Physics Paper 1: Triple

Name ………………………………..

1. Energy stores and transfers

2. Conservation of Energy

3. Efficiency

4. Energy Resources

5. Advantages and Disadvantages of Energy Resources

6. Electrical Circuits

7. Electrical Components

8. Sensing Circuits

9. Electricity in the Home

10. Electrical Power and Charge

11. Isotopes and Nuclear Radiation

12. Particle Model

13. Particles in Gases

14. Maths in Science

15. Rearranging Equations

16. Equations

17. Required Practicals

Specific Heat Capacity

Thermal Insulation

Density

Resistance

V- I Characteristics

1. Energy stores and transfers Energy Stores

Chemical

Magnetic

Electrostatic

Nuclear

Thermal

Kinetic

Gravitational potential

Elastic potential

Energy Transfer

Energy is transferred between energy stores:

When a system changes energy is transferred.

This can be into or away from the system, be-

tween objects in a system or between different en-

ergy stores.

A closed system is where neither matter nor ener-

gy enters or leaves. The total energy change in a

closed system is zero (energy is not created or

destroyed).

Mechanically (a force)

Electrically (moving charges)

Particles (Sound, heating - conduction)

Radiation (light or sound)

Kinetic Store

All moving objects have energy in the kinetic

store.

The more mass an object has the more KE it

has.

The faster an object is going the more KE it has.

Ek = 1/2 mv2

Eg. A car has a mass of 3000kg is travelling at

20m/s. Calculate the energy in the KE store.

Ek = ½ x 3000 x 202 = 600 000 J

Energy Transfer by Doing Work

Throwing a ball upwards: Force from a per-

son does work – energy is transferred from the

chemical store of the person to the kinetic store

of the ball.

A ball is dropped: Energy is transferred from

the gravitational store to the kinetic store. The

gravitational force does work.

A car braking to slow down: The friction on

the brakes does work. Energy is transferred

from the cars kinetic store to the thermal store

of the surroundings.

Energy Transfer by Heating (eg.

kettle boiling)

1) The water is the system.

Energy is transferred by heating

to the waters thermal store.

2) A two object system (water and

heating element).

Energy is transferred to the ther-

mal store of the heating element

electrically. This is then trans-

ferred to the thermal store of the

water.

Elastic Potential Store

Stretching or squashing an objects

raises its elastic potential energy

store.

Calculates the elastic potential

energy of a spring if it has not ex-

ceeded its limit of proportionality.

Kinetic Energy

mass

mass

Conduction

This occurs in solid objects. When an object is heated, ther-

mal energy is transferred to the kinetic store of the particles.

This causes them to vibrate more and collide with other parti-

cles, so energy is transferred between the kinetic stores.

Convection

When particles are free to move (in a liquid and gas) an increase in their ki-

netic store causes them to move faster.

This means the space between the particles increases, so the density of the

area being heated decreases.

The warmer less dense region rises and the cooler, denser regions fall.

Specific Heat Capacity

A measure of the energy transferred to a thermal store of an object. It is the amount of energy needed to raise the temperature of 1kg sub-stance by 1°C. Different substances will need different amounts of energy to do this.

∆Θ= temperature change (°C)

c = specific heat capacity (J/kg°C)

∆E= change in thermal energy (J)

m = mass (kg)

Gravitational Potential Store

Is increased when objects are raised off the ground. The amount of energy depends on the mass and height of the object and strength of the

gravitational field it is in.

A falling object has energy transferred from its GPE store to a kinetic store.

If there is no air resistance the energy lost from the GPE store = energy gained in the KE store.

There is usually air resistance, so some energy will be transferred to other stores, such as the thermal store of the surroundings.

Ep = m x g x h

Gravitational field strength (N/kg)

Height

Mass (kg)

Gravitational Potential Energy (J)

E = m x c x Θ

2. Conservation of Energy Conservation of Energy

Energy can be transferred, stored or dissipated but never created or destroyed.

