GSCE Physics Flashcards

Question

Transformer

Answer 1

Devices that can change p.d of alternating current Step-up increases p.d, Step-down reduces p.d Made from two coils of wire, primary coil from ac input, and secondary coil to ac output, coils are not electrically connected, both wound around iron core. Easily magnetised and can carry magnetic fields from primary coil to secondary. -primary coil connected to ac supply -primary p.d drives ac through primary coil -primary coil current produces a magnetic field, which changes as current changes -iron core increases strength of magnetic field -changing magnetic field induces a changing p.d in secondary coil -induced potential difference produces an alternating current in external Transfers can only work with alternating current risks: high voltages can be produced - insulate secondary coil, use very low voltages on primary coil

Answer 2

ratio of p.d on transformers coils matches ratio of numbers of turns on coil Energy is conserved Power on primary side= power on secondary side

Answer 3

Positive/negative All matter has charge Property of all matter that causes a force when near another charge Insulators don’t conduct charge as their electrons cannot flow throughout the material and are fixed Conductors can conduct charge as their electrons are delocalised and can flow instead of being fixed

Answer 4

Static charge only occurs when electrons build up on object two insulators rubbed together- electrons transferred from one to the other. become charged as the electrons cannot flow Protons do not move as they are tightly bound in the nuclei two conductors are rubbed- electrons will flow in and out of them which cancels any overall effect so they remain neutral. Conductors allow the electrons to flow away, forming an electric current Static charge can only build on on insulators When static charge on a object is discharged, an electric current flows through the air which causes sparks. Discharge happens when enough charge builds up and the objects are close but not touching, the charge flows through the air from a highly negative object to a highly positive object to balance out the charges

Answer 5

Charged objects experience electrostatic force Attractive or repulsive Non contact Greater charge and smaller separations result in greater force Force is proportional to the inverse square of distance

Answer 6

Charged object can attract an uncharged insulator Charged object repels another charged object Charged objects can attract small neutral objects near Positive/negative charge on object attract/repel electrons within small objects, induces charge inside them causing them to be attracted E.g balloons attract hair after being rubbed on a jumper, a stream of water will attractted by charged object due to induced attraction , two positively charged plastic robs repel, charged rod will attract bits of paper

Answer 7

All charged objects have an electric field Electric fields are created by electric charges Can be attractive or repulsive Exert forces on other charges Any object with a electric charge will feel a force in a electric field Closest where the field strength is greatest Stronger the charge, the more field lines and the stronger the force is felt Point in the direction away from positive charge towards negative charge Can be demonstrated by sprinkling semolina onto castor oil The particles of semolina line up in the fields generated by electro dies attached to a van de graaff generator

Answer 8

- lines drawn from pos to neg (arrows show force on a positive charge) - never cross - density of field lines on a diagram is indicative of the strength of the field - field gets weaker as distance from charge increases - arrows go out of the positive charge and into a negative charge.

Answer 9

Rate of flow of charge Needed for current to flow: source of p.d (e.g cell or battery) and a closed circuit that has a completed path for the charges to move through Charge = current x time Amps Measured at any point on circuit by Ammeter placed in series to component The current flowing through a component/in a circuit depends on its resistance and p.d across the component

Answer 10

Volts Energy transferred between two points in a circuit Voltmeter placed in parallel across a component One volt is the potential difference when one coulomb of charge transfers one joule of energy

Answer 11

Closed circuit where the current only follows a single path Only has one loop Current same everywhere P.d split between components, depends on resistance Energy is conserved in circuits so.. Total p.dis the sum of potential differences across the individual components and the same as the potential difference of the cell Total (net) resistance across all the components increases as more components are needed Total resistance is R1+R2+

Answer 12

Has more than one loop An electron will not pass through every component on its way round the circuit If a component breaks, the current can still flow around the circuit through another loop so rest components keep working Energy is conserved Voltage is the same across each branch Total current supplied is shared between components on different loops The net resistance decreases as more components are added as there are more paths for the current to flow through. Worked out by dividing p.d of cell by total current for the circuit

