of electrons ("plums) in a positive charged "pudding". + 1897

Describe the findings of Ernest Rutherford + date

Geiger and Marsden were asked by Rutherford to fire positive alpha particle radiation at a thin sheet of gold foil to see how the particles were defected. They were expected to go straight through, but some were deflected, disproving the plum pudding model. The Rutherford Model (or Nuclear Model) contains a positively charged nucleus surrounded by electrons. Nucleus with overall positive charge and most mass of atom Electrons orbits nucleus in shells Most atom is empty space 1909

Describe the findings of Neil Bohr + 1911

The Bohr Model consists of a positively charged nucleus surrounded by electrons in orbits / fixed energy shells.

What happens in a single connected body of fluid with multiple surfaces?

The surfaces will all be at the same height. This is the surface level.

State the formula for liquid pressure

P = ρhg

State the formula for gas pressure

P = f / a

State the value of atmospheric pressure

100 kPa

What is upthrust?

The upward force felt by an object when submerged in a liquid or gas, which comes from the pressure exerted by the fluid. It is the resultant force when the force at the bottom is greater than the force at the top.

What is the difference between heat and temperature?

Heat is the total energy of all the particles in an object. Temperature measures the average energy of all the particles in an object.

What is heat capacity?

The energy needed to increase an object's temperature by 1 degree.

What is specific heat capacity?

The energy needed to increase 1kg of an object's temperature by 1 degree.

State the formula for specific heat capacity

Q = mcΔT

What is the specific heat capacity of water?

4200 J/kgC

What can you measure to calculate the specific heat capacity of an object?

The current and voltage (the product is the power), and the time (the product of the power and time is the energy transferred), the mass, the change in temperature.

State the differences between physical and chemical changes

Physical changes are reversible and don't produce any new substances. Molecules are re-arranged. Chemical changes are irreversible and produce new substances. The molecules change.

List the changes of state

Freezing, melting, evaporation, condensation, deposition (gas -> solid), sublimation (solid -> gas).

What happens to the mass in a change in state?

It is conserved as the number of particles remains the same.

Define latent heat

The energy needed for a substance to change state.

Define specific latent heat

The energy needed for 1 kg of a substance to change state.

What are the different types of specific latent heat?

Specific latent heat of fusion (melting), specific latent heat of vaporisation (evaporation).

State the formula for specific latent heat

Q = mL

Describe a practical method to measure the specific latent heat of ice

Clamp a funnel of ice above a beaker. Surround a heater with the ice and attach it to a DC power supply, ammeter, and voltmeter with copper wires. Measure the mass of the beaker with a scale. Turn on the power supply and take current and voltage readings. After a certain time, multiply all three values together. Divide this by the mass of the water in the beaker by taking a final mass reading and finding the difference from the original.

What causes an object to sink or float?

Denser objects have a greater downward force of weight. If this is greater than the force of upthrust, it will sink.

State the Archimedes principle

The upthrust exerted on a submerged object is the weight of the displaced liquid.

What produces gas pressure?

The particles exerting forces on the container walls during collisions.

How does temperature affect pressure?

As temperature increases, the speed of the particles increases, causing more collisions per second and an increased speed of collisions, so the force increases, so pressure increases.

What is the relationship between temperature and pressure?

Proportional in C, directly proportional in K. Absolute zero exists at the x-intercept.

State the value of absolute zero

-273 degrees Celsius

How do you calculate Kelvin from Celsius?

C + 273 = K

State the pressure law

The pressure divided by the temperature of a gas is a constant k.

When does the pressure law apply? and what is it

Constant volume of gas and fixed number of particles/molecules. Its when the pressure is directly proportional to the temperature

State Boyle's law

The pressure and volume of a gas are inversely proportional at a constant temperature.

State the equation that represents Boyle's law

P₁V₁ = P₂V₂

How does the temperature of a gas change when compressed?

When a gas is compressed, the moving wall does work on / transfers energy to the gas particles, increasing the average speed, increasing temperature. The kinetic energy of the plunger is transferred to thermal energy in the gas.

Explain why atmospheric pressure changes based on altitude

At sea level, there are more air particles exerting a downward force above, so atmospheric pressure is greater than at the top of a mountain for example.

what are the 2 units of measurement for pressure (gas) and convert between them.

n/msquared / Pa. 1pascal = 1 N/msquared

Bulb

Diode

LED

Fuse

Battery

LDR

Thermistor

Ammeter

Voltmeter

Motor

Resistor

Variable resistor

Open Switch

A.C. supply

Earth/Ground

Ohmmeter

Resistor

Lamp

D.C. supply

Diode

Closed switch

Which elements are magnetic materials?

Iron, nickel, and cobalt

What types of magnetics are made of magnetic materials?

Permanent magnets and induced magnets

What does a magnetic field of one magnet look like?

This.

What does a magnetic field between two like poles look like?

This.

What does a magnetic field between two opposite poles look like?

This.

What do the magnetic field lines represent?

The direction a north pole of a magnet would experience a force in.

What do closer lines represent?

A stronger force

What would happen to a small magnet in a magnetic field?

It would align with the field lines. The resultant force is 0 but there is a turning effect due to equal moments about the centre of mass in opposing directions.

What item uses this principle?

Compasses. They are small magnets that align to the Earth's magnetic field.

What happens to the atoms in magnetic materials?

They act as small magnets. When placed in a magnetic field, they all line up and the magnetic material becomes a temporary magnet. In a permanent magnet, they are always lined up.

What is a magnetic field?

What an electric field becomes when a charged object moves.

What is the magnetic property of particles called?

Intrinsic magnetic moment

Describe the earth's magnetic field

The north pole of a magnet is the north seeking pole as it points towards the earth magnetic north pole. The earth's magnetic north pole is its geographic south pole.

If a wire carries a current towards you, what is the direction of the field lines?

Anticlockwise

What rule can be used to find this?

The right hand screw rule

What factors affect magnetic field strength?

The magnitude of the current and distance from the wire.

What is the unit of magnetic field strength?

Teslas (T)

What is the strength of the Earth's magnetic field?

Roughly 0.01mT

What is the shape of the magnetic field in the centre of a current carrying loop of wire?

A straight line

State everyday uses of magnets

Fridge magnets, fridge doors (sealing mechanism), data storage in a computer system.

What is the shape of the magnetic field around a current-carrying wire?

A circle with the space between the field lines increasing as distance from the wire increases.

What is the symbol of the wire depending on its direction?

Dot if towards you, cross if away from you.

What happens if we reverse the current?

The magnetic field reverses in direction.

What happens if we increase the current?

The magnetic field strength increases.

What is a solenoid?

Many parallel loops of current carrying wire. Also called a coil.

What is the type of the magnetic field in the middle of a solenoid?

Uniform

What does the magnetic field around a solenoid look like?

This.

What does a solenoid have the same magnetic field as?

A bar magnet, as a solenoid is an electric bar magnet. Most electromagnets are solenoids.

How can you increase the strength of a solenoid?

Increase the current, add more coils, use a soft iron core.

Define soft iron

Iron that can be magnetised and demagnetised easily. Nothing to do with hardness.

State the uses for electromagnets.

Electronic doorbells, door locks, sorting and moving metal rubbish, MRI scanners.

What is the motor effect?

A current-carrying wire in a magnetic field feels a force due to the interaction between the two magnetic fields. This is maximised when the wire and field lines are perpendicular, but 0 when parallel.

How can we increase the magnitude of this force?

By increasing the current.