All energy is never transferred usefully. Some is always wasted (dissipated).

For example, energy is transferred electrically to a laptop but some is dissipat-

ed to the thermal store of the laptop.

Reducing Wasted Energy

Friction between two moving objects causes energy to

be dissipated to the thermal store. It can be reduced by

lubrication.

Insulation reduces energy transfer by heating. This is

useful in our homes to reduce heating costs:

Cavity wall insulation fills the air gap between the

inner and outer wall reducing heat loss by convec-

tion.

Loft insulation reduces heat loss by convection

Double-glazing creates an air gap between the two

panes of glass to reduce energy loss by conduction.

Draught excluders reduce energy loss by

convection when placed around windows and doors.

Reducing the temperature difference between

the inside and outside will also reduce energy transfer.

Power

This is the rate of doing work (per second) in Watts.

1 watt = 1 joule of energy transferred per second.

eg. calculate the power of a motor that uses 6000J of energy to lift an object for

20 seconds.

A more powerful device can transfer more energy in a given time, or, will trans-

fer the same amount of energy in a faster time.

For example, if we have two identical cars but one with a more powerful engine

race. The more powerful one will finish first – it will have transferred the same

amount of energy but in a quicker time.

P = E/t Power (W)

Energy (J)

Time (s)

3. Efficiency

Efficiency

An efficient device wastes less energy than a less efficient device. It can

be calculated as a decimal, or multiplied by 100 to give a percentage.

Eg. calculate the efficiency of a motor that has a power of 500W and

transfers 300W usefully.

Useful and wasted energy

Appliance Useful Energy Wasted Energy

Light bulb Light Heating the sur-

roundings

Hair Dryer Kinetic Energy of

the fan.

Heating of the air.

Sound of the motor.

Heating the hairdry-

er itself.

Electric Motor Kinetic Energy

Gravitational poten-

tial energy if lifting.

Heating motor and

surroundings.

Sound waves.

4. Energy Resources Non-renewable

These will run out one day. They are fossil fuels

(coal, oil and gas) or nuclear fuel (uranium and

plutonium). Fossil fuels are burned to provide

energy to produce electricity.

Renewable energy These will never run out.

They are being replaced at the same rate, or

faster, than they are being used up.

Uses for Heating

Non-renewables: Natural gas is the most

common fuel burned to heat water in our heating

systems. Coal can be burned in fireplaces.

Electric heaters usually use electricity produced

from a non-renewable source.

Renewables: Geothermal heat pumps can be

used to heat homes. Solar water heaters use

thermal energy from the sun to heat water. Bio-

fuels can also be used to produce heat for a

heating system.

Uses for Transport

Non-renewables: Petrol and diesel are made from oil and used to power vehicles

such as cars. Coal is used in steam trains to boil water to produce steam to power the

train.

Renewables: Some vehicles run on biofuels. Electric powered vehicles can be

powered by renewables, such as solar cells.

Limits of Using Renewables

- Costs lots of money to build new power plants. Fossil fuels are very cost effec-

tive. People would have to pay for new power plants through energy bills or taxes from

the government.

- Difficulty placing new power plants (they may spoil the landscape)

- Many are not reliable, such as wind power

- Improving reliability takes a lot of expensive research and takes a long time.

- Personal changes can be expensive. It is very costly to buy solar cells for your

house or a hybrid car

For these reasons we are dependent on non-renewable energy resources.

Bio-fuels

A renewable energy resource made from plants or animal dung. Are burned to produce

electricity.

Dependency on Fossil Fuels

Currently we depend on fossil fuels to meet energy demands:

- large increase in population size

- more appliances require electricity

Our electricity usage in the 21st century has decreased as appliance have be-

come more efficient.

Oil is used to produce petrol and diesel as fuels for vehicles. Gas is burned to

cook with and to produce heat in our homes.

We are trying to reduce our dependency on fossil fuels. By 2020 the UK aims

to produce 15% of energy from renewable resources.