Answer 13

When a charge moves through a potential difference, electrical work is done and energy is transferred

Answer 14

Switch- turn circuit on (closed) and off (open) Lamp- electrical current heats filament in a bulb so it gives out light Fixed resistor- limits the flow of electrical current, has a resistance that does not change Variable resistor- resistance changed by moving the position of a slider. Used to limit and control flow of electric current Thermistor- resistance depends on its temperature. Low temp=high res, high temp= low re. Used in thermostats, heat-activated fire alarms Light-dependent resistor- resistance depends on light intensity. Low light= high res, high light= low res. Used in camera sensors, automatic security lights Semiconductor diode- allows current to flow in one direction only, used to convert alternating current into direct

Answer 15

Aim: to see how brightness of bulb change as they are connected in series/parallel, measure p.d and current across bulbs Method: - one bulb and a battery, series circuit, ammeter in series+voltmeter parallel with component, record if bulb is bright/dim, add another bulb into loop, record bulb’s brightness current and potential difference Evaluation- In series circuit, bulbs become dimmer as potential difference is shared equally across the bulb, current is same for all In parallel circuit, each branch shows the same potential difference so bulbs on one branch will have the same relative brightness, the current for each bulb will add up to the current near the battery Safety: Overheating components e.g bulb. Burned fingers, scorched desk. Use heatproof mat, switch off between readers to ensure components don’t get too hot. Blown bulb- shattered glass. never exceed max supply voltage

Answer 16

Electric wires are made of metal Atoms in a solid metal are arranged in a regular lattice structure. The outer electrons from each atom are free to move through the structure, forming a current However, they may collide with atoms or meet defects in the lattice which reduces the number of electrons flowing which reduces the current Conductors have a low resistance, insulators have high resistance Factors: heat, current, length of wire, thin/thick wire

Answer 17

Current flowing through a resistor is directly proportional to potential’s difference Provided the temperature remains constant

Answer 18

Difference for a resistor and filament bulb -ensure power supply is set to zero at the start -place variable resistor and fixed resistor in circuit -place voltmeter parallel to fixed resister and ammeter in series to it -record the readings -use the variable resistor to alter the p.d -record the new readings -repeat, increasing the p.d each time -repeat but with power supply reversed -repeat but replace fixed resistor with a bulb Evaluation: For a fixed resistor, the potential difference is directly proportional to the current, so doubling the amount of energy into the resistoe results in a current twice as fast through the resister. Ohm’s law. Fixed resistor is a ohmic conductor (it obeys ohms law). In a filament bulb, the current does not increase as fast as the potential difference. Doubling the amount of energy does not cause a current twice as fast. The more energy that is put into the bulb, the harder it is for the current to flow - the resistance of the bulb increases. As the p.d increases, the temperature of the thin wire inside the bulb does. Increases resistance of filament bulb.

Answer 19

Investigate relationship between current and p.d for a diode -diode mist be protected with a suitable protective resistor -set variable resistor to give the lowest potential difference -record readings on voltmeter and millimetre (ammeter that’s capable of reading to +1 mA) -alter variable resistor to increase potential difference by 0.2 V -record the new readings -repeat, increasing current each time -repeat, reverse power supply connections Evaluation: a semiconductor dioxide only allows current to flow in one direction. In one direction, the diode’s resistance is very large and no current will flow. In other direction, the diode’s resistance is smaller and current will flow.. in this direction, the diode’s resistance is very large at low potential differences. At high p.d, the resistance quickly drops and current begins to flow Health and safety: Heating of the resistance wire, burns to skin, do not touch resistance while whilst circuit is connected, allow time to cool

Answer 20

Power is the rate of transfer of energy between energy stores or rate work is done 1 watt= 1 joule per sec

Answer 21

As current increases: electrons have more energy. When these electrons flow through a resistor, they collide with the atoms in the resistor. This transfers energy to the atoms, causing them vibrate more, these increased vibrations make it more difficult for electrons to flow through the resistor, so resistance increases, and the current decreases ————————————————— Temperature: normal wires - increased atoms vibrations when hot. thermistor- resistance is lower at higher temperatures ——————————- Length- greater length, more resistance, lower current. Electrons have to make their way through more resistor atoms so it is harder than a shorter wire —————————- thinner/thick wires: thinner gives give greater resistance as less overall room for electrons to pass through atoms —————— Light: for LDR, a greater light intensity= lower resistance, so resistance is greatest when dark. ——————- Voltage: diode allows current to flow freely in one direction. In the opposite direction, they have a very high resistance so no current can flow.

Answer 22

A physical quantity is something that can be measured Scalar quantity has only magnitude e.g distance, speed Vector quantity has magnitude and direction e.g displacement (overall distance from a fixed point), velocity(total displacement/time)

Answer 23

When a body moves in a circle, it’s direction is constantly changing so it has a constantly changing velocity It must also be accelerating at some points. The force responsible for acceleration is centripetal force and it acts radially inwards towards the centre of the circle, it keeps the object moving in a circular path. E,g centripetal force due to friction between car’s tires and the road

Answer 24

Distance+ measure of how far an object moves small=ruler/tape measure/trundle wheel. Large= GPS/aerial photography for measurement Speed= rate of change of distance (distance travelled per unit time). Can be measured accurately with light gates

Answer 25

``` Average speed= total distance travelled/total time taken When no units assume: Distance=meters Average speed=m/s Time=seconds ```

Answer 26

``` Gradient=speed Steeper the gradient=faster speed If stationary= straight line ___ If constant speed= linear gradient line If accelerating= curves upwards If decelerating= curves downwards ```

Answer 27

Velocity=m/s Acceleration=m/s^2 Acceleration due to gravity is 10m/s^2 (resultant force =mass x acceleration due to gravity)

Answer 28

-set up ramp balanced on a wooden block at one end -mark out 30cm at each end of ramp. Avoid making ramp too steep (causes trolley to roll too quickly, makes measuring difficult) -release trolley from top of ramp, record time taken for it to reach the mark -repeat from top of ramp but record time taken for it to reach end -calculate speed Health and safety= trolley falling, injury to feet, keep feet away from end of ramp