People want more Renewable Energy

More people want to use energy produced by renewable

sources because they know:

- burning fossil fuels is damaging the environment

- it is better to learn to get by without renewables before

they run out

Governments have set targets for using renewables due to

pressure from other countries and the public. This puts

pressure on energy companies to make changes.

Electric and hybrid cars are becoming more popular.

5. Advantages and Disadvantages of Energy Resources Bio-fuels

Produced from plants or animal

dung. Are used in the same way as

fossil fuels – burned to produce

electricity or run vehicles.

Where plants are used they take in

CO2 through photosynthesis during

their lifetime. When burned this CO2

is released again so no net change

in the amount of CO2 in the atmos-

phere.

+ Carbon neutral (if plants are

grown at the same rate as being

burned).

+ Reliable as crops grow quickly

- High costs to refine the fuel

- Space for growing food taken up

- Forests cleared to make space –

decay and burned vegetation re-

lease CO2 and methane.

Wind Power

The blades turn a generator which produces electric-

ity.

+ No atmospheric pollution

+ No fuel costs and minimal running costs

+ No permanent damage to the landscape when

removed.

- Visual and noise pollution

- Cannot increase supply to match demand

- High initial costs

- Cannot generate electricity if there is too little wind

Hydro-electric Power

Water flows out of a dam through turbines,

producing electricity.

+ Can respond immediately to increased

demand

+ Reliable (except if there is a drought)

+ No fuel costs and minimal running costs

- Requires land to be flooded to create a

dam

- Loss of habitats

- Look unsightly when the reservoir dries

up

Tidal Barrages

A large dam built across an estuary that allows the water back out to sea at a controlled speed

through turbines.

+ No atmospheric pollution

+ No fuel costs and minimal running costs

- Visual pollution

- Difficulty providing access for boats

- Initial costs are high

Geothermal Power

Radioactive decay in the core heats rocks near the surface. This

can be used to generate electricity or heat buildings directly.

+ Reliable

+ No atmospheric pollution

- Few suitable locations (only possible in volcanic areas)

- High cost to build power station

Non-renewable

+ Reliable

+ Easy to increase supply to match demand

+ Fairly low fuel extraction costs

+ High energy output

- Running out

- Release CO2 which contributes to global warming

- Release SO2 which causes acid rain

- Coal mines spoil the landscape

- Oil spills

- Nuclear waste difficult to dispose of

Solar Cells

Generate electricity from sunlight.

+ No atmospheric pollution

+ In sunny countries they are reliable (during the day)

+ Useful for remote places not supplied by the national grid.

+ No fuel costs and minimal running costs

- Cannot increase supply to match demand

- High initial costs

Atmospheric pollution includes CO2 which contributes to global

warming and SO2 which causes acid rain.

6. Electrical Circuits Key terms

Current is the flow of electrical charge. Measured in Amps (A)

Ampere - The ampere is the standard unit of measure of electric current. It is sometimes written as Amp.

Potential difference is the force that pushes the charge around. Measured in volts (V).

Volt - The standard unit of measure for electric potential (voltage).

Resistance is something that slows down the flow of current. Measured in ohms (Ω).

Ohm - The standard unit of measure for resistance.

Resistor - A basic electronic component that prevents the flow of electric current.

Electric circuit - An electric circuit is a collection of electronic components connected by a conductive wire that allows for electric current to

flow.

Watt - The standard unit of measure used for electric power.

Series Circuits

Current is the same throughout

the circuit: I1 = I2 = …

Potential difference is shared

across the components: Vtotal = V1

+ V2 +…

Resistance adds up: Rtotal = R1 +

R2 + …

Parallel Circuits

Current is shared across the

components: Itotal = I1 + I2 +…

Potential difference is the same

across all components: V1 = V2 =…

Total resistance will fall if two or more

resistors are added in parallel.

7. Electrical Components Components

A V

Light Emitting

Diode (LED)

Ammeter

Voltmeter

Cell

Battery

Variable

Resistor

Closed

switch

Open

Switch

Filament Bulb

As the voltage increases the current increases.