Answer 29

``` Gradient= acceleration Area under graph=displacement A- accelerating B-constant C- decelerating D=stationary ```

Answer 30

Object remains in same state of motion unless a resultant force acts on it When resultant force is zero: stationary object stays stationary, moving object continues to move at same velocity Inertia= tendency of an object to continue in its current state (at rest or in uniform motion). Inertial mass= ratio of force over acceleration. How difficult it is to change the velocity of an object

Answer 31

Models forces acting on an object Resultant vector for two vectors at right angles Pythagoras theorem 4^2+3^2=_/25=5

Answer 32

Forces acting on a body are unbalanced the resultant force will NOT be zero and the object will speed up (accelerate), slow down (decelerate) or change direction. Force=mass x acceleration If no units assume: Force=newtons, mass=kg, acceleration=m/s^2 accerlation proportional to resultant force and inversely proportional to mass

Answer 33

When two objects interact, they exert equal and opposite forces on eachother

Answer 34

At terminal velocity, the object moves at steady speed in constant direction cuz resultant force is 0 Three stages of falling: -object accelerates downloads due to force of gravity -as it’s speed increases, frictional forces e.g air resistance/drag increase -at terminal velocity, the weight of the object due to gravity is balanced by the frictional forces and resultant force=0 -opening parachute, air resistance increases, skydiver slows down until new lower terminal velocity is reached

Answer 35

Product of mass and velocity Vector he mass of an object multiplied by its velocity. Momentum (kgm/s)= mass x velocity In a closed system: Total moment before an event=total momentum after the event (Conservation of momentum) Momentum is conserved in collisions and explosions ``` Calculate velocity from truck collision. Mass after collision=10kg 2kg trolley=2x3=6kgm/s 8kg trolley=8x0=0kgm/s Total momentum before collision=6+0=6kgm/s velocity=momentum/mass Velocity=6/10=0.6 ```

Answer 36

Work is done when energy is transferred from one store to another Also when force causes an object to move When work is done against frictional forces acting on an object, object’s temperature increases work done=force x distance

Answer 37

When a force acts on a object, object change shape by bending/stretching/compressing/combination of all To change shape of a stationary object, there must be more than one force acting Elastic deformation is reversed when force removed Plastic deformation is not fully reversed when force is removed - there is a permanent change in shape

Answer 38

Extension happens when object increases in length Compression happens when it decreases in length Extension is directly proportional to force applied E.g force doubled, extension doubles Elastic limit - when elastic object is stretched beyond its elastic limit, the object does not return to its original length when the force is removed Relationship between force and extension changes from linear to being non-linear

Answer 39

-secure clamp stand to bunch using G-clamp/large mass on base -use bosses to attach two clamps to the clamp stand -attach the spring to the top clamp, and a ruler to the bottom clamp -adjust the ruler so that is it vertical, and with its zero level with the top of the spring -measure and record unloaded length of the spring -have a 100g slotted mass carrier from the spring. Measure and record the new length of the spring -add 100g slotted mass to the carrier measure and record new length of spring -repeat Accuracy: keep ruler vertical Health and safety: equipment falling of table, heavy objects falling on feet could bruise or fracture, use a G-clamp to secure the stand, sharp end of spring recoiling if the spring sp breaks, damage to eyes, cuts to skin, wear eye protection, support and gently lower masses whilst loading the spring, masses falling to floor if the spring fails, heavy objects falling on feet could bruise or fracture, gently lower load onto spring and step back

Answer 40

All objects with mass have a gravitational field around them A gravitational field is where a mass experiences a force All matter has gravitational field that attracts other object more mass an object has, the greater it’s gravitational field N= kg x N/kg gravity Force (also known as weight)= mass x GFS GFS=10N/kg

Answer 41

Refers to gravity force of planets and other bodies and the effect it has on objects force that acts on a mass due to gravity when in gravitional field Weight of object and mass are directly proportional Non-contact force - Gravity exerts it’s force through a field Weight of an object can be measured using calibrat3d spring-balance (Newton meter)

Answer 42

When a object is lifted in a gravitational field, energy is transferred to a gravity store J= kg x m x N/kg GPE= mass x height x GFS

Answer 43

A force or system of forces may cause a object to turn A momen is the turning effect of a force Moments act about a point in a clockwise or anti-clockwise direction The point chosen could be any point on the object although is usually the pivot Moment of a force= force x distance Nm= N x m Distance is the perpendicular distance from pivot to the line of action of the force

Answer 44

If a object is balanced, the total clockwise moment about a pivot= total anti-clockwise moment

Answer 45

Consist of: pivot, effort, load Different types of levers: EPL (e.g scissors), PLE (e.g wheelbarrow), PEL (tweezers) Simple levers and rotation As effort is applied to rotate one end about the pivot, the opposite end is also rotated about the pivot in the same direction which has the effect of rotating/lifting the load Levers allow a larger force to act upon the load than is applied by effort Easier to move large or heavy objects The longer the lever, the further the effort acts from the pivot, the greater the force on the load, easier it is