This causes the filament to get hotter, meaning

the resistance increases. Therefore, as the

voltage continues to increase the current levels

off.

Resistor

At a constant temperature the current is

directly proportion to the voltage.

This means it obeys Ohm’s Law.

Diode

The current can only flow in one direc-

tion because a diode has a very high

resistance in the opposite direction.

8. Sensing Circuits

Sensing Circuits

The pd of the power supply is shared between the fixed resistor and the thermistor.

If the temperature increases then the resistance of the thermistor will decrease.

This means there will be a larger pd across the resistor and therefore the fan, which will go faster (fan and resistor

will always have the same pd as they are connected in parallel).

Connecting the component across the variable resistor (LDR or thermistor) will have the opposite effect.

When it is dark the resistance of the LDR will be low, meaning the pd across both the resistor and bulb will be high.

Therefore the bulb gets brighter as it gets darker.

An example with numbers:

9V

1V

8V

Low temperature = high resistance

of thermistor, so very low pd across

resistor. Only 1V also across fan so

it does not turn.

High temperature = low resistance of

thermistor, so high pd across resistor.

Also 7V across fan so it turns.

2V

7V

9V

Light Dependent Resistor (LDR)

Thermistor

As the light intensity increases the

resistance drops. This means more

current can flow.

Can be used in automatic night

lighting and outdoor security lights.

As the temperature increases the

resistance drops. This means

more current can flow.

Can be used as temperature de-

tectors, such as in car engines

and thermostats.

9. Electricity in the Home

AC

With alternating current (AC) the current constantly chang-

es direction. It is produced by an alternating voltage where

the positive and negative ends keep alternating.

The UK mains supply is AC at 230V. It has a frequency of

50Hz.

National Grid

A network of cables that connects power stations to con-

sumers.

A huge amount of power is needed. This is achieved with a

high pd but a low current. A high current would cause

the wires to heat up, wasting a lot of energy. It is cheaper

to increase the pd and keep the current low for a given

power output.

Meeting Demand

Power stations have to meet

the demand for electricity,

which varies during the day.

They usually run below maxi-

mum capacity so more elec-

tricity can be generated to meet

demand, such as during big

sporting events.

DC

With direct current (DC) the current always

flows in the same direction. Batteries pro-

duce a DC voltage.

Peak Potential

difference at

peak and trough

Live Wire

If you touch the live a large

pd is produced across your

body and the current flows

through you. This electric

shock can injure or kill

you.

A connection between the

live and earth creates a low

resistance path to earth

so a large current will flow.

This could cause a fire.

Electrical Wiring

Most electrical appliances are connected to

the mains with a three core cable (3 copper

wires coated in insulating plastic):

· Live (brown) – Provides the alternating

pd at 230V.

· Neutral (blue) – Completes the circuit

carrying the current out of the appliance

at 0V.

· Earth (green and yellow) – A safety fea-

ture. Prevents the appliance becoming

live if there is a fault so does not normally

carry a current. It is at 0V.

10. Electrical Power and Charge

Power

Energy in an electrical circuit is transferred by a moving charge. The

charge has to work against resistance, so work is done. Work done

is the same as energy transferred and depends upon power.

Appliances have a power rating, the maximum operating power.

An appliance with a lower power rating will be cheaper to run (less

energy transferred per second).

A higher power rating might not mean more energy is transferred

usefully. It could be less efficient than another appliance so only

transfer the same amount, or less, energy to useful stores.

E = Pt Time (s)

Power (W)

Energy

transferred (J)

Power Calculations

Power (W) depends upon the potential difference (V) and current (A):

Or, if the potential

difference is not known: P = IV P = I2R

Charge

Energy is supplied to the charge at a power source, ‘raising’ through a

potential.

Energy is given up by the charge at components as it falls through a

potential drop.

E = QV

Charge flow

(Coulombs, C)

Potential difference (V)

Energy (Joules, J)

11. Isotopes and Nuclear Radiation

Isotopes

Different forms of the same ele-

ment.

Isotopes of an element have the

same number of protons but a dif-

ferent number of neutrons:

All elements have isotopes but

there are only a few that are stable.

Others decay into other elements to

become more stable by giving out

radiation.

8 protons, 8 neutrons

8 protons, 10 neu-

Decay

Alpha decay causes the charge and

mass of the nucleus to decrease:

Beta decay causes the charge of the nu-

cleus to increase. When an electron is lost

a proton is changed into a neutron:

Gamma rays do not change the mass or

charge.

Uranium-238 → Thorium-234 + α particle

Carbon-14 → Nitrogen-14 + β particle

Half Life

The time taken for the number of radioactive nuclei in

an isotope to halve. Activity (the rate at which a

source decays) is measured in Becquerel’s Bq (1Bq

= 1 decay per second).

eg. if the initial activity of a sample is 320Bq what will

it be after two half-lives?

1 half life = 320 ÷ 2 = 160Bq

2 half lives = 160 ÷ 2 = 80Bq

As a % this is

(80 ÷ 320) x 100 = 25%

Finding half-life

from a graph:

- Mark where half

the activity level is.

- Find the corre-

sponding time

(1.8s in this exam-

ple)

Thomson carried out experiments and discovered the electron. This led him to suggest the plum pudding model of the atom. In this

model, the atom is a ball of positive charge with negative electrons embedded in it.

Rutherford showed that plum pudding model was wrong. Positively charged alpha particles were fired at thin gold foil. Most alpha parti-

cles went straight through the foil. But a few were scattered in different directions by. It showed that the mass of an atom was in the centre

(the nucleus) and the nucleus was positively charged. This was called the nuclear model.

Bohr suggested that electrons orbit the nucleus at specific distances in shells

Chadwick provided the evidence for neutrons, about 20 years after the nucleus was an accepted idea. This provided evidence for

isotopes.

Radioactive Decay

Type of particle Properties How ionising Uses

Alpha

α

alpha particle – two

protons and two

neutrons (helium

nuclei).

Can only travel a few cm in

air and are absorbed by a

sheet of paper.

Very Smoke alarms. The α-particles

ionises air particles, causing a

current to flow. Smoke will

bind to the ions, stopping the

current so the alarm sounds.

Beta

β

A fast moving elec-

tron.

Have no mass and a

charge of -1. Travel a few

meters in air and are ab-

sorbed by about 5mm of

aluminium.

Moderate Testing thickness of sheets of

metal.

Gamma

γ

Are electromagnetic

waves.

Usually pass through ma-

terials. Absorbed by thick

sheets of lead or several

meters of concrete.

Weakly See EM waves sheet.

12. Particle Model

Solids

Have strong forces between particles, holding

them close together in a fixed, regular arrange-

ment. The particles can only vibrate around

fixed positions.

Liquids

Have weaker forces between particles so alt-

hough the particles are close together they can

move over each other at low speeds in ran-

dom directions.

Gases

Have almost no forces between particles. Have

more energy and are free to move in random

directions and speeds.

Internal Energy – the energy stored by the particles in a sys-

tem

Heating a system increases the energy particles have in their

kinetic and potential energy stores.

A temperature change depends on the mass of substance,

what it is made from and the energy input (see specific heat

capacity). If the substance is heated enough particles can

have enough energy in their kinetic stores to break bonds

holding them together and so a change in state occurs.

Density

Measures how compact a substance is. Depends on the material and how

the particles are arranged.

Compressing a less dense material pushes the particles closer together.

The mass would not change (same number of particles) but the volume

would.

Density (kg/m

3)

Volume (m

3)

Mass (kg)

Specific Latent Heat – the energy needed to change the state of 1kg of a

substance

Bonds are formed, giving out en-ergy. Internal energy decreases but the temp. doesn’t until all the substance has changed state.

Bonds are broken, taking in en-

ergy. Internal energy increases

but the temp. doesn’t until all

the substance has changed

state.

Specific latent heat of fusion = melting or freezing.

Specific latent heat of vaporisation = evaporating, boiling or condens-

ing.

Gas Pressure

When the particles in a gas collide with the side of the

container they exert a force on it.

The pressure is the force exerted per unit of area. In a

sealed container the gas pressure is the total force of

all the particles on the area of the container walls.

Increasing the temperature increases pressure be-

cause particles have a larger kinetic energy store. This

means they move faster so collide with the sides more

often and with more momentum = a larger total force

exerted so increased pressure.

13. Particles in Gases Temperature

Energy is transferred to the kinetic stores of particles when the temperature is in-

creased.

The higher the temperature the higher the average energy of the particles. This

means the higher the energy the faster the particles move.

Work Done

Work is done when energy is transferred by applying a force.

Work done on a gas increases its internal energy. This can increase the tempera-

ture of the gas.

Pumping up a bike tyre does work mechanically. The gas exerts a force on the

plunger (due to pressure). To push the plunger down against this force work has

to be done. Energy is transferred to the kinetic stores of the gas particles, increas-

ing the temperature.

Pressure

For a sealed container the gas pressure is the total force of

all the particles per unit of area. Increasing the temperature

of the gas means particles have more energy so collide with

the sides of the container with more force. Therefore the gas

pressure is higher.

Decreasing the volume means particles are closer together

so hit the sides more often. Therefore the gas pressure is

higher.

Pressure (p) and volume (V) are inversely proportional (if

one increases the other decreases):

Volume

Gas pressure causes an outwards force at right angles to the wall of the

container.

The pressure of the air pushes on the outside of the container.

A change in pressure can cause a container to change shape. Eg. if a heli-

um balloon is released it rises. As it gets higher the atmospheric pressure

decreases, causing the balloon to expand until the pressure inside the bal-

loon equals the air. pressure again.

Balloon at ground

level. Internal and

external pressures are equal.

Balloon rising. Air pres-

sure decreases. Internal

pressure is greater so

balloon expands

14. Maths in Science

15. Rearranging equations

Example 1. Power = Energy/Time or P = E / t

Rearrange to make energy “E”, the subject.

In order to change the subject of, or rearrange, a formula items in the formula need to be arranged so a different variable is the subject. We

have to use inverse operations for example dividing is the inverse of multiplying.

Here are two examples of rearranging equations:

Example 2

v = u + at

Rearrange to make initial velocity “u”, the subject.

V = u + at

V-at = u + at –at

U = v-at Or V-at = u

P = E

Multiply both sides by t

P x t = E

the t’s cancel out

E = P x t Or P x t = E

t

t

P x t = E

t

x t

x t

The subject of a formula is the variable that is being worked out. It can be recognised as the letter on its own on one side of the equals sign.

For example, in Maths the formula for the area of a rectangle A = bh (area = base x height), the subject of the formula is A.

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ow

er

= (

cu

rre

nt)

2 ×

re

sis

tan

ce

P

= I

2R

21

e

ne

rgy t

ran

sfe

rre

d =

po

we

r ×

tim

e

E =

Pt

22

e

ne

rgy t

ran

sfe

rre

d =

ch

arg

e f

low

× p

ote

ntia

l d

iffe

ren

ce

E

= Q

V

23

d

en

sity =

ma

ss / v

olu

me

ρ

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Gra

vita

tio

na

l field

str

ength

, g (

= 9

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/kg),

will

alw

ays b

e g

ive

n in

th

e q

ue

stio

n.

17. Required Practicals

Specific Heat Capacity

Method

1. Measure and record the mass of the copper block in kg.

2. Place a heater in the larger hole in the block.

3. Connect the ammeter, power pack and heater in series.

4. Connect the voltmeter across the power pack in parallel.

5. Put the thermometer in this hole.

6. Switch the power pack to 12 V. Switch it on.

7. Record the ammeter and voltmeter readings. These shouldn’t change during the experiment.

8. Measure the temperature and switch on the stop clock.

9. Record the temperature every minute for 10 minutes (600 seconds).

10. Calculate the power of the heater in watts.

To do this, multiply the ammeter reading by the voltmeter reading.

11. Calculate the work done by the heater. To do this, multiply the time in seconds by the power of the heater.

12. Plot a graph of temperature in 0C against work done in J and draw a line of best fit. Take care as the beginning of the graph may be

curved.

The specific heat capacity is the heat capacity divided by the

mass of the block in kg.

IV— Work done

DV—temperature

CV—metal block

Voltmeter must

be connected in

parallel

Possible Errors

Heat is lost to the surroundings

Part of the emersion heater is outside the block

Thermometer is measuring the temperature of water and not the block

Thermal Insulation

IV – Time (s)

DV – Temperature Change

CV – Volume of water, material of insulation, starting temperature.

Method

1. Use the kettle to boil water. Put 200 ml of this hot water into a 250 ml beaker.

2. Use a piece of cardboard as a lid for the beaker. The cardboard must have a hole for

the thermometer.

3. Insert the thermometer through the hole in the cardboard lid so that its bulb is in the hot water.

4. Record the temperature of the water and start the stopwatch.

5. Record the temperature of the water every 5 minutes for 20 minutes.

6. Repeat steps 1‒5 using one or more layers of insulating material wrapped around the beaker.

Density

Regular shaped object Irregular shaped object Liquid

1. Measure the length, width and

height.

2. Measure the mass with an accurate

balance (scales).

3. Calculate and record the volumes

4. Calculate and record the densities

(mass ÷ volume).

1. Measure and record the mass of the sample.

2. Fill a measuring cylinder half-full with water.

(There needs to be enough water so that when

you put the solid into the water, the water will

cover the solid but will not rise above the top of

the measuring scale.)

3. With your eye level with the water’s surface,

measure the volume of water and record it.

4. Carefully place the solid material into the

container.

5. Measure and record the new volume of the

water.

1. Measure the mass of the empty

beaker.

2. Pour about 100 ml of liquid into

the measuring cylinder.

3. Measure and record the volume.

4. Pour this liquid into the beaker.

5. Measure and record the mass of

the beaker and liquid.

6. Calculate and record the volume

of the liquid.

7. Calculate the density of the liquid.

Resistance of a wire

IV – Resistance

DV – Length of Wire

CV – Material of the wire, voltage from power pack/battery, temperature – take the readings

immediately, Repeats to reduce the impact of outliers, Same material of wire, same diameter of

wire

Method Ammeter in series, voltmeter in parallel

Powerpack/ battery – same voltage each time

Named length of wire

Reading current and p.d.

Calculate resistance V = IR

Re-

peat with different lengths of wire

Res

ista

nce

Ω

Length of Wire m

Resistors in series

As more resistors are added in

series the total resistance will

increase.

Resistors in Parallel

As more resistors are added in parallel

the total resistance will decrease.

This is because resistors in parallel

have the same pd across them as the

power supply. Adding another loop to

the circuit means the current has more

than one way it has to go. Therefore

the total current around the circuit in-

creases. An increase in current

R = V/I

Possible Errors

Wire heating up and increasing resistance.

Incorrect reading of ammeter and voltmeter.

Internal resistance of equipment used.

V-I Characteristics

Fixed Resistor

At a constant temperature the current is directly

proportion to the voltage.

This means it obeys Ohm’s Law.

Filament Bulb

As the voltage increases the current increases.

This causes the filament to get hotter, meaning the

resistance increases. Therefore as the voltage

continues to increase the current levels off.

Diode

The current can only flow in one direction

because a diode has a very high resistance

in the opposite direction.

IV—Potential Difference (Volts)

DV—Current (Amps)

CV— Same components, voltage from power pack, temperature – take the readings, immediately, Repeats to reduce the impact of outliers.