Answer 46

Gears are wheels with toothed edges that rotate on an axle or shaft The teeth of one gear fit into the teeth of another gear which lets one gear turn the other Meaning one axle or shaft can be used to turn As one gear turns, the other must also turn Where gears meet, the teeth must both move in the same direction The forces acting on the teeth are identical for both gears but their moments are different If a larger gear is driven by a smaller gear, the large gear will rotate slowly but have a greater moment If a smaller gear is driven by a larger gear, the smaller gear will rotate quickly but have a smaller moment

Answer 47

Pressure is force per unit area Determines the effect of a force on a surface To increase pressure= increase force or reduce area the force acts on To reduce pressure= decrease force or increase area force acts on Calculating pressure Liquids and gases are fluids- pressure in fluids cause a force normal to a surface. A force that is normal to a surface acts at right angles to it Pressure= force normal to a surface/area of that surface Pa= N/m^2

Answer 48

A machine that uses liquid to transmit a force Pressure in liquid is the same everywhere in the system Simplest type is made of two pistons connected by liquid filled pipe If one piston is pushed, the force is transmitted through the liquid and the other piston moves Liquids are used as they are more difficult to compress than gases so are better at transmitting forces - when a force is applied at one end of the system, it is easy transferred through the system

Answer 49

Dalton’s model - tiny solid balls. Atoms cannot be broken down into anything simpler. The atoms of a given element are identical to eachother. Atoms of different elements are different from one another. During chemical reactions atoms rearrange to make different substances Thomson model- plum pudding. discovered negative charged electrons. Atoms are mass spheres of positive charge. Electrons are scattered around inside. Rutherford- nuclear model. Geiger marsden experiment tested plum pudding model. Aimed beams of positively charged alpha particles at thin gold foil sheet. Disapproved plum pudding model. Some alpha bounced back, passed, refracted. Means atoms are central positive charged nucleus with most of the mass. Electrons orbit the nucleus. Bohrs model- using mathematical ideas, showed that electrons occupy shells/energy levels around nucleus Atom is 1x10-10m Radius of nucleus is much smaller than the radius of atom

Answer 50

Mass per unit volume of a substance | MDV

Answer 51

All matter consists of particles including atoms and molecules Solids- particles are close together in a regular structure and vibrate around fixed position Liquids- particles are close together but free to move past each other randomly Gases- particles are far apart and move randomly in all directions Density of a substance changes when it changes state. It’s mass does not change. When solid to liquid, relatively small change in volume and density as particles still remain close together

Answer 52

Solid regular- top pan balance to record mass, ruler to measure length width height, calculate volume using low h, calculate density using MDV Solid irregular- top pan balance to recor mass, fill displacement can until water is level with bottom of pipe, place measuring cylinder under the pipe so ready to collect displaced water, drop object into can and wait until no more water runs into cylinder, measure the volume of displaced water, calculate density MDV Water- place empty measuring cylinder on top pan balance record mass, place liquid in measuring cylinder and measure new mass, record volume, mass of liquid= liquid in cylinder - empty cylinder on its own, calculate density MDV Suggestions for improvement: Top pan balance is only precise to +-1g, use a more precise balance Displacement can may not be set up correctly each time - another added drop of water would cause some tod ripple out of spout before use so check that no water comes out before placing measuring cylinder under spout Health and safety: water spilled from displacement can, spill and fall, work next to sink and have paper towels ready to mop up spills

Answer 53

Transferring energy to or from a substance can change its state The number of particles does not change during a change of state, only their spacing and arrangement Therefore conversation of mass Changing state is physical change as process can be reversed Chemical reaction is when changes cannot be reversed so easily

Answer 54

Temperature is the measure of the average e kinetic energy of particles in a substance Measured with thermometer or temperature sensor The higher the temperature, the higher the average kinetic energy Temperature does not show the energy store associated with an object How do energy and temperature differ? When energy is transferred by heating it can change the enety stored in system, change the physical state of the system, make chemical reactions occur When enery is transferred to water in liquid state, water molecules gain kinetic energy and speed up. The larger the mass of water, the more energy needed to raise the temperature by a given amount. This is because more molecules need to have their speed changed Change in temperature of a system depends on the amount of thermal energy transferred to the system, the mass of the substance and the nature of the substance itself

Answer 55

Measure of the amount of thermal energy needed to increase the temperature of 1kg of a substance by 1oC

Answer 56

Changing the internal energy of a material will cause it change temperature or change state The thermal energy to change the physical state is given by specific latent heat Specific latent heat of a substance is the amount of energy needed to change he state of 1kg of a substance without changing its temperature Each substance has two specific latent heat: Latent heat of fusion: amount of energy neeed to freeze or melt the substance at its melting point Latent heat of vaporisation: amount of energy needed to expose aye or condense the substance at its boiling point Latent heat of vaporisation is usually greater than fusion as it takes more energy to boil a substance than to melt it

Answer 57

- place immersion heater into the central hole at top of weighted metal block - connect heater in series with an ammeter and in parallel with voltmeter - place thermometer into smaller hole. Add two drops of oil into the hole to make sure the thermometer is surrounded by hot material - insulate the block by wrapping it with cotton wool - record the temperature of the block - connect the heater to the power supply - record current a potential difference - after 10 mins, turn heater off. The temperature will still rise even though the heater has been turned off and then it will begin to cool. Record the highest temperature that it reaches Health and safety: hot immersion heater and sample material, burnt skin, do not touch jester when switched on, position it away from edge of bench, allow time to cool before packing away equipment

Answer 58

Particles on a gas move very quickly in random directions Collisions frequently happen between particles, particles and the wall of the container, effect of collisions with the container is to produce a net force acting on the container walls, force acts at right angles to the container walls, which is detected as gas pressure, this pressure can be measured using a pressure gauge, collisions caused by a gas trapped inside a balloon causes forces to act outwards in all directions, giving the balloon its shape A closed system is a system where no substances can enter or leave P A gas in a closed system can be compressed by reducing its volume which increases its pressure Expanded by increasing its volume which decreases its pressure

Answer 59

Closed system: volume stays same, gas pressure increases as temp increases cuz gas particles travel faster. Collides with walls of container more frequently and with more force In a fixed volume of gas, pressure is proportional to temperature Abouslte zero (-273oC) where gas would have no pressure and particles would not be moving at all

Answer 60

Closed system= temp says same, gas pressure increases as volume decreases Same number of particles collide with walls of container more frequently as less space Particles collide with same amount of force (as temp says same) Boyle’s law : Experiment: trapped air bubble at sealed end of a J shaped tube using liquid mercury and then added more mercy and observed what happened to volume of air bubble discovered that higher the column of mercy in the left hand tube, the greater the force exerted on the trapped air, the smaller the bubble became as its pressure increased, Volume is inversely proportional to pressure E.g if volume of container halved, pressure doubled Pressure x volume= constant Pa x m^3

Answer 61

Atmosphere exerts pressure on the earth surface and objects placed in atmosphere Decreases as altitude (height above the surface of planet) increases as number of gas molecules in a given volume of air decreases, frequency of collisions with objects in the air decreases, the pressure decreases

Answer 62

Pressure can be increased: increase temp (increases frequency and force of collisions) decrease volume - increase frequency of collisions but not the force A force applied to the particles in a gas a causes a transfer of energy Work is done on the gas to compress it Work done= force x distance J= N x m Mechanical work transfers energy from the person or machine’s store of chemical energy to thermal energy store of the gas The volume of the gas decreases so the pressure increases, this is because the gas particles are moving in less space, so they collide with the container walls more often The moe rather of gas is not fixed in most applications and increased pressure leads to increase in temp so an increase in enety store of gas (kinetic energy) means temp must increase as it’s the measure of the average KE of particles

Answer 63

Particles in liquids close together Exert pressure by colliding w eachother and w objects and container walls Liquid pressure exerted equally in all directions Pressure increases w depth and density of liquid deeper object submerged in liquid, greater pressure. As particles in any part are being squashed by weight of liquid above them. Greater depth, greater weight of liquid above For a given volume of liquid, the greater density of the liquid, the greater it’s mass, when comparing the pressure in liquids of different densities the pressure is greater at the same height in the densest liquid because there is a greater weghr of liquid pushing down Pressure due to column of liquid = height of column x density of liquid x GFS Oa= m x kg/m^3 x N/kg

Answer 64

object partially submerged in liquid experiences upwards force (upthrust) float if upthrust=weight of object Sink if upthrust less than weight also depends on area+density of object

Answer 65

The total pressure exerted on any submerged object= liquid pressure + atmospheric pressure

Answer 66

Electrostatic- repulsion or attraction due to charge Gravity - all masses attract each other Magnetism - repulsion or attraction of magnets Normal contact force - repulsive force when two objects touch each other Friction - acts when two surfaces move past each other - always on the opposite direction to movement

Answer 67

Work is done when a spring is extended or compressed Work done is equal to elastic potential energy stored provided plastic deformation has not happened J=0.5 x n/m x m^2 J=0.5 x spring constant x extension